'Illllli 


1  nun 
1 


INTERNATIONAL  CHEMICAL  SERIES 

H.  P.  TALBOT,  PH.D.,  CONSULTING  EDITOR 


TECHNICAL 
METHODS  OF  ANALYSIS 


PUBLISHERS     OF     BOOKS      F  O  B^ 

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TECHNICAL 
METHODS  OF  ANALYSIS 

AS  EMPLOYED  IN  THE  LABORATORIES 

OF 
ARTHUR  D.  LITTLE,  INC.,  CAMBRIDGE,  MASS. 


EDITED  BY 

ROGER  CASTLE  GRIFFIN 

Director  of  Analytical  Department 


FIRST  EDITION 
SECOND  IMPRESSION 


McGRAW-HILL  BOOK  COMPANY,  INC. 
NEW  YORK:  370  SEVENTH  AVENUE 

LONDON:  6  &  8  BOUVERIE  ST.,  E.  C.  4 
1921 


0-7 


COPYRIGHT,  1921,  BY  THE 
McGRAW-HILL  BOOK  COMPANY.  INC. 


THIS  BOOK  IS  AFFECTIONATELY 
DEDICATED  TO  THE  MEMORY  OF  MY  FATHER 

tll  (Stiffin 


4G0150 


PREFACE 


THIS  book  contains  a  representative  selection  of  analytical 
methods  which  have  been  adopted  as  standard  procedures  in 
a  large  commercial  laboratory  engaged  in  technical  analysis. 
With  very  few  exceptions  the  methods  here  given  have  been  used 
many  times  in  this  laboratory  and  have  been  proved  to  give  satis- 
factory results  in  the  hands  of  different  analysts.  In  certain 
cases  it  has  been  thought  best  to  include,  for  the  sake  of  complete- 
ness, certain  standard  procedures  which  have  not  been  thoroughly 
tested  in  our  laboratory  but  which  have,  nevertheless,  received 
official  recognition  from  an  authoritative  body  of  chemists.  Such 
a  case  is  the  Roese-Gottlieb  method  on  page  418. 

Endeavor  has  been  made  to  give  such  directions  in  each  pro- 
cedure that  any  one  reasonably  familiar  with  analytical  technique 
can  readily  follow  them.  A  certain  amount  of  cross  referencing 
has  been  necessary  on  account  of  economy  of  space  but,  in  order 
to  avoid  the  annoyance  caused  by  carrying  this  to  extremes,  the 
directions,  when  they  are  not  too  long,  have  been  repeated  in 
most  cases. 

No  attempt  has  been  made  to  give  experimental  data  to  show 
the  accuracy  of  the  method  nor  to  enter  into  the  theory  of  the 
procedure.  On  the  other  hand  in  many  cases  it  has  seemed 
advisable  to  give  brief  descriptions  of  the  properties  which  a 
given  material  should  normally  possess  and  sufficient  other  infor- 
mation to  enable  the  analyst  to  translate  his  results  into  practical 
language.  Certain  specifications  and  requirements  of  an  authori- 
tative nature  have  also  been  included. 

It  is  obviously  impossible  in  a  book  of  this  size  to  enter  all  the 
fields  of  analytical  chemistry.  Certain  classes  of  work,  such  as 
drugs,  alkaloids,  and  medicines,  have  been  omitted,  as  they  are  of 
interest  mainly  to  specialists  in  these  lines.  This  is  also  true  of 
the  rare  elements  and,  to  a  certain  extent,  of  gas  analysis.  The 
analysis  of  mineral  rocks,  glasses,  and  vitreous  materials  would 

vii 


viii  PREFACE 

require  a  book  in  itself.  The  present  book  is  not  intended  for  the 
specialist,  confining  himself  to  comparatively  narrow  limits.  It 
aims  rather  to  include  methods  which  are  typical  of  the  procedures 
employed  in  the  usual  commercial  analyses.  Certain  special 
methods  have  been  included,  when  not  too  long,  in  the  belief  that 
they  are  not  otherwise  readily  obtainable  and  that  they  illustrate 
procedures  which  may  be  applicable  to  other  problems.  The 
analyst  whose  particular  problem  is  not  covered  by  the  methods 
here  given  is  referred  to  the  bibliography  in  the  Appendix. 

Some  of  the  methods  herein  described  are  original.  By  far 
the  greater  number,  however,  have  been  obtained  from  other 
sources.  In  many  cases  they  have  been  adopted  without  change; 
others  have  been  modified  in  the  light  of  experience  gained  from 
their  use.  Since  the  collection  of  methods  has  been  built  up 
gradually  over  a  period  of  years  it  is  not  possible  in  every  case 
to  give  proper  credit  for  the  original  source.  The  methods  of  the 
Association  of  Official  Agricultural  Chemists  have  been  found 
particularly  valuable,  although  it  has  sometimes  seemed  more 
convenient  to  change  their  arrangement.  The  various  publica- 
tions of  the  United  States  Bureaus  at  Washington  have  also  been 
drawn  upon  freely. 

The  tables  in  the  Appendix  have  been  confined  strictly  to  those 
concerned  with  quantitative  chemical  analysis.  The  values  in 
these  tables  have  all  been  independently  calculated  from  the  1920 
International  Atomic  Weights.  Every  effort  has  been  made  to 
have  them  correct.  If  any  errors  should  be  discovered  the  editor 
will  be  grateful  to  those  who  bring  them  to  his  attention.  Refer- 
ences to  other  tables  are  given  in  the  text;  and  tables  of  properties, 
specific  gravity  tables,  etc.,  may  be  found  in  the  handbooks 
referred  to  in  the  bibliography  in  the  Appendix.  This  bibliography 
aims  to  include  at  least  one  authoritative  book  in  each  of  the  fields 
of  analytical  chemistry. 

Several  cuts  have  been  included  as  aids  to  the  description  of 
procedures.  Acknowledgment  is  made  for  certain  of  these  as 
follows:  Fig.  9,  American  Society  for  Testing  Materials,  Standard, 
Serial  D-21-16;  Fig.  10,  U.  S.  Bur.  Mines  Tech.  Paper  166, 
Petroleum  Technology  39;  Figs.  16,  17,  18,  19  and  20,  Paper  25, 
No.  15,  19-23  (1919);  Figs.  21,  22  and  23,  Bureau  of  Chem., 
Circular  107;  Figs.  27  and  28,  Am.  Soc.  Test.  Mat.,  Standard 


PREFACE  ix 

C-9-17;  Fig.  29,  courtesy  of  the  Fairbanks  Co.  The  table  of 
constants  of  oils,  fats  and  waxes  on  pages  232-239  was  prepared 
from  data  obtained  largely  from  Lewkowitsch:  "  Chemical 
Technology  and  Analysis  of  Oils,  Fats  and  .Waxes." 

The  editor  wishes  to  express  his  appreciation  to  Dr.  H.  P. 
Talbot  for  valuable  criticisms  and  suggestions  and  to  Dr.  R.  S. 
Williams  for  reading  part  of  the  manuscript.  Thanks  are  also 
especially  due  to  Dr.  C.  J.  West,  who  prepared  the  bibliography 
and  whose  aid  in  arranging  the  manuscript  and  reading  the  proof 
is  greatly  appreciated.  Mr.  H.  C.  Parish  and  Mrs.  Helen  B. 
Colson  also  rendered  valued  assistance  in  checking  the  numerical 
tables. 

ROGER  C.  GRIFFIN. 


CONTENTS 


CHAPTER  I 
REAGENTS 

Liquid  Reagents 1 

Standard  Volumetric  Solutions 6 

Indicators 12 

Care  of  Platinum 14 

Recovery  of  Platinum  Residues 16 

CHAPTER  II 

GENERAL  INORGANIC  ANALYSES 

Sulfur 17 

Fuming  Sulfuric  Acid  (Oleum) ,  17 

Alkalies 19 

Ammonium  Hydroxide 23 

Table  Salt 24 

Sodium  Nitrite 28 

Sodium  Sulfide 28 

Sodium  Silicate  (Water  Glass) 29 

Potassium  or  Sodium  Bichromate 30 

Cyanides  of  Potassium  and  Sodium 31 

Acetate  of  Lime 32 

Antimony  Sulfide 34 

Determination  of  Small  Amounts  of  Arsenic 35 

Determination  of  Potassium  in  Fertilizers,  etc 41 

Lead  Arsenate 46 

Bordeaux  Mixture 50 

Bordeaux  Mixture  with  Paris  Green  and  Lead  Arsenate 52 

Paris  Green 54 

Lime  Sulfur  Solution 59 

Corrosive  Sublimate  in  Medicated  Gauze 62 

Asbestos  Magnesia  Pipe  Covering 62 

xi 


xii  CONTENTS 

CHAPTER  III 
GENERAL  ORGANIC  ANALYSES 

PAGE 

Nitrogen 64 

Methyl  Alcohol 71 

Grain  Alcohol  or  Cologne  Spirits 74 

Formaldehyde  Solution 79 

Formic  Acid 81 

Acetic  Anhydride 82 

Glycerol 85 

Dextrin  or  British  Gum 91 

Albumin 93 

Tannic  Acid 95 

Indigo 97 

Nicotine  in  Tobacco  and  Tobacco  Extract 100 

Nicotine  Solution 103 

CHAPTER  IV 

ANALYSIS  OF  METALS 

Sampling  Iron  and  Steel * 106 

Carbon  Steel 107 

Alloy  Steel 116 

Pig  and  Cast  Iron 129 

Tin  in  Tin  Ores. 134 

Zinc  (Spelter) 137 

Zinc  Dust 141 

Brass  and  Bronze 142 

Nickel  Silver 152 

White  Metals 154 

Mercury  in  Zinc  Amalgam 163 

Testing  of  Galvanizing  or  Sheradizing  on  Iron  and  Steel 163 

Tinning  Test  for  Tinned  Iron  and  Steel 166 

CHAPTER  V 

ANALYSIS  OF  FUELS 

Coal  Sampling 167 

Coal,  Proximate  Analysis  and  Heating  Value 172 

Coal,  Ultimate  Analysis 180 

Phosphorus  in  Coal  and  Coke 184 

Coal  Ash  and  Refuse 185 

Gasoline 185 

Heating  Value  and  Sulfur  Content  of  Liquid  Fuels 190 


CONTENTS  xiii 

CHAPTER  VI 
ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS 

PAGE 

Turpentine 193 

Turpentine,  Electric  Railway  Specifications 196 

Lipseed  Oil 197 

Tung  Oil 198 

Mixed  Paints  and  Pigments  in  Oil 200 

Green  Graphite  Pole  Paint 207 

Red  Lead  and  Orange  Mineral 210 

White  Lead  (Basic  Carbonate) 211 

Chrome  Yellow 213 

Oil  Varnishes 217 

Japan  Driers 221 

Shellac  and  Shellac  Varnishes 223 

Black  Air  Drying  Insulating  Varnish  and  Black  Baking  Insulating  Varnish  227 

CHAPTER  VII 
ANALYSIS  OF  OILS,    FATS,  WAXES  AND  SOAPS 

Animal  and  Vegetable  Oils  and  Fats 230 

Lubricating  Oils 254 

Unsaponifiable  Matter  in  Oils '. 261 

Castor  Oil 263 

Sulfonated  Oils  (Turkey  Red  Oils) 263 

Lard  Oil. 265 

Olive  Oil 266 

Tallow 268 

Greases 270 

Degras  (Wool  Grease) 274 

Beeswax 275 

Paraffin  Wax 278 

Soap > 279 

CHAPTER  VIII 
ANALYSIS  OF  WOOD,  PAPER  AND  PAPER-MAKING  CHEMICALS 

Cellulose  in  Wood 289 

Wood  Pulp  Sampling  and  Testing 290 

Sulfate  Cook  Liquor 294 

Sulfite  Acid ; .  301 

Alum 303 

Aniline  Dyes 307 

Blanc  Fixe .  .  .308 


xiv  CONTENTS 

PAGE 

Bleach  (Bleaching  Powder) 312 

Bleach  Consumption  of  Pulp 313 

Casein 315 

Clay— for  Paper  Filler 318 

Crown  Filler , 319 

Glue 320 

Lime 324 

Limestone 327 

Rosin 327 

Rosin  Size  and  Rosin  Size  Milk 329 

Satin  White 332 

Talc — for  Paper  Filler 334 

Ultramarine 336 

Fibers  in  Paper 337 

Standard  Papers  for  Fiber  Analysis 339 

Chemical  Analysis  of  Paper 339 

Physical  Testing  of  Paper 345 

Sizing  in  Paper 355 

Tarnishing  Test  for  Paper 362 

Cotton  Cellulose  (Cotton  Linters)  for  Nitration 363 

Wood  Distillate  Products. .                                                                          .  368 


CHAPTER  IX 

ANALYSIS  OF  TEXTILES  AND  TEXTILE  FIBERS 

Structural  Analysis  of  Textile  Fabrics 372 

Fibers  in  Cloth  and  Yarns 377 

Chemical  Tests  on  Ropes  and  Twines 382 

Differentiation  of  Rope  and  Cordage  Fibers 383 

Asbestos  Cotton  Twine .  385 


CHAPTER  X 

ANALYSIS  OF  FOODSTUFFS 

Ammonia  in  Eggs , 387 

Coloring  Matter  in  Foods 389 

Crude  Fiber 393 

Sulfur  Dioxide  in  Foodstuffs 395 

Reducing  Sugars  and  Sucrose ...... 396 

Saccharine  Products 408 

Honey 420 

Maple  Products 424 

Butter  and  Butter  Substitutes, ,  .  427 


CONTENTS  XV 

PAGE 

Cocoa,  Chocolate  and  Cacao  Products 430 

Feed  Stuffs  and  Mixed  Grains 438 

Milk  and  Cream 443 

Condensed  or  Evaporated  Milk 449 

Cheese 451 

Vinegar 454 

Lemon  and  Orange  Extracts 458 

Orange  Oil  and  Lemon  Oil 464 

Oil  of  Peppermint 464 

Peppermint,  Spearmint,  and  Wintergreen  Extracts 467 

Vanilla  Extract..                                                                                           .  468 


CHAPTER  XI 

MISCELLANEOUS  ANALYSES 

Leather 474 

Chromium  in  Chrome  Salts  and  Leathers 477 

Sumac  Extract 479 

20%  Para  Rubber  Compound 480 

Case  Hardening  Compounds 484 

Cutting  Compounds 486 

Metal  Polishes 488 

Soldering  Paste 490 

Sanitary  Analysis  of  Water  and  Sewage 492 

Industrial  Water 514 

Boiler  Scale 522 

Fertilizers 524 

Carbolineum  and  Similar  Wood  Preserving  Oils 530 

Gypsy  Moth  Cresote 536 

Coal-Tar  Roofing  Pitch 536 

Bituminous  and  Asphaltic  Road  Binders 537 

Crude  Coal-Tar  and  Water-Gas  Tar 548 

Spent  Oxide 554 

Mortar  and  Concrete 559 

Sampling  and  Physical  Testing  of  Portland  Cement 561 

Chemical  Analysis  of  Portland  Cement 572 

Mechanical  Testing  of  Sand  and  Gravel 576 

TABLES: 

International  Atomic  Weights 584 

Molecular  and  Atomic  Group  Weights 586 

Analytical  Factors 608 

Volumetric  Solutions 615 

Bibliography 627 

Index .  635 


TECHNICAL 
METHODS  OF  ANALYSIS 


CHAPTER  I 
REAGENTS 

LIQUID  REAGENTS 

General. — In  making  up  reagents  always  use  chemicals  of 
highest  purity,  unless  otherwise  instructed.  In  the  following  direc- 
tions water  is  understood  to  be  distilled  water.  All  solutions 
should  be  filtered  unless  perfectly  clear  or  unless  directions  state 
to  the  contrary.  Formulas  here  given  are  generally  for  1  liter  of 
reagent.  The  ordinary  green  glass  acid  bottle  contains  about  2.5 
liters. 

Acetic  Acid,  Glacial  —  Contains  99.5%  HC2H302.  The  sp.  gr. 
is  about  1.058. 

Acetic  Acid,  Dilute  (sp.  gr.  1.044). — Mix  400  cc.  of  glacial  acetic 
acid  with  1  liter  of  water.  This  solution  contains  about  30% 
of  HC2H302. 

Alcoholic  Potash  (Half -normal). — Dissolve  29  grams  of  pure 
KOH  (preferably  purified  by  alcohol)  in  1  liter  of  95%  alcohol. 

NOTE. — The  alcohol  before  use  should  be  tested  with  a  little  NaOH  and  if  it 
gives  a  decidedly  yellow  solution,  showing  an  excessive  aldehyde  content, 
treat  it  as  follows:  Dissolve  about  1.5  grams  of  AgNOa  in  3  cc.  of  water  and 
add  to  1  liter  of  the  alcohol.  Shake  thoroughly.  Dissolve  3  grams  of  NaOH 
in  15  cc.  of  warm  alcohol,  cool  and  add  to  the  main  solution.  Shake  thor- 
oughly, let  settle,  siphon  off  the  clear  liquid  and  distill,  adding  a  few  pieces  of 
pumice  to  prevent  bumping. 

The  alcohol  and  KOH  mixture  should  be  allowed  to  stand 
until  all  the  KOH  has  dissolved  and  then  filtered  rapidly,  or 
siphoned  off,  to  remove  the  insoluble  carbonate. 


2.  if.:  TECHNICAL  METHODS  OF  ANALYSIS 


,^^  \ilumina  -Or  earn.  —  Prepare  a  cold  saturated  solution  of  alum 
'  (KAl'1  snilfate)  i  in  water.  Add  NH4OH  with  constant  stirring 
until  the  solution  is  alkaline  to  litmus;  let  settle  and  wash  by 
decantation  with  water  until  the  wash  water  gives  only  a  slight 
test  for  sulfate  with  BaCk.  Pour  off  the  excess  of  water  and 
store  the  residual  cream  in  a  stoppered  bottle. 

Ammonium  Acetate.  —  To  1250  cc.  of  glacial  acetic  acid  add 
cautiously  1000  cc.  of  cone.  NH4OH  (sp.  gr.  0.90),  a  little  at  a 
time,  with  constant  stirring,  and  cooling  if  necessary.  The  solu- 
tion contains  about  70%  of  ammonium  acetate,  NIL^HaC^. 

Ammonium  Carbonate.  —  Dissolve  250  grams  of  ammonium 
carbonate  crystals  in  1  liter  of  water  and  add  100  cc.  of  cone. 
NILiOH.  This  solution  contains  about  22%  of  the  carbonate, 
which  is  generally  assigned  the  formula  (NH^COa-NHtCC^NH^. 

Ammonium  Chloride  (10%).  —  Dissolve  100  grams  of  NHjCl 
in  water  in  a  liter  volumetric  flask  and  dilute  to  the  mark. 

Ammonium  Hydroxide,  Cone.  (sp.  gr.  0.90).  —  The  solution 
contains  28-29%  of  NHs  by  weight. 

Ammonium  Hydroxide,  Dilute  (sp.  gr.  0.96).  —  Mix  400  cc.  of 
cone.  NE^OH  with  700  cc.  of  water.  The  solution  contains  about 
10%  of  NHa  by  weight. 

Ammonium  Molybdate.  Solution  No.  1.  —  Weigh  113  grams  of 
100%  c.  P.  molybdic  acid  (MoOs)  or  an  equivalent  amount  of 
weaker  acid.  Add  300  cc.  of  water,  175  cc.  of  cone.  NIL^OH, 
and,  after  mixing,  add  slowly  with  stirring  75  cc.  of  cone.  HNOs. 

Solution  No.  2.—  To  1200  cc.  of  water  add  500  cc.  of  cone. 
HN03. 

When  both  solutions  are  perfectly  cold,  pour  No.  1  into  No.  2 
(do  not  pour  No.  2  into  No.  1).  Add  5  cc.  of  (NH^HPO* 
reagent,  shake  well,  let  stand  until  clear  and  filter.  This  reagent 
contains  about  8%  of  ammonium  molybdate,  (NH 

Ammonium  Nitrate   (20%}.  —  Dissolve  200  grams  of 
in  water  and  make  up  to  1  liter. 

Ammonium      Oxalate      (4%)-  —  Dissolve      40      grams      of 
2O4-2H2O  in  water  and  make  up  to  1  liter. 


NOTE.  —  The  percentage  strength  of  this  solution  refers  to  the  crystallized 
salt  and  not  to  the  actual  content  of  (NH4)2C2O4.  This  note  also  applies 
to  other  reagents,  here  given,  which  are  made  from  chemicals  containing 
water  of  crystallization. 


REAGENTS  3 

Ammonium  Phosphate  (10%}. — Dissolve  100  grams  of 
(NH4)2HPO4  in  water  and  dilute  to  1  liter. 

Ammonium  Sulfate  (25%}.— Dissolve  250  grams  of  (NH4)2S04 
in  water  and  dilute  to  1  liter. 

Ammonium  Sulfide  (Colorless). — Pass  H2S  gas  into  750  cc.  of 
cone.  NHUOH  until  saturated.  Then  add  500  cc.  more  of  cone. 
NILtOH  and  1000  cc.  of  water. 

Ammonium  Polysulfide  (Yellow). — Make  up  a  bottle  of  color- 
less (NH4)2S  as  above,  add  to  it  50-75  grams  of  powdered  sulfur, 
and  shake. 

Barium  Chloride  (10%).— Dissolve  100  grams  of  BaCl2-2H2O 
in  water  and  dilute  to  1  liter. 

Barium  Hydroxide  (5%).  —  Dissolve  50  grams  of 
Ba(OH)2-8H2O  in  water  and  dilute  to  1  liter. 

Calcium  Chloride  (10%).— Dissolve  100  grams  of  CaCl2-6H2O 
in  water  and  dilute  to  1  liter. 

Calcium  Hydroxide  (Lime  Water). — Make  a  saturated  solution 
of  Ca"(OH)2  and  keep  tightly  stoppered.  Decant  or  filter  before 
use. 

Fehling's  Copper  Solution  (Soxhlet  Modification). — Dissolve 
69.28  grams  of  CuSC>4-5H20  in  water,  dilute  to  1  liter  and  filter 
through  prepared  asbestos. 

Fehling's  Alkaline  Tartrate  Solution  (Soxhlet  Modification). — 
Dissolve  346  grams  of  Rochelle  salts  (NaK  tartrate)  and  100  grams 
of  NaOH  in  water  and  dilute  to  1  liter;  let  stand  for  two  days 
and  filter  through  prepared  asbestos. 

NOTE. — The  two  above  solutions  are  also  used  in  the  Munson  and  Walker 
Method. 

Fehling's  Copper  Solution  (Allihn's  Modification). — Same  as 
Soxhlet  modification. 

Fehling's  Alkaline  Tartrate  Solution  (Allihn's  Modification). — 
Dissolve  346  grams  of  Rochelle  salts  and  250  grams  of  KOH  in 
water  and  dilute  to  1  liter. 

Ferric  Chloride  (10%).— Dissolve  100  grams  of  FeCl3-6H2O  in 
water  and  dilute  to  1  liter. 

Hydrochloric  Acid,  Cone.  (sp.  gr.  1.18-1.19). — This  reagent 
contains  35.5-37.5%  of  HC1  by  weight. 

Hydrochloric  Acid}  Dilute  (sp.  gr.  1.12). — Mix  500  cc.  of  cone. 


4  TECHNICAL  METHODS  OF  ANALYSIS 

HC1  with  400  cc.  of  water.     The  solution  contains  about  20% 
of  HCL 

Lead  Acetate,  Basic. — Boil  for  0.5  hour  430  grams  of  normal 
lead  acetate,  130  grams  of  litharge  (PbO)  and  1  liter  of  water. 
Let  cool  and  settle.  Dilute  the  supernatant  liquid  to  sp.  gr.  1.25 
(room  temperature)  with  freshly  boiled  water. 

NOTE. — U.  S.  P.  lead  subacetate  solution  may  also  be  used  in  place  of 

the  above  solution. 

'-  *' 

Lead  Acetate,  Normal  (10%). — Dissolve  100  grams  of 
Pb(C2H302)2-3H2O  in  water  and  dilute  to  1  liter. 

Magnesium  Ammonium  Chloride  (Magnesia  Mixture). — Dis- 
solve 90  grams  of  MgCl2-6H20  (or  45  grams  anhydrous  MgCb) 
and  240  grams  of  NILiCl  in  1  liter  of  water,  and  add  50  cc.  of  cone. 
NHiOH.  Ten  cc.  of  this  solution  will  precipitate  about  0.25  gram 
of  H3PO4  or  0.18  gram  of  P2O5. 

Magnesia  Wash  Solution  (for  washing  magnesium  ammonium 
phosphate  precipitate). — Dissolve  100  grams  of  NELiNOs  in  water, 
add  335  cc.  of  cone.  NELiOH,  and  dilute  to  1  liter. 

Mercuric  Chloride  (5%}. — Dissolve  50  grams  of  HgCl2  in 
water  and  dilute  to  1  liter. 

Nitric  Acid,  Cone.  (sp.  gr.  1.42). — This  reagent  contains 
69-70%  of  HNO3. 

Nitric  Acid,  Dilute  (sp.  gr.  1.20). — Dilute  400  cc.  of  cone. 
HNO3  with  600  cc.  of  water.  This  reagent  contains  about  32% 
of  HNO3. 

Nitric  Acid,  Red  Fuming  (sp.  gr.  1.80).— This  is  cone.  HNO3 
saturated  with  nitrogen  peroxide.  (Not  to  be  made  up  in  the 
laboratory.) 

Potassium  Bichromate  (4%). — Dissolve  40  grams  of  K^C^O? 
in  water  and  dilute  to  1  liter. 

Potassium  Ferricyanide  (1  %)  .—Dissolve  10  grams  of  K3Fe(CN)e 
in  water  and  dilute  to  1  liter. 

Potassium    Ferrocyanide    (1.5%}. — Dissolve    15    grams    of 
K4Fe(CN)6-3H20  in  water  and  dilute  to  1  liter. 

Potassium  Sulfocyanate  (Thiocyanate)  (1%). — Dissolve  10 
grams  of  KSCN  in  water  and  dilute  to  1  liter. 

Silver    Nitrate    (2.5%}. — Dissolve    25    grams    of    crystallized 


REAGENTS  5 

AgNOs  in  water  and  dilute  to  1  liter.  The  solution  should  be 
kept  in  dark-Colored  glass-stoppered  bottles. 

Sodium  Carbonate  (15%}. — Dissolve  150  grams  of  anhydrous 
Na2COs  in  water  and  dilute  to  1  liter.  It  is  best  not  to  keep  it  in 
a  glass-stoppered  bottle.  (Use  a  clean  rubber  stopper.) 

Sodium  Hydroxide  (10%).— Dissolve  100  grams  of  NaOH 
(electrolytic)  in  water  and  dilute  to  1  liter.  It  should  be  kept  in  a 
bottle  stoppered  with  a  clean  rubber  stopper  and  not  exposed  to 
the  air  any  more  than  necessary. 

Sodium  Phosphate  (10%). — Dissolve  100  grams  of 
Na2HPO4'12H2O  in  water  and  dilute  to  1  liter. 

Sulfuric  Acid,  Cone.  (sp.  gr.  1.84,  or  66°  Be\).— This  reagent 
contains  about  94%  of  H2SO4. 

Sulfuric  Acid,  Dilute. — Into  800  cc.  of  water  pour  cautiously 
200  cc.  of  cone.  H2SO4,  with  constant  stirring.  This  solution 
contains  about  30%  of  H2SC>4. 

Wijs  Solution  for  Iodine  Number. — This  solution  may  be  pre- 
pared in  two  ways: 

(1)  Dissolve  separately  7.9  grams  of  iodine  trichloride  and  8.7 
grams  of  sublimed  iodine  in  glacial  acetic  acid  by  warming  gently 
on  the  water  bath,  carefully  covered  to  prevent  absorption  of 
water.     Then  pour  both  solutions  into  a  liter  volumetric  flask, 
rinsing  the  containers  into  the   flask  with  glacial  acetic  acid. 
Dilute  to  the  mark  with  glacial  acetic  acid  at  20°  C. 

(2)  Dissolve  13  grams  of  resublimed  iodine  in  1000  cc.  of  pure 
glacial  acetic  acid.     Titrate  25  cc.  with  0.1  Nthiosulfate.     Remove 
another  25  cc.  to  a  small  flask.     Pass  washed  and  dried  chlorine 
gas  into  -the  main  volume  until  the  original  thiosulfate  titration 
is  just  doubled.     Then  add  the  small  amount  of  original  solution 
to  neutralize  any  possible  free  chlorine. 

Preserve  in  amber-colored  glass-stoppered  bottles  sealed  with 
paraffin  until  ready  for  use. 

NOTE. — Moisture  spoils  Wijs  Solution.  In  making  up  by  the  second 
method,  the  chlorine  must  be  passed  through  a  washing  bottle  containing 
water  and  then  through  two  bottles  containing  cone.  H2SO4. 


TECHNICAL  METHODS  OF  ANALYSIS 


STANDARD  VOLUMETRIC  SOLUTIONS 

General. — The  solutions  which  are  to  be  kept  in  stock  for 
general  laboratory  use  are  the  following: 

0.5  N  Hydrochloric  Acid 

0.1  N  Hydrochloric  Acid 

0.1  N  Potassium  or  Sodium  Hydroxide 

0.1  N  Oxalic  Acid 

0.1  N  Potassium  Permanganate 

0.1  N  Sodium  Thiosulfate 

0.1  N  Iodine 

0.1  N  Potassium  Bichromate 

0.1  N  Silver  Nitrate 

0.1  N  Sulfocyanate 

0.1  N  Arsenious  Acid 

In  making  up  standard  solutions  all  weighings  must  be  madf 
with  standardized  weights  and  all  volumetric  apparatus  (pipettes, 
burettes,  and  flasks)  must  have  been  calibrated  carefully  at  20°  C. 
In  titrating  standard  solutions  the  burettes  should  be  allowed  to 
drain  at  least  three  minutes  before  cheeking  the  reading  and 
proper  calibration  corrections  must  be  made. 

It  is  not  necessary  to  have  the  solutions  precisely  0.1  or  0.5 
normal,  provided  the  exact  strength  is  known.  The  strength  of 
the  solution  is  expressed  in  terms  of  a  "  factor."  This  "  factor  " 
is  the  ratio  between  a  given  number  of  cc.  of  the  solution  in  question 
and  the  number  of  cc.  qf  a  theoretically  correct  solution.  In 
other  words,  if  50  cc.  of  a  given  solution  of  NaOH  are  neutralized 
by  45  cc.  of  exactly  0.1  N  HC1,  then  the  NaOH  solution  has  a  fac- 
tor of  0.900  which  is  obtained  by  dividing  45  by  50.  In  using 
factor  solutions  the  number  of  cubic  centimeters  of  the  solution 
in  question  used  in  titrating,  multiplied  by  its  factor,  gives  the 
corresponding  number  of  cc.  of  a  solution  of  correct  strength. 

All  standard  solutions  for  the  laboratory  are  to  be  made  up 
at  20°  C.  or  made  up  at  a  known  temperature  and  the  "  factors  " 
corrected  to  20°  C.  (A  table  of  corrections  is  given  on  page  13.) 
The  "  factors  "  of  these  solutions  should  in  no  case  be  greater 
than  1.005  or  less  than  0.995.  The  factor  of  each  solution  should 


REAGENTS  7 

be  determined  at  intervals  not  exceeding  one  month  and  the  figures 
entered  in  a  record  book  kept  for  that  purpose  and  also  on  the 
label  of  the  bottle.  Each  solution  should  be  titrated  by  two  chem- 
ists independently  and  their  results  must  agree  satisfactorily  and 
be  accepted  before  the  solution  is  released  for  use. 

0.5  N  Hydrochloric  Acid.— (18.235  grams  absolute  HC1  per 
liter  or  about  43.0  cc.  of  cone.  HC1,  sp.gr.  1.20.) 

STANDARDIZATION. — Make  up  the  desired  amount  of  solution, 
mix  thoroughly  and  standardize  against  pure  Na2C03. 

The  sodium  carbonate  is  best  prepared  by  heating  sodium 
bicarbonate  *  of  the  highest  purity  by  one  of  the  following  two 
methods : 

I.  Half  fill  a  platinum  dish  with  pure  powdered  NaHCOs, 
place  it  in  an  air  bath  already  heated  to  about  200°  C.  and  raise  the 
temperature  to  270-280°  (never  more  than  300°).     Let  remain 
at  this  temperature  0.5  hour,  then  cool  in  a  desiccator  and,  before 
quite  cold,  transfer  to  a  warm,  dry,  stoppered  tube  or  bottle,  out 
of  which  it  may  be  weighed  rapidly  when  wanted.     For  each 
standardization  of  0.5  N  acid  weigh  out  accurately  about  1.1 
grams  of  the  resulting  Na2COs. 

II.  Accurately  weigh  a  platinum  crucible  and  place  in  it  about 
1.75  grams  of  pure  NaHCOs.     Place  in  an  asbestos  disc  with  a  hole 
cut  in  it  which  will  admit  the  crucible  to  about  half  its  depth. 
Cover  the  crucible  and  heat  at  a  temperature  which  will  just  give  a 
very  dull  red  on  the  bottom.     Continue  the  heating  for  at  least  0.5 
hour,   cool  in  a  desiccator  and  weigh  accurately  the  resulting 
Na2CO3. 

After  the  Na2COs  is  prepared  (it  should  be  anhydrous  and  free 
from  lumps),  dissolve  the  accurately  weighed  portion  in  about 
100  cc.  of  water,  add  2  drops  of  methyl  orange  and  titrate  with  the 
acid  to  the  point  where  the  color  changes  from  yellow  to  pinkish 
orange.  For  very  accurate  work  the  end  point  should  be  matched 
against  the  color  of  100  cc.  of  distilled  water  saturated  with  CO2 
and  containing  2  drops  of  methyl  orange  solution. 

CALCULATION. — 1  gram  of  pure  Na2COs  is  equivalent  to 
37.736  cc.  0.5  N  acid. 

*  The  sodium  bicarbonate  used  for  this  purpose  should  be  used,  for  no 
other.  Before  use  it  must  be  carefully  tested  and  its  purity  ascertained. 
The  bottle  should  then  be  labeled  "for  standardizing  purposes  only." 


TECHNICAL  METHODS  OF  ANALYSIS 

If    A  =  weight  of  Na2CO3  taken, 

B  =  cc.  of  HC1  (titration), 
and    F  =  the  factor  of  the  solution, 
37.732  A 


then    F  = 


B 


The  solution  should  be  so  made  up  that  F  is  greater  than  1. 
Add  the  required  amount  of  distilled  water  to  make  the  solution 
exactly  0.5  N,  mix  thoroughly  and  re-standardize  the  fresh  solu- 
tion as  above. 

EXAMPLE. — If  the  factor  is  1.042,  then  for  each  liter  of  the 
solution  there  should  be  added  42  cc.  of  water. 

0.1  N  Hydrochloric  Acid. — (3.647  grams  hydrogen  chloride  per 
liter  or  about  8.45  cc.  of  cone.  HC1.) 

STANDARDIZATION. — Follow  the  same  method   as  for  0.5  N 
HC1;    dissolve  about   1  gram  of  Na2COs   (accurately  weighed) 
in  500  cc.  of  water  in  an  accurate  volumetric  flask,  pipette  out  100 
cc.  of  this  diluted  solution  with  an  accurate  pipette  and   titrate ' 
with  the  0.1  N  HC1. 

0.1  N  Caustic.— (5.611  grams  KOH  or  4.001  grams  NaOH  per 
liter.  Weigh  out  about  5.8  grams  of  stick  KOH  or  4.2  grams  of 
stick  NaOH  for  each  liter  of  solution.) 

STANDARDIZATION. — Pipette  out  -50  cc.  of  the  solution  and 
titrate  against  0.1  N  HC1,  using  two  drops  of  methyl  orange  indi- 
cator. Titrate  a  second  50  cc.  portion  with  phenolphthalein 
indicator.  The  factor  for  each  indicator  should  be  written  on  the 
bottle.  The  factor  is  obtained  by  multiplying  the  factor  of  the 
0.1  N  HC1  by  the  number  of  cc.  of  the  latter  used  in  titration  and 
dividing  by  50  the  figure  thus  obtained. 

0.1  N  Oxalic  Acid.— (6.303  grams  H2C2O4-2H2O  per  liter.) 

STANDARDIZATION. — Pipette  out  50  cc.  of  the  solution  and 
titrate  with  0.1  N  caustic  and  phenolphthalein.  Multiply  the  num- 
ber of  cc.  of  0.1  N  caustic  used  in  the  titration  by  its  phenol- 
phthalein factor  and  divide  by  50  to  obtain  the  factor  of  the  solution. 

NOTE. — This  solution  may  also  be  standardized  against  0.1  N  KMnO4 
solution.  It  should  be  kept  in  a  dark-colored  bottle  away  from  light. 

0.1  N  Potassium  Permanganate. — (3.161  grams  KMn04  per 
liter.) ' 

NOTE. — The  KMnO4  should  be  dissolved  in  a  small  amount  of  distilled 


REAGENTS  9 

and  filtered  through  glass  wool  or  a  Gooch  crucible  with  an  asbestos 
mat  before  diluting  to  proper  volume.  This  solution  should  be  kept  in  a 
dark-colored  bottle  away  from  light. 

STANDARDIZATION. — Weigh  out  accurately  6.700  grams  of 
pure,  freshly  dried  sodium  oxalate.  Dissolve  in  250-300  cc.  of 
hot  distilled  water.  Transfer  to  a  liter  volumetric  flask  and  make 
up  to  volume  at  20°  C.  This  solution  will  be  exactly  0.1  N. 

Pipette  out  50  cc.  of  the  above  solution  into  an  Erlenmeyer 
flask.  Add  5  cc.  of  cone.  H2SO4  and  heat  to  boiling.  Titrate 
immediately  with  the  KMnC>4  solution,  adding  the  latter  drop  by 
drop  at  first.  The  first  appearance  of  a  faint  but  permanent 
pink  color  shall  be  taken  as  the  end  point.  To  obtain  the  factor 
of  the  KMnCX  solution,  divide  50  cc.  by  the  number  of  cc.  of 
KMn04  required  for  the  titration. 

1st  Optional  Method. — Pipette  out  50  cc.  of  0.1  N  oxalic  acid 
solution  and  add  50  cc.  of  distilled  water  and  5  cc.  of  cone.  H^SCX; 
heat  to  boiling  and  titrate  with  the  KMnO4  solution  until  a  perma- 
nent pink  color  forms.  Multiply  the  factor  of  the  0.1  N  oxalic 
acid  solution  by  50  and  divide  by  the  number  of  cc.  of  KMnO4 
used,  to  obtain  the  factor  of  the  latter. 

2d  Optional  Method. — Weigh  out  1.9607  grams  of  pure  ferrous 
ammonium  sulfate,  Fe(NH4) 2(804)2-61120.  Dissolve  in  100  cc. 
of  distilled  water,  add  5  cc.  of  cone.  H2SO4,  cool  and  titrate  imme- 
diately with  the  KMnO4  solution  until  a  permanent  pink  color  is 
formed.  The  factor  is  obtained  by  dividing  by  50  the  number  of 
cc.  of  KMnO4  solution  used. 

0.1  N  Sodium  Thiosulf ate.— (24.820  grams  Na2S2O3-5H2O  per 
liter.) 

STANDARDIZATION. — Standardize  the  solution  against  0.1  N 
K2Cr20?  solution  as  follows:  Weigh  out  accurately  4.9033 
grams  of  c.  P.,  freshly  dried  K^C^O?,  dissolve  in  about  200  cc. 
of  distilled  water  and  make  up  to  volume  in  a  liter  graduated 
flask  at  20°  C.  This  will  make  a  0.1  N  solution.  Place  in  a 
350  cc.  glass-stoppered  bottle  100  cc.  of  distilled  water  and  30  cc. 
of  10  per  cent  KI  solution.  Then  add  from  an  accurate  pipette 
50  cc.  of  the  above  bichromate  solution  followed  by  about  7  cc. 
of  cone.  HC1.  Shake  and  let  stand  for  three  minutes.  Cool 
under  the  tap  so  that  when  the  stopper  is  removed  any  adhering 
liquid  will  be  sucked  in.  Wash  the  stopper  carefully,  and  titrate 


10  TECHNICAL  METHODS  OF  ANALYSIS 

the  contents  of  the  bottle  with  thiosulfate  solution.  When  the 
yellow  color  of  iodine  has  almost  disappeared,  add  about  1  cc.  of 
starch  solution  and  continue  the  titration  until  the  deep  blue  color 
of  the  solution  changes  to  sea-green.  By  conducting  the  titration 
carefully  this  change  should  be  brought  about  by  a  single  drop  of 
thiosulfate  solution. 

Divide  the  number  of  cc.  of  bichromate  solution  taken  (i.e. 
50  cc.),  by  the  number  of  cc.  of  thiosulfate  required  for  the  titra- 
tion. The  quotient  will  be  the  factor  of  the  0.1  N  thiosulfate. 

Optional  Method. — Standardize  the  solution  against  0.1  N 
KMn04  solution  as  follows:  Place  in  a  350  cc.  glass-stoppered 
flask  or  bottle  150  cc.  of  distilled  water  containing  5  cc.  of  cone. 
H2S04;  cool  thoroughly  and  then  add  25  cc.  of  10%  KI  solution. 
Then  pipette  into  this  mixture  50  cc.  of  0.1  N  KMnC>4  solution. 
Stopper  the  flask  and  let  stand  ten  minutes;  then  titrate  the  iodine 
set  free  with  0.1  N  Na2S2Os  solution,  using  starch  indicator,  but 
not  adding  the  latter  until  the  iodine  color  has  nearly  disappeared. 
The  final  disappearance  of  the  blue  color  is  the  end  point.  To 
obtain  the  factor,  multiply  the  factor  of  the  0.1  N  KMnC>4  solution 
by  50  and  divide  this  result  by  the  number  of  cc.  of  0.1  N  thio- 
sulfate used  in  the  titration. 

0.1  N  Iodine. — (12.692  grams  sublimed  iodine  per  liter.) 

NOTE. — This  solution  should  be  kept  in  a  dark-colored  bottle  away  from 
light. 

Weigh  out  12.7  grams  of  iodine  for  each  liter  of  solution.  Also 
weigh  out  (for  each  liter)  20-25  grams  of  pure  KI  and  dissolve  in  as 
little  water  as  possible.  Then  add  the  iodine  and  after  it  has  dis- 
solved make  up  to  the  proper  volume. 

STANDARDIZATION. — Pipette  out  50  cc.  of  0.1  N  thiosulfate 
solution  and  titrate  with  the  iodine  solution,  using  starch  indi- 
cator, until  a  permanent  blue  color  forms.  In  this  case  the  starch 
may  be  added  directly  at  the  beginning  of  the  titration.  The 
factor  is  obtained  by  multiplying  the  factor  of  the  0.1  N  thiosulfate 
solution  by  50  and  dividing  the  result  by  the  number  of  cc.  of 
iodine  solution  required  for  titration. 

0.1  N  Potassium  Bichromate. — (4.9033  grams  K^C^O?  per 
liter.) 

NOTE. — This  salt  can  be  obtained  in  very  pure  condition  and  when  made 
up  accurately  should  give  a  0.1  N  solution. 


REAGENTS  11 

STANDARDIZATION. — Pipette  50  cc.  of  the  solution  into  a 
350  cc.  glass-stoppered  flask  or  bottle;  add  150  cc.  of  water  and 
5  cc.  of  cone.  H2SO4  and  after  cooling  thoroughly  add  25  cc.  of 
10%  KI  solution.  Stopper  the  flask  and  let  stand  ten  minutes, 
then  titrate  the  iodine  set  free  with  0.1  N  thiosulfate  solution, 
using  starch  indicator  but  not  adding  it  until  the  yellow  color  of 
the  iodine  has  nearly  disappeared.  The  end  point  is  denoted 
by  the  change  in  color  of  the  solution  from  deep  blue  to  light 
green.  The  factor  is  obtained  by  multiplying  the  number  of  cc.  of 
thiosulfate  solution  used  by  its  factor  and  dividing  the  result  by  50. 

0.1  N  Silver  Nitrate.— (16.989  grams  AgNO3  per  liter.) 

.STANDARDIZATION. — Pipette  out  25  cc.  of  the  solution,  dilute 
to  about  250  cc.,  add  a  slight  excess  of  dil.  HC1  and  let  stand  until 
clear.  Filter  the  AgCl  on  a  weighed  Gooch  crucible ;  wash  with  an 
extremely  dilute  solution  of  HC1,  and  finally  once  with  cold  dis- 
tilled water.  Dry  at  110°  C.  Place  the  Gooch  crucible  in  a  large 
platinum  crucible  and  ignite  gently  until  the  edges  of  the  precipi- 
tate just  begin  to  fuse.  Cool  and  weigh  the  AgCl. 

The  factor  of  the  solution  is  obtained  by  dividing  the  weight 
of  AgCl  found  by  0.3584. 

0,1  N  Sulfocyanate.— (9.717  grams  KSCN  or  7.611  grams 
NH4SCN  per  liter.) 

STANDARDIZATION. — Pipette  50  cc.  of  0.1  N  AgNOs  solution  into 
a  white  porcelain  dish  and  add  100  cc.  of  water,  5  cc.  of  dil.  HNOs 
and  5  cc.  of  ferric  nitrate  solution.  The  latter  should  be  approx- 
imately a  10%  solution  and  free  from  chlorides  (see  page  12). 
Titrate  with  0.1  N  sulfocyanate  solution  until  a  permanent  red 
coloration  of  the  liquid  appears.  (This  is  best  seen  by  artificial 
light.)  The  factor  is  obtained  by  multiplying  the  factor  of  the 
0.1  N  AgNOs  solution  by  50  and  dividing  the  product  by  the 
number  of  cc.  of  sulfocyanate  solution  required  in  the  titration. 

0.1  N  Arsenious  Acid. — (4.948  grams  As20s  per  liter.)  Dis- 
solve 4.96  grams  of  the  purest  sublimed  As2Os  powder  in  about 
250  cc.  of  distilled  water  in  which  has  been  dissolved  about  20 
grams  of  pure  Na2CC>3.  The  mixture  needs  warming  and  shaking 
for  some  time  in  order  to  complete  the  solution.  When  the  solu- 
tion is  clear,  cool  and  make  up  to  1  liter  at  20°  C. 

STANDARDIZATION. — Pipette  out  50  cc.  into  a  beaker,  dilute 
with  100  cc.  of  distilled  water  and  titrate  with  0.1  N  iodine,  using 


12  TECHNICAL  METHODS  OF  ANALYSIS 

starch  indicator.  The  starch  should  not  be  added,  however,  till 
near  the  end  of  the  titration.  The  factor  is  obtained  by  multi- 
plying the  number  of  cc.  of  0.1  N  iodine  solution  used  by  its  factor 
and  dividing  the  product  by  50. 

INDICATORS 

The  following  indicator  solutions  should  be  kept  in  stock: 

Methyl  Orange 

Methyl  Red 

Phenolphthalein 

Starch 

Potassium  or  Sodium  Chromate 

Ferric  Nitrate 

These  are  to  be  made  up  as  follows: 

Methyl  Orange. — Dissolve  1  gram  in  distilled  water  and  dilute 
to  1  liter. 

Methyl  Red.— Dissolve  1  gram  in  100  cc.  of  95%  alcohol. 

Phenolphthalein. — Dissolve  5  grams  in  500  cc.  of  50%  alcohol. 
Since  this  solution  will  be  slightly  acid,  it  must  be  neutralized  by 
adding  0.01  N  alkali  cautiously  till  a  faint  pink  color  appears, 
then  just  removing  the  color  with  a  drop  or  two  of  0.01  N  acid. 

Starch. — Triturate  5  grams  of  arrowroot  starch  with  a  little 
cold  water  and  then  add,  with  constant  stirring,  1000  cc.  of  boiling 
water.  Set  aside  to  cool  and  then  decant,  or  better  filter.  Add 
2  cc.  of  Oil  of  Cassia  or  of  CHCls  as  a  preservative. 

NOTE. — So-called  "soluble  starch"  must  not  be  used  as  an  indicator. 

Potassium  or  Sodium  Chromate. — Dissolve  25  grams  of 
K2Cr04  or  21  grams  of  Na2Cr04  in  a  small  amount  of  distilled 
water.  Add  a  drop  or  two  of  AgNOs  solution  to  remove  any 
chloride  (sufficient  AgNO3  must  be  added  to  form  a  brick-red 
precipitate),  filter  and  dilute  to  250  cc. 

Ferric  Nitrate.— Dissolve  10  grams  of  Fe(NO3)3-9H2O  in 
distilled  water,  add  a  few  drops  of  dil.  HNOs  and  make  up  to  about 
100  cc.  A  portion  of  this  solution  should  be  tested  with  AgNOa 
solution  to  make  sure  that  it  contains  no  chloride. 

NOTE. — Instead  of  ferric  nitrate,  the  solution  may  be  made  up  from  ferric 
alum,  Fe2(NH4)2(SO4)4-24H2O.  To  this  solution  should  be  added  a  little  cone. 


REAGENTS 


13 


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14  TECHNICAL  METHODS  OF  ANALYSIS 

HNO3.     It  should  be  kept  in  an  amber-colored  bottle  and  not  exposed 
to  the  air. 

REFERENCE. — Sutton:  "  Volumetric  Analysis." 

CARE  OF  PLATINUM 

Cleaning  Platinum  Ware. — Every  careful  analyst  necessarily 
uses  clean  apparatus.  The  habit  of  cleaning  and  polishing 
platinum  dishes  and  crucibles  immediately  after  using  is  easily 
formed  and  repays  the  user  with  increased  confidence  in  his  work 
as  well  as  in  the  prolonged  life  of  the  article. 

Rubbing  the  surface  of  platinum  with  moist  sea  sand  (round 
grains  only),  applied  with  the  fingers,  will  remove  most  impurities 
and  polishes  the  metal  without  appreciable  loss. 

Fusing  potassium  bisulfate  or  borax  in  the  dish  and  then 
boiling  in  water  and  polishing  as  above  with  sand  gives  a  clean 
bright  surface.  When  it  is  desired  to  clean  the  outer  surface  of 
dishes  in  this  manner,  they  must  be  placed  in  dishes  of  sufficient 
size  to  allow  the  fused  flux  to  envelope  completely  the  article  to 
be  cleaned. 

Sodium  amalgam  possesses  the  property  of  wetting  platinum 
without  amalgamating  with  it,  even  when  other  metals  are  pur- 
posely added  to  the  amalgam.  This  substance  is,  therefore,  use- 
ful for  effecting  a  quick  and  thorough  cleansing  of  platinum.  The 
amalgam  is  gently  rubbed  upon  the  metal  with  a  cloth  and  then 
moistened  with  water,  which  oxidizes  the  sodium  and  leaves  the 
mercury  free  to  alloy  with  foreign  metals.  The  mercury  is  then 
wiped  off  and  the  dish  cleaned  and  polished  with  sand,  as  above 
described. 

Stains  may  often  be  removed  from  platinum  ware  by  heating 
to  redness  and  then  dropping  into  the  dish  a  pinch  of  dry  NE^Cl. 

If  the  existence  of  a  base  metal  alloyed  with  the  platinum  is 
suspected,  immerse  the  article  in  question  first  in  boiling  HC1 
for  a  few  minutes,  then,  after  thorough  rinsing  with  clean 
water,  immerse  in  boiling  HNOs  free  from  chlorine.  If  the  dish 
is  unaffected  in  weight  or  appearance,  and  the  acid  baths  fail  to 
give  reaction  for  the  base  metals,  their  absence  in  appreciable 
quantities  is  assured. 

Notes  upon  the  Use  and  Care  of  Platinum  Ware. — It  is  impor- 
tant to  remember  that,  although  platinum  is  not  oxidized  in  the 


REAGENTS  15 

air  at  any  temperature,  nor  attacked  by  any  single  acid,  there 
are  many  substances  that  attack  and  combine  with  it  at  com- 
paratively low  temperatures. 

The  caustic  alkalies,  the  alkaline  earths,  nitrates  and  cyanides, 
and  especially  the  hydroxides  of  barium  and  lithium,  attack 
platinum  at  a  red  heat,  although  the  alkaline  carbonates  have  no 
effect  at  the  highest  temperatures.  Sulfur,  in  the  absence  of 
alkalies,  has  no  action,  but  phosphorus  and  arsenic  attack  plat- 
inum when  heated  with  it. 

The  ignition  in  a  platinum  crucible  of  precipitated  ammonium 
magnesium  phosphate  in  contact  with  carbon  derived  from  the 
filter  paper,  especially  when  the  precipitate  has  not  been  perfectly 
dried,  is  likely  to  result  in  the  reduction  of  sufficient  phosphorus 
to  render  the  platinum  very  brittle.  Similar  results  attend  the 
ignition  of  phosphates  in  general  in  the  presence  of  reducing  agents, 
and  great  care  should  therefore  be  taken  in  this  respect,  since  a 
very  small  phosphorus  content  may  ruin  platinum  ware. 

Platinum  in  spongy  or  finely  divided  form  is  energetically 
attacked  by  fused  sodium  peroxide,  and  platinum  crucibles  with- 
stand but  few  fusions  of  this  compound. 

Contact  with  compounds  of  the  easily  reducible  metals  is 
especially  dangerous  at  high  temperatures,  as  alloys  with  platinum 
having  a  low  fusing  point  are  readily  formed.  This  is  especially 
true  of  lead. 

Direct  contact  of  platinum  with  burning  charcoal  should  be 
avoided,  since  the  silicon  reduced  from  the  charcoal  ash  unites 
with  platinum,  making  it  brittle  and  easily  cracked. 

Heating  a  platinum  crucible  with  alcohol  lamps  is  preferable 
to  the  use  of  ordinary  gas.  When  gas  is  used,  care  should  be 
taken  to  have  the  supply  of  air  sufficient  to  insure  complete 
combustion,  since,  with  the  flame  containing  free  carbon,  the 
platinum  suffers  deterioration  by  the  formation  of  a  -carbide  of 
platinum,  which,  oxidizing  later,  blisters  the  metal.  For  this 
reason,  also,  the  inner  cone  of  a  reducing  flame  should  not  come  in 
contact  with  the  platinum. 

The  effect  of  the  Bunsen  flame  upon  the  surface  of  platinum 
exposed  to  its  action  produces  the  familiar  gray  appearance  which 
cannot  be  removed  except  by  burnishing.  Platinum  triangles 
often  become  gray  and  very  brittle  from  the  same  cause.  System- 


16  TECHNICAL  METHODS  OF  ANALYSIS 

atic  applications  of  moist  sand  to  all  articles  affected  in  this  way, 
after  use,  will  keep  them  in  good  condition  and  materially  prolong 
their  life,  with  but  a  trifling  loss  in  weight. 

RECOVERY  OF  PLATINUM  RESIDUES 

If  the  residues  consist  entirely  of  water-soluble  platinum  salts, 
evaporate  to  dryness  in  a  porcelain  dish  to  remove  alcohol  and 
then  take  up  in  water.  If  the  residues  contain  metallic  platinum, 
asbestos  shreds,  or  other  insoluble  solids,  evaporate  to  dryness, 
and  treat  with  aqua  regia  (1  part  cone.  HNOs  and  3  parts  cone. 
HC1)  until  all  the  platinum  is  in  solution.  Then  evaporate  to 
dryness,  warm  with  a  little  dil.  HC1  and  take  up  with  water. 
Filter  and  wash  the  residue  free  from  Pt  salts,  saving  the  filtrate. 

Prepare  a  solution  of  NaOH  of  sp.  gr.  1.2  and  add  to  it  8% 
of  glycerine.  Heat  this  liquid  to  boiling  and  pour  into  it  the 
clear  Pt  solution.  This  precipitates  the  Pt,  which  is  washed  with 
water,  then  with  HC1  and  again  with  water.  Dry  and  ignite  in  a 
porcelain  crucible  and  weigh.  Transfer  to  a  flask  and  cover  with 
water.  Add  aqua  regia,  in  small  amounts  at  a  time,  with  con- 
tinuous gentle  heating  on  the  water  bath.  Evaporate  in  a  por- 
celain dish  to  a  syrup.  Continue  to  evaporate  alternately  with 
HC1  and  with  water  until  no  more  nitrous  fumes  are  given  off. 
It  is  very  important  to  have  all  HNOs  removed.  The  solution  is 
always  intensely  brown,  due  to  the  presence  of  more  or  less  H^PtCU- 
To  convert  this  into  H^PtCle  saturate  the  fairly  warm  solution 
with  chlorine  gas  until  it  becomes  yellow.  Evaporate  to  a  syrup 
to  remove  the  chlorine;  dilute  somewhat  and  filter.  If  there  is 
much  insoluble  matter  it  should  be  filtered  off,  ignited  and  weighed, 
and  this  weight  subtracted  from  the  original  weight.  Then  dilute 
the  filtered  solution  until  it  contains  10  grams  of  Pt  per  100  cc. 
(or  if  desired,  it  may  be  made  up  to  any  other  known  strength). 

REFERENCE. — Treadwell-Hall:  "  Analytical  Chemistry,"  Volume  1,  page 
236. 


CHAPTER  II 

GENERAL  INORGANIC  ANALYSES 
SULFUR 

General. — For  ordinary  purposes  the  only  necessary  determina- 
tions on  sulfur  or  brimstone  are  moisture,  ash,  and  the  amount  of 
sulfur. 

Moisture. — Grind  the  sample  and  weigh  out  2-5  grams  in  a 
flat-bottomed  dish.  Dry  to  constant  weight  at  a  temperature  not 
exceeding  105°  C.  Report  the  loss  as  moisture. 

Sulfur. — Dissolve  the  residue  from  the  moisture  determination 
in  CS2.  Filter  through  a  weighed  Gooch  crucible,  which  has 
previously  been  treated  with  a  little  CS2.  Wash  the  residue  with 
€82  and  then  with  a  little  ether.  Dry  and  weigh.  Subtract 
from  100%  the  sum  of  the  percentage  insoluble  in  CS2  and  the 
percentage  of  water  and  report  the  difference  as  sulfur  soluble  in 
CS2. 

Ash. — Weigh  out  2-5  grams  in  a  porcelain  crucible;  ignite, 
gently  at  first,  and  finally  in  a  full  Tirrill  flame.  Cool  the  ash 
in  a  desiccator  and  weigh. 

FUMING  SULFURIC  ACID  (OLEUM) 

General. — Fuming  sulfuric  acid  or  oleum  consists  of  a  solution 
of  SOs  in  cone.  H^SO*.  From  a  determination  of  the  total  SOs, 
the  amount  of  free  SOs  and  of  H2SO4  can  be  calculated.  The 
amount  of  free  SOs  varies  widely — a  common  concentration  is 
18  to  25%,  but  it  may  run  over  60%. 

Total  SOs. — Since  oleum  takes  up  water  very  rapidly,  great 
precautions  must  be  observed  in  getting  the  sample  for  analysis. 
The  most  satisfactory  procedure  is  as  follows:  Seal  off  the  end 
of  an  ordinary  glass  tube  and  blow  a  bulb  about  0.75  inch  in  diam- 

17 


18  TECHNICAL  METHODS  OF  ANALYSIS 

eter.  Draw  the  other  end  out  to  a  capillary.  Cool  and  weigh, 
Warm  the  bulb  end  some  distance  from  the  flame  and  immerse 
the  capillary  in  the  oleum.  With  the  end  still  immersed,  cool  the 
bulb  as  rapidly  as  possible.  The  contraction  of  air  will  draw  the 
oleum  up  into  the  bulb.  Remove  the  bulb,  invert  it,  and  sea] 
off  the  capillary  end  in  a  flame.  Clean  the  outside  of  the  bulb 
carefully  and  again  weigh  to  obtain  the  amount  of  oleum  which  it 
contains.  Great  care  must  be  taken  in  handling  the  bulb,  as  the 
material  in  it  is  very  dangerous. 

Fill  a  500  cc.  glass-stoppered  bottle  about  two-thirds  full  of 
distilled  water  and  add  to  it  sufficient  0.5  N  NaOH,  carefully 
measured,  to  give  a  slight  excess.  If  the  oleum  is  assumed  to 
contain  90%  of  total  SOs,  and  the  corresponding  amount  of  NaOH 
calculated  on  this  basis  from  the  weight  taken,  it  will  give  a  suf- 
ficient excess. 

Immerse  the  bulb  in  this  solution,  hold,  it  firmly  against  the 
bottom  with  a  rubber-tipped  policeman  or  glass  stirring  rod 
and  carefully  break  the  capillary  end.  Stopper  the  bottle  and 
shake.  Finally  the  bulb  itself  should  be  broken  and  also  the  tip 
of  the  capillary  crushed  to  make  sure  that  all  the  acid  has  come  in 
contact  with  alkali.  Add  methyl  orange  and  titrate  the  excess 
of  NaOH  with  0.5  N  or  0.1  N  HC1.  Then  transfer  to  a  500  cc. 
graduated  flask  and  make  up  to  the  mark  with  distilled  water. 
Pipette  100  cc.  into  a  250  cc.  beaker  and  add  5  cc.  of  10%  BaCl2 
solution  diluted  to  about  50  cc.  It  is  important  that  the  latter 
be  added  drop  by  drop  and  that  both  solutions  be  boiling. 

If  possible,  boil  for  five  minutes  and  let  stand  overnight. 
The  next  morning  reheat  the  solution  on  the  steam  bath  and  filter. 
If  results  are  desired  quickly,  boil  the  solution  for  at  least  thirty 
minutes  after  adding  BaCl2,  let  settle  till  clear  and  filter.  Wash 
with  boiling  water,  ignite  in  a  weighed  platinum  crucible,  cool  in 
air,  moisten  with  dilute  H2S04,  again  ignite  (gently  at  first  to  avoid 
spattering),  cool  in  a  desiccator,  and  weigh  as  BaSO*.  Calculate 
tc  SO3. 

CALCULATIONS. — Subtract  from  100%  the  per  cent  of  total 
80s  obtained  by  the  BaS04  method.  The  difference  is  H2O  com- 
bined as  H2SO4.  Calculate  this  to  H2SO4.  Subtract  this  per- 
centage from  100%.  The  difference  is  free  SOs.  Report  as 
follows: 


GENERAL  INORGANIC  ANALYSES  19 

Total  Sulfur  Trioxide,  S03. 
Equivalent  to: 

Sulfuric  Acid,  H2S04. 
Free  Sulfur  Trioxide,  SO3. 

Factors— I  cc.  0.5  N  NaOH  =  0.020015  gram  SO3. 
BaS04X  0.3430  =  SO3. 
H2OX  5.444  =  H2SO4. 

NOTES. — (1 )  The  titration  is  carried  out  merely  as  a  check.  Theoretically 
it  should  give  the  same  amount  of  total  SOs  as  the  precipitation  method,  but 
generally  it  shows  somewhat  higher  results.  If  the  result  for  SO3  by  titra- 
tion varies  widely  from  that  obtained  by  precipitation,  the  latter  should  be 
carefully  checked. 

(2)  On  account  of  the  necessity  of  aliquoting  and  also  on  account  of  the 
large  factor  from  H2O  to  H2SO4,  it  is  necessary  to  work  with  extreme  care  and, 
wherever  possible,  it  is  advisable  to  run  at  least  5  determinations  and  take  the 
average. 

(3)  Oleum  samples   should  always   be  kept    in  glass-stoppered   bottles 
away  from  light. 

(4)  The  freezing  point  of  oleum  depends  upon  the  amount  of  free  SO3 
which  it  contains,  and  analytical  results  can  therefore  be  checked  by  deter- 
mining the  freezing  point. 

ALKALIES 

(HYDROXIDES,  CARBONATES  AND  BICARBONATES  OF  SODIUM 
AND  POTASSIUM) 

General. — Mixtures  of  carbonates  and  bicarbonates  or  of  car- 
bonates and  hydroxides  of  the  alkalies  can  be  analyzed  by  a  double 
titration  with  standard  acid,  using  phenolphthalein  and  methyl 
orange  indicators.  If  only  Na  or  K  is  present,  the  amounts  of 
carbonate  and  hydroxide  can  be  calculated  directly;  otherwise 
the  proportions  of  Na  and  K  must  also  be  determined  on  a  sep- 
arate portion.  (For  the  determination  of  potassium,  see  page  41.) 
The  method  of  double  titration  is  chiefly  of  value  for  mixtures  of 
hydroxide  and  carbonate  containing  only  a  small  proportion  of 
carbonate.  Where  the  proportion  of  carbonate  is  high  it  is 
preferable  to  use  the  barium  chloride  method. 

In  reporting  results,  the  total  alkalinity  calculated  as  Na20 
(or  K2O)  should  be  expressed,  as  well  as  the  various  forms  of 
alkalinity. 

In  the  following  procedures  it  is  assumed  that  the  material 
contains  K  or  Na,  but  not  both,  and  that  it  contains  carbonate, 


20  TECHNICAL  METHODS  OF  ANALYSIS 

bicarbonate,  hydroxide,  carbonate  and  bicarbonate,  or  carbonate 
and  hydroxide.  (It  should  be  noted  that  bicarbonate  cannot  exist 
in  the  presence  of  hydroxide.) 

Moisture. — Weigh  out  as  large  a  sample  as  practicable,  dis- 
solve rapidly  in  CO2-free  water  and  make  up  to  volume.  Pipette 
an  aliquot  representing  1  or  2  grams  into  a  platinum  or  porcelain 
dish.  Evaporate  to  dryness  and  dry  to  constant  weight  at  105°  C. 
Report  loss  as  moisture. 

NOTE. — In  the  case  of  soda  ash  (or  K2CO3),  1-5  grams  of  sample  may  be 
weighed  out  directly  and  dried  to  constant  weight.  In  the  case  of  caustic 
soda  or  potash,  the  moisture  is  generally  taken  "by  difference,"  as  it  is  very 
difficult  to  get  accurate  results  on  account  of  the  tendency  to  carbonate.  If 
bicarbonates  are  present,  the  above  method  cannot  be  used  for  the  moisture 
determination,  as  bicarbonates  will  change  to  carbonates.  In  such  cases 
the  material  should  be  heated  for  at  least  two  hours  at  200°  C.  and  the  loss 
reported  as  moisture  plus  half-bound  carbon  dioxide. 

DETERMINATION  OF  THE  ALKALIES 

Qualitative  Tests. — To  test  for  hydroxide,  dissolve  a  small 
amount  of  the  sample  in  CCVfree  water,  add  an  excess  of  BaCl2 
solution  and  filter  rapidly.  If  the  filtrate  is  alkaline  to  phenol- 
phthalein,  hydroxide  is  present.  More  BaCl2  solution,  however, 
should  be  added  to  the  filtrate  to  make  sure  that  an  excess  has 
been  used.  Carbonate  or  bicarbonate  is,  of  course,  indicated  by 
effervescence  with  acid.  If  hydroxide  is  present,  the  material  is 
free  from  bicarbonates.  If  hydroxide  is  not  present,  the  presence 
of  bicarbonate  would  be  indicated  in  the  quantitative  analysis 
by  the  fact  that  the  titration  with  methyl  orange  would  be  more 
than  twice  that  with  phenolphthalein. 

Sodium  (or  Potassium)  Carbonate  and  Bicarbonate. — Dissolve 
a  considerable  amount  of  the  sample  in  freshly  boiled  distilled 
water  and  titrate  an  aliquot  of  the  solution  corresponding  to  1  gram 
(or  more  if  necessary)  directly  with  0.5  N  acid,  and  phenolphtha- 
lein; then  add  methyl  orange  and  complete  the  titration  as 
described  below  under  Caustic  Soda.  If  the  phenolphthalein 
titration  is  one-half  the  total  methyl  orange  titration,  carbonates 
only  are  present. 

In  case  bicarbonates  are  present,  twice  the  phenolphthalein 
titration  will  give  normal  carbonates,  and  the  difference  between 
the  methyl  orange  titration  and  twice  the  phenolphthalein  titra- 


GENERAL  INORGANIC  ANALYSES  21 

tion  will  give  bicarbonate.  In  case  carbonate  alone  is  present, 
calculate  the  methyl  orange  titration  direct,  both  as  carbonate  and 
as  Na2O  or  K2O.  In  making  calculations  use  the  following  factors: 
CALCULATION.— 1  cc.  0.5  N  acid  =  0.02001  gram  NaOH. 

=  0.02806  gram  KOH. 

=  0.02650  gram  Na2C03. 

=  0.03455  gram  K2CO3. 

=  0.02355  gram  K2O. 

=  0.01550  gram  Na2O. 

NOTES. — (1).  The  above  method  is  reliable  only  for  comparatively  small 
amounts  of  carbonate  in  the  presence  of  caustic.  For  small  amounts  of  caustic 
in  the  presence  of  carbonate,  results  are  only  approximate. 

(2)  In  carrying  out  the  titration  it  is  essential  to  have  sufficient  water  so 
that  no  bubbles  of  CO2  are  given  off  during  the  phenolphthalein  titration. 
The  acid  should  also  be  added  slowly  with  stirring.     To  obtain  reliable  results 
all  precautions  and  directions  must  be  exactly  observed. 

(3)  For  the  so-called  "New  York-Liverpool  Test"    multiply  the  actual 
per  cent  of  Na-jO  found  by  1.03226  and  for  the  "Newcastle  Test"  multiply 
the  actual  per  cent  of  Na^O  by  1.013. 

Caustic  Soda  (or  Caustic  Potash). — Caustic  soda  and  potash 
invariably  contain  a  certain  amount  of  carbonate.  Carbonate 
and  hydroxide  can  both  be  determined  in  one  operation  as  follows: 
Dissolve  a  considerable  amount  of  the  sample  in  freshly  boiled 
distilled  water  and  dilute  to  volume,  working  rapidly  and  avoiding 
undue  exposure,  as  caustic  rapidly  takes  up  moisture  and  CO2. 

Pipette  an  aliquot  of  the  solution  corresponding  to  about  1 
gram  into  a  500  cc.  beaker,  dilute  to  about  450  cc.,  add  1  cc.  of 
phenolphthalein  solution,  and  with  the  tip  of  the  burette  beneath 
the  surface  of  the  solution,  titrate  with  0.5  N  acid  until  the  pink 
color  just  disappears.  Then  add  3  or  4  drops  of  methyl  orange 
indicator  and  continue  the  titration  to  the  first  beginning  of  a 
permanent  pink  color.  The  first  titration  gives  the  number  of 
cc.  of  acid  required  to  neutralize  all  the  hydroxide  and  half  of 
the  carbonate,  since  phenolphthalein  is  neutral  to  bicarbonate. 
The  methyl  orange  (total)  titration  gives  the  total  alkalinity. 

Let  X  =  cc.  required  with  phenolphthalein, 
and         y  =  cc.  required  with  methyl  orange; 
then        2(y—x)  =  cc.  due  to  carbonate, 
and         y—2(y—x)   or   2x—y  =  cc.  due  to  hydroxide. 


22  TECHNICAL  METHODS  OF  ANALYSIS 

Sodium  or  Potassium  Carbonate  and  Bicarbonate. — Dissolve 
a  considerable  amount  of  the  sample  in  freshly  boiled  distilled 
water  and  make  up  to  volume.  Test  a  small  portion  for  the  pres- 
ence of  hydroxide  by  treating  with  BaCb  as  previously  described. 

(A)  TOTAL  ALKALI. — Pipette  out  an  aliquot  corresponding  to 
1  gram,  or  more  if  necessary,  into  a  500  cc.  beaker.    Add  3  drops  of 
methyl  orange  and  titrate  rapidly  to  the  end  point.     This  is  merely 
a  preliminary  titration.     Then  take  another  aliquot  and  add  1  cc. 
less  of  0.5  N  acid  than  required  by  the  first  titration,  taking  care 
not  to  lose  any  liquid  by  effervescence.     Cover  the  beaker  with  a 
watch  glass,  boil  off  the  liberated  CO2,  cool,  add  2  drops  of  methyl 
orange  and  titrate  to  the  exact  end  point.     In  this  titration,  stir 
well  when  approaching  the  end  point  and  add  the  acid  a  drop  at  a 
time  so  that  the  color  change  will  be  sharp. 

(B)  CAUSTIC   ALKALI. — If  the   sample   contains    hydroxide, 
pipette   an    aliquot   corresponding   to    1    gram   into   a   250    cc. 
beaker  and  add  100  cc.  of  10%  BaCl2  solution.    Stir  thoroughly, 
add  5  drops  of  phenol phthalein  indicator  and  titrate  cold  with  0.5 
N  acid.     Calculate  the  titration  to  NaOH  or  KOH. 

NOTE. — If  the  sample  contains  hydroxide  it  cannot  contain  bicarbonate. 
In  this  case  subtract  the  titration  required  by  the  hydroxide  from  the  titra- 
tion of  total  alkali  and  calculate  the  difference  to  carbonate. 

(C)  BICARBONATE. — Pipette    an   aliquot   corresponding   to    1 
gram  into  a  250  cc.  beaker  and  titrate  with  0.5  N  NaOH  solution 
until  a  drop  of  the  solution  added  to  a  drop  of  AgNO3  indicator 
(10%  solution)  on  a  spot  plate  gives  a  dark  coloration  at  once. 
Calculate  the  titration  to  bicarbonate. 

CALCULATION.— 1  cc.  of  0.5  N  caustic  =  0.04201  gram  NaHCO3. 

=  0.05006  gram  KHCO3. 

NOTE. — To  obtain  the  true  carbonate,  subtract  the  titration  required  by 
bicarbonate  from  the  titration  for  total  alkalinity  and  calculate  the  difference 
to  carbonate. 

Impurities. — The  impurities  generally  encountered  in  alkalies 
are  chlorides,  sulfates,  and  iron  and  alumina.  These  are  deter- 
mined in  the  usual  way.  Before  precipitating  the  sulfate,  the 
solution  should  be  boiled  after  adding  HC1,  in  order  to  remove 
excess  CO2.  Iron  is  best  determined  colorimetrically. 


GENERAL  INORGANIC  ANALYSES  '  23 


AMMONIUM  HYDROXIDE 

General. — Aqua  ammonia  (U.  S.  P.)  is  a  solution  containing 
10%  by  weight  of  NHs.  Stronger  aqua  ammonia  (U.  S.  P.) 
contains  28%  by  weight  of  NHs.  The  latter  is  about  the  strength 
of  the  cone,  ammonium  hydroxide  of  commerce.  The  crude 
ammonia  liquor  of  the  gas  works  contains  generally  between  1.25% 
and  2%  of  NHs  and  is  generally  concentrated  to  15-17%  for 
shipment. 

As  ammonia  is  very  volatile,  the  sample  should  be  analyzed 
as  quickly  as  possible  after  receipt  and  kept  tightly  stoppered  at 
all  times. 

Specific  Gravity. — Determine  the  sp.  gr.  with  a  hydrometer  or 
the  Westphal  balance  at  15.5°  C.  For  accurate  work  the  temper- 
ature should  be  adjusted  within  a  degree  or  so.  For  ordinary 
commercial  purposes,  however,  the  sp.  gr.  may  be  taken  at  room 
temperature  and  corrected  to  15.5°  C.  by  means  of  standard 
ammonia  tables.  As  the  coefficient  varies  with  different  tempera- 
tures, the  correction  cannot  be  made  by  formula. 

Ammonia,  NH3. — (A)  REFINED  AMMONIA  WATER. — For  strong 
'liquors,  pipette  25  cc.  into  a  weighing  bottle,  stopper  tightly  and 
weigh.  Then  using  the  same  pipette  and  allowing  it  to  drain 
for  the  same  length  of  time,  pipette  another  25  cc.  into  a  250 
cc.  graduated  flask  two-thirds  filled  with  water.  Hold  the  tip 
of  the  pipette  very  near  the  surface  of  the  water.  Make  up  to 
the  mark  and  mix  thoroughly.  Titrate  25  cc.  of  this  with  0.5  N 
HC1,  using  methyl  red  or  methyl  orange  indicator  [see  page  66, 
note  (3)].  From  the  weight  of  sample  taken  and  the  titration, 
calculate  the  per  cent  of  NHs  by  weight. 

CALCULATION.— 1  cc.  of  0.5  N  HC1  =  0.008516  gram  NH3- 

=  0.017524  gram  NH4OH. 

NOTE. — The  above  proportions  are  for  cone,  ammonia  water.  For  weaker 
samples  correspondingly  larger  aliquots  should  be  taken  for  analysis. 

(B)  CRUDE  AMMONIA  LIQUOR. — Crude  ammonia  liquor  from 
gas  works  contains  ammonium  sulfate  and  other  salts  as  well  as  free 
NHs,  and  in  such  samples  the  total  ammonia  should  be  determined. 

For  concentrated  liquors,  dilute  25  cc.  to  250  cc.  exactly  as 
described  under  Refined  Ammonia  Water.  Then  pipette  25  cc.  of 


24  TECHNICAL  METHODS  OF  ANALYSIS 

this  solution  into  a  round-bottom  flask  which  can  be  connected 
to  a  condenser  through  a  spray  trap.  This  flask  should  contain 
about  100-150  cc.  of  distilled  water.  Add  a  few  grains  of  gran- 
ulated zinc  or  small  pieces  of  pumice  and  about  5  grams  of  NaOH. 
Connect  to  the  condenser  and  distill  into  50  cc.  of  0.5  N  HC1, 
to  which  has  been  added  a  drop  or  two  of  methyl  orange  or  methyl 
red  (see  page  65).  The  lower  end  of  the  condenser  should  be  con- 
nected to  an  adaptor  which  dips  below  the  surface  of  the  acid. 
Continue  the  distillation  until  about  100  cc.  of  liquid  have  come 
over.  If  the  indicator  in  the  0.5  N  acid  should  lose  its  pink  color, 
add  25  cc.  more  of  0.5  N  acid  immediately.  In  such  case,  the  dis- 
tillation should  also  be  repeated,  distilling  into  a  larger  amount 
of  acid  to  make  sure  that  no  NHa  was  lost.  Titrate  the  excess  of 
0.5  N  acid  with  0.5  N  or  0.1  N  caustic  and  calculate  the  difference 
to  NHs,  as  previously  described. 

NOTE. — The  above  procedure  is  for  concentrated  liquors.  For  the  weak 
liquors  it  is  not  necessary  to  make  up  to  volume,  but  25  or  50  cc.  may  be  dis- 
tilled directly  after  adding  caustic.  For  the  very  weak  waste  liquors,  at  leas'j 
100  cc.  of  the  sample  should  be  taken  for  each  distillation.  The  latter  should 
show  only  a  few  hundredths  of  1%  of  NH3  when  the  concentrating  still  is 
running  efficiently. 


TABLE  SALT 

General. — The  U.  S.  standard  for  table  or  dairy  salt  requires 
that  it  shall  contain  on  the  water-free  basis  not  more  than  the 
following  amounts  of  impurities: 

1.4%  Calcium  Sulfate 

0.5%  Calcium  and  Magnesium  Chlorides 

0.1%  Insoluble  in  Water 

0.05%  Barium  Chloride 

In  addition  to  these  substances,  table  salt  sometimes  contains 
small  amounts  of  calcium  phosphate  and  sodium  and  magnesium 
sulfates.  Natural  salt  also  may  contain  small  amounts  of  sodium 
carbonate,  potassium  chloride  and  other  impurities. 

Appearance. — Examine  the  material  under  the  microscope  and 
note  its  general  appearance.  It  should  be  homogenous  and  free 


GENERAL  INORGANIC  ANALYSES  25 

from  foreign  matter.  Add  a  drop  of  dilute  HC1  to  the  salt  on  the 
slide  and  note  if  there  is  any  effervescence  (€62) . 

Solubility  and  Reaction. — Make  a  nearly  saturated  solution 
with  distilled  \vater.  Test  with  sensitive  litmus  paper.  A  tur- 
bidity which  dissolves  on  the  addition  of  acid  indicates  calcium 
phosphate  or  carbonate. 

Moisture. — Dry  5-10  grams  to  constant  weight  at  105°  C. 
(Three  or  four  hours'  heating  is  generally  sufficient.) 

Phosphoric  Anhydride. — Dissolve  50  grams  in  distilled  water, 
dilute  to  500  cc.  and  pipette  out  100  cc.  (equivalent  to  10  grams). 
Add  10  cc.  of  cone.  HNOa,  then  add  NH4OH  until  the  acid  is 
nearly,  but  not  completely,  neutralized.  Add  an  excess  of  ammo- 
nium molybdate  solution,  warm  gently  and  let  stand  one  hour.  If 
phosphate  is  present,  a  yellow  precipitate  will  form.  If  the  solu- 
tion is  colored  bright  yellow  but  does  not  give  a  precipitate, 
report  a  trace  of  phosphate.  Filter  any  appreciable  precipitate 
and  wash  with  5%  NELiNOa  solution.  This  precipitate  may  be 
filtered  on  a  weighed  filter  paper  and  after  washing  out  the 
NH4NOs  with  a  little  cold  water,  dried  in  a  weighing  bottle  at 
105°  C.  and  weighed  as  ammonium  phosphomolybdate. 

CALCULATION.— (NH4)2HPO4  •  12MoO3  X  0.038  =  P2O5. 

If  preferred,  dissolve  the  yellow  precipitate  in  NELiOH,  add 
an  excess  of  5%  H2SO4,  run  through  a  Jones  reductor  (see  page 
148)  and  titrate  the  Mo  with  0.1  N  KMnO4. 

CALCULATION.— 1  cc.  0.1  N  KMnO4  =  0.000203  gram  P2O5. 

NOTE. — Both  of  the  above  methods  for  P2O5  are  dependable  only  for 
the  determination  of  small  amounts. 

Iron  Oxide  and  Alumina. — (a)  In  the  absence  of  P20 5. — To  100 
cc.  of  the  above  solution  (equivalent  to  10  grams)  add  a  few 
drops  of  cone.  HNOa  and  boil  to  oxidize  Fe.  Then  add  a  slight 
excess  of  NlrLiOH,  boil  until  the  odor  has  nearly  disappeared, 
filter,  wash  with  hot  water,  ignite  in  a  blast  lamp  and  weigh  as 
Fe203+Al2O3. 

(b)  In  the  presence  of  P20s. — To  100  cc.  of  the  original  solution, 
add  slightly  more  than  enough  Fe2Os  to  combine  with  the  P2C>5. 
This  should  be  calculated  from  the  amount  of  P2Os  found.  To 
determine  the  correct  amount,  proceed  as  follows: 

Weigh  out  1  gram  of  ferrous  ammonium  sulfate,  dissolve  in  a 


26  TECHNICAL  METHODS  OF  ANALYSIS 

little  water,  boil  with  a  few  drops  of  cone.  HNO3,  make  up  to 
100  cc.  and  use  the  proper  aliquot  as  calculated  from  the  following 
approximate  factors: 


P2O5Xl.l2  = 

Fe2C>3  X  5  =  Ferrous  ammonium  sulfate. 

Ferrous  ammonium  sulfate  X  0.2036  =  Fe203. 

After  adding  the  iron  solution,  add  a  slight  excess  of  NILiOH 
and  boil  until  the  odor  is  nearly  gone.  This  precipitates 
all  the  P2O5  as  FePO4  and  the  excess  of  Fe  as  Fe(OH)3.  Filter, 
wash,  ignite,  blast  and  weigh  as  Fe203-f-Al203+P205.  From  this 
weight  subtract  the  amount  of  P20s  previously  determined  and  the 
weight  of  Fe203  added.  The  remainder  will  be  the  Fe2O3H-Al203 
in  the  salt. 

Total  Lime.  —  In  the  filtrate  from  the  Fe20s  all  the  Ca  is 
present  as  CaCl2.  Heat  to  boiling,  add  a  slight  excess  of 
ammonium  oxalate  and  let  stand  until  clear  (several  hours  if 
possible).  Filter,  ignite  (finally  with  a  blast  lamp)  in  a  platinum 
crucible  and  weigh  as  CaO. 

NOTE.—  The  CaC2O4  may  also  be  titrated  directly  with  O.I  N  KMnO4  in 
the  usual  way  (see  page  326). 

Magnesia.  —  Concentrate  the  filtrate  from  the  .  CaC2O4  until 
crystals  begin  to  form.  Then  add  a  little  water  to  dissolve 
the  crystals,  and  finally  add  a  large  excess  of  ammonium  or  sodium 
phosphate  and  cone.  NE^OH.  Let  stand  overnight.  Filter  on  a 
weighed  Gooch  crucible  and  wash  with  dilute  NKUOH;  ignite, 
first  gently  and  then  strongly,  until  white  or  light  gray,  and 
weigh  as  Mg2P20?.  Calculate  to  MgO. 

CALCULATION.—  Mg2P2O7X  0.3621  =  MgO. 

Sulfur  Trioxide.  —  To  100  cc.  of  the  original  solution  (equivalent 
to  10  grams)  add  5  cc.  of  dil.  HC1  and  heat  to  boiling.  Then  add  5 
cc.  of  10%  BaCl2  solution  diluted  to  100  cc.  This  should  be 
added  boiling  hot,  drop  by  drop.  Let  stand  overnight.  Filter 
while  hot  and  wash  thoroughly  with  hot  water.  Ignite  in  a 
platinum  crucible  and  weigh  as  BaSC>4.  Calculate  to  863. 

CALCULATION.—  BaSO4  X  0.3430  =  SO3. 

Barium.  —  If  80s  was  found,  Ba  cannot  be  present  in  the  solu- 
tion but  might  be  present  in  the  insoluble  portion.  If  SOs  was 


GENERAL  INORGANIC  ANALYSES  27 

not  found,  test  for  Ba  by  adding  5  cc.  of  dil.  H^SO*  to  100  cc.  of  the 
original  solution.  Heat  to  boiling  and  let  stand  several  hours, 
preferably  overnight.  Filter  hot,  wash  with  hot  water,  ignite  in 
a  platinum  crucible  and  weigh  as  BaSO4.  Calculate  to  BaCk. 

CALCULATION.— BaSO4  X  0.8923  =  BaCl2. 

Salt. — Dilute  100  cc.  of  the  original  solution  to  500  cc. 
Thoroughly  mix  and  pipette  out  25  cc.  of  this  solution,  equivalent 
to  0.5  gram  of  the  sample.  Dilute  to  about  250  cc.,  add  5  cc.  of 
dil.  HNOa  and  precipitate  with  an  excess  of  AgNOa  solution  in  a 
large  glass-stoppered  Erlenmeyer  flask.  Shake  violently,  let 
stand  at  least  one  hour,  filter  on  a  weighed  Gooch  crucible,  wash 
with  water  containing  a  few  drops  of  AgNOa  solution  and  finally 
once  with  boiling  distilled  water.  Dry  at  105°  C.  Place  the 
Gooch  crucible  in  a  large  platinum  crucible,  and  heat  gently  until 
the  edges  of  the  AgCl  just  begin  to  fuse.  Cool  in  a  desiccator  and 
weigh.  Calculate  to  NaCl. 

CALCULATION.— AgCl  X  0.4078  =  NaCl. 

Potash. — Determination  of  potash  is  seldom  necessary.  If 
desired,  proceed  according  to  directions  on  page  41. 

Calculations. — Calculate  SOa  to  CaSO4.  If  there  is  an 
excess  of  SOa,  calculate  this  to  MgSC>4,  and  if  still  an  excess,  to 
Na2SO4.  If  CaO  is  in  excess  of  SOa,  calculate  the  excess  to  CaCOa 
(if  the  salt  solution  is  turbid  and  shows  presence  of  carbonates) 
or  to  CaO  (if  the  salt  solution  is  alkaline)  or  to  CaCU  (if  the  solu- 
tion is  clear  and  neutral). 

All  ?2Os  must  first  be  calculated  to  Caa(PO4)2,  and  any 
excess  over  CaO  to  Mga(P04)2,  and  any  further  excess  to 
Na2HP04.  Any  excess  of  MgO  over  SOa  or  P20s  calculate  to 
MgCOa,  MgO  or  MgCl2  (under  the  same  conditions  as  for  CaO) . 
Report  Fe2Oa  and  A^Oa  as  such. 

If  any  BaCb,  CaCU  or  MgCl2  is  present, subtract  the  equivalent 
amount  of  AgCl  from  the  total  AgCl  before  calculating  the  latter 
to  NaCl. 

If  any  potash  is  present,  calculate  it  to  KC1  and  subtract  the 
equivalent  amount  from  the  NaCl. 

NOTE. — If  the  amount  of  iron  is  desired,  it  is  best  determined  colorimet- 
rically  as  in  water  analysis.  (See  page  513.) 


28  TECHNICAL  METHODS  OF  ANALYSIS 


SODIUM  NITRITE 

Determination  of  NaNC>2. — Weigh  out  on  a  balanced  watch 
glass  exactly  4  grams  of  the  sample  and  dissolve  in  water.  Filter, 
if  the  solution  contains  much  suspended  matter.  Dilute  to  1  liter 
in  a  volumetric  flask. 

Into  a  clean  Erlenmeyer  flask  of  300-400  cc.  capacity  pipette 
50  cc.  of  0.1  N  KMnO4  solution  and  dilute  with  150  cc.  of  water. 
Pipette  into  this  25  cc.  of  the  nitrite  solution  to  be  analyzed,  equiva- 
lent to  0.1  gram  of  the  original  sample.  Heat  just  to  boiling. 
Add  20  cc.  of  dil.  H2S04  and  let  stand  ten  minutes.  Cool  under 
the  tap.  Add  30  cc.  of  10%  KI  solution.  Upon  adding  the 
H2SO4  there  will  be  a  heavy  precipitate  of  Mn02,  but  the  KI 
solution  will  dissolve  this  and  should  give  a  perfectly  clear,  brown- 
ish red  solution.  Titrate  this  with  0.1  N  thiosulfate,  adding 
about'  5  cc.  of  starch  solution  when  the  color  begins  to  get  pale. 

Run  a  "  blank  "  with  50  cc.  of  the  0.1  N  KMn04  solution, 
going  through  all  the  operations  except  the  addition  of  the  nitrite 
solution,  and  subtract  the  blank  from  the  titration  of  the  sample. 
Calculate  the  difference  to  NaNC>2. 

CALCULATION.— 1  cc.  0.1  N  Na2S2O3  =  0.003451  gram  NaNO2. 

NOTE. — After  adding  the  H2SO4  to  the  hot  solution,  the  liquid  should  be 
distinctly  pink  or  magenta  after  allowing  the  precipitate  to  settle.  If  it  is  not, 
too  little  KMnO4  has  been  used,  and  the  analysis  must  be  repeated  with  a 
larger  excess. 


SODIUM  SULFIDE 

General. — Sodium  sulfide  occurs  commercially  in  two  forms — 

(1)  crystals,  Na2S-9H2O,  containing  theoretically  13.35%  S  and 

(2)  fused  sodium  sulfide,  Na2$,  containing  theoretically  41.07%  S. 
As  a  matter  of  fact,  the  crystals  often  contain  more  than  the 
theoretical  amount  of  S,  due  to  loss  of  moisture ;  and  the  fused 
material  is  seldom   completely  dehydrated  and  usually  contains 
about  25%  S  or  62%  Na2S. 

Sulfide-sulfur. — Dissolve  10  grams  of  the  material  in  water 
and  make  up  to  500  cc.  Pipette  out  25  cc.  and  add  to  this  50  cc. 
of  0.1  N  iodine  (more  if  necessary).  Titrate  back  the  excess  of 


GENERAL  INORGANIC  ANALYSES  29 

iodine  with  0.1   N  thiosulfate.     The  iodine  precipitates  sulfur 
according  to  the  reaction  — 


Calculate  the  percentages  of  S  and  of  Na^S. 
CALCULATIONS.  —  1  cc.  0.1  N  iodine  =  0.001603  gram  S. 

=  0.003903  gram  Na2S. 

NOTE.  —  This  determination  is  the  only  determination  generally  necessary. 
If  it  is  desired  to  determine  iron,  dissolve  5  grams,  acidify  with  HC1,  boil  off 
H2S,  add  a  few  drops  of  HNO3  and  continue  boiling.  Filter,  precipitate  iron 
in  the  filtrate  with  NH4OH,  dissolve  in  hot  5%  H2SO4,  pass  through  a  Jones 
reductor  (see  page  138)  and  titrate  with  standard  permanganate  (or 
determine  colorimetrically  in  the  usual  manner). 


SODIUM  SILICATE  (WATER  GLASS) 

General. — Anhydrous  water  glass  is  generally  given  the  formula 
,  containing  20.45%  of  Na2O.  According  to  the  method 
of  manufacture,  however,  its  actual  composition  varies  consider- 
ably from  this  and  in  commerce  it  is  furnished  as  a  thick  solution, 
generally  of  a  gravity  either  40°,  50°,  or  60°  Baume.  When  exposed 
to  the  air,  it  sets  first  to  a  stiff  jelly  and  then  to  a  hard  mass. 

Specific  Gravity. — If  the  solution  is  thin  enough,  determine  the 
sp.  gr.  with  a  hydrometer.  Otherwise  fill  a  graduated  flask  to  the 
mark  with  the  solution  and  compare  its  weight  with  an  equal  vol- 
ume of  water  at  the  same  temperature. 

Moisture. — Moisture  is  not  completely  given  off  at  105°  C. 
To  get  accurate  results  the  material  must  be  ignited. 

Weigh  accurately  about  10  grams  in  a  beaker.  Dilute  with 
water,  transfer  to  a  500  cc.  volumetric  flask  and  make  up  to  the 
mark.  Mix  thoroughly  and  pipette  50  cc.  into  a  weighed  platinum 
dish.  Dry  in  the  oven  at  105°  C.  and  finally  ignite  cautiously  to 
avoid  spattering.  Subtract  the  weight  of  residue  from  the 
weight  of  the  aliquot  taken  and  calculate  the  per  cent  loss  on 
ignition.  Report  as  moisture. 

Silica. — Place  another  aliquot  of  50  cc.  of  the  solution  in  a 
platinum  dish,  dilute  to  about  100  cc.,  add  slowly  5  cc.  of  cone. 
HC1  and  evaporate  to  dryness.  Heat  at  135°  C.  for  two  hours, 
add  a  little  cone.  HC1  and  then  5  cc.  of  water.  Warm  a  few 


30  TECHNICAL  METHODS  OF  ANALYSIS 

moments,  filter  and  wash  with  hot  water.  Evaporate  the  filtrate 
to  dryness  and  heat  as  before  for  0.5  hour.  Take  up  with  cone. 
HC1  and  water  and  filter.  Combine  both  silica  residues  in  a 
weighed  platinum  crucible,  dry  in  the  oven,  then  ignite  intensely 
with  a  blast  lamp,  cool  in  desiccator,  and  weigh.  .  Report  the 
result  as  total  SiO2. 

NOTE. — From  the  above  figure  the  amount  of  sodium  silicate  can  be 
approximately  calculated  as  follows:  SiC>2 X  1.257  =  Na2Si4Og. 

Sodium  Oxide. — The  Na20  alkalinity  can  be  determined  by 
titrating  with  0.1  N  acid  and  phenolphthalein.  Take  an  aliquot 
of  50  cc.,  corresponding  to  1  gram,  dilute  to  500  cc.  with  water  free 
from  CO2  and  titrate  until  the  pink  color  of  the  phenolphthalein 
just  disappears.  Calculate  to  Na20. 

CALCULATION.— 1  cc.  0.1  N  acid  =  0.003100  gram  Na2O. 

(2)  The  total  Na2O,  which  will  include  the  sodium  of  impurities, 
such  as  sodium  chloride  and  sulfate,  is  determined  as  follows: 

Combine  the  filtrates  from  the  SiC>2  determination,  add  a  slight 
excess  of  NELiOH,  and  boil.  Then  add  a  few  cc.  of  ammonium 
carbonate  solution  and  digest  for  some  time.  If  any  precipitate 
forms,  filter  it  off.  Make  the  filtrate  slightly  acid  with  H^SCU 
and  evaporate  to  dryness  in  a  weighed  platinum  dish.  Ignite 
until  no  more  white  fumes  are  given  off.  Saturate  with  water,  add 
a  few  drops  of  ammonium  carbonate  solution,  evaporate  to  dry- 
ness,  again  ignite  and  weigh  as  Na2SC>4.  Calculate  the  total  Na2O. 

CALCULATION.— Na2S04  X  0.4364  =  Na2O. 

Sodium  Sulfate  and  Chloride. — If  it  is  desired  to  determine 
these  impurities,  proceed  in  the  usual  way,  using  a  very  dilute  solu- 
tion. Make  the  solution  acid  in  the  cold,  adding  dil.  acid  a  little 
at  a  time.  If  cone,  acid  or  heat  is  applied,  the  silicic  acid  will 
precipitate.  In  determining  sulfate,  the  solution  may  be  heated 
after  it  has  been  made  acid,  if  it  is  sufficiently  dilute. 

POTASSIUM  OR  SODIUM  BICHROMATE 

Potassium  Bichromate. — Dissolve  8-9  grams  of  the  sample, 
accurately  weighed,  in  distilled  water  and  dilute  to  1  liter.  Pipette 
25  cc.  of  this  solution  into  a  wide-mouth,  glass-stoppered  bottle; 
add  15  cc.  of  a  10%  KI  solution  and  then  7  CQ,  of  cone.  HC1. 


GENERAL  INORGANIC  ANALYSES  31 

Run  in  from  a  burette  0.1  N  sodium  thiosulfate  until  the  brown 
color  is  nearly  gone.  Then  add  a  few  drops  of  starch  solution  and 
complete  the  titration  carefully  until  the  color  just  changes  from 
dark  blue  to  light  green. 

CALCULATION.— 1  cc.  0.1  N  Na2S203  =  0.004903  gram  K2Cr207. 

Sodium  Bichromate. — The  same  procedure  may  be  used  for 
the  analysis  of  sodium  bichromate,  using  the  following  factors  for 
calculation : 

1  cc.  0.1  N  Na2S203  =  0.004367  gram  Na2Cr2O7. 

=  0.004967  gram  Na2Cr2O7-2H2O. 


CYANIDES  OF  POTASSIUM  AND  SODIUM 

General. — There  is  very  little  pure  potassium  cyanide  on  the 
market  to-day.  Most  material  so  labeled  contains  varying 
amounts  of  sodium  cyanide.  As  an  insecticide  or  poison,  however, 
it  is  chiefly  bought  and  sold  on  the  cyanogen  content. 

The  following  procedures  are  the  official  methods  of  the  Asso- 
ciation of  Official  Agricultural  Chemists: 

CAUTION. — Cyanides  are  extremely  dangerous  poisons.  They  should  not 
be  handled  with  the  hands:  and  if  necessary  to  grind  them,  a  mask  should 
be  worn,  to  prevent  inhaling  the  fine  particles.  On  no  account  add  a  strong 
acid  to  a  solution  of  a  cyanide. 

Cyanogen. — Weigh  about  10  grams  of  the  sample  in  a  weigh- 
ing bottle,  dissolve  in  water,  and  make  up  to  volume  in  a  liter 
graduated  flask.  Pipette  a  100  cc.  aliquot  and  titrate  it  with  0.1  N 
AgN03,  drop  by  drop,  stirring  constantly,  until  1  drop  produces  a 
permanent  turbidity.  In  calculating  the  results,  1  equivalent  of 
silver  is  equal  to  2  equivalents  of  cyanogen,  according  to  the  fol- 
lowing equation: 

2NaCN+ AgNO3  =  NaCNAgCN+NaNO3. 

Reserve  the  titrated  solution  for  the  determination  of  chlorine. 
CALCULATIONS.— 1  cc.  of  0.1  N  AgNO3  =  0.005203  gram  CN. 

=  0.009802  gram  NaCN. 
=  0.01302  gram  KCN. 


32  TECHNICAL  METHODS  OF  ANALYSIS 

Chlorine. — After  completion  of  the  titration  for  cyanogen,  as 
directed  above,  add  a  few  cc.  of  10%  K2CrO4  solution  as  indicator 
and  continue  the  titration  with  0.1  N  AgNOs  to  the  appearance 
of  the  red-brown  color  of  Ag2Cr04. 

The  first  titration  with  AgNOs  represents  the  cyanogen  present 
according  to  the  above  equation.  The  second  titration  represents 
the  cyanogen  and  chlorine  according  to  the  following  equation : 

NaCNAgCN+NaCl+2AgNO3  =  2NaNO3+2AgCN+ AgCl. 

Therefore,  subtract  the  first  reading  of  the  burette  from  the 
final  reading  and  calculate  the  difference  to  chlorine. 

CALCULATION.— 1  cc.  of  0.1  N  AgN03  =  0.003546  gram  Cl. 

=  0.005846  gram  NaCl. 

=  0.007456  gram  KC1. 

REFERENCE. — J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis 
(1916),  page  72. 


ACETATE  OF  LIME 

General. — Commercial  gray  acetate  of  lime  is  the  crude  product 
from  which  acetic  acid  is  obtained.  In  the  distillation  of  wood,  a 
mixture  of  acetic  acid,  wood  alcohol,  tar,  etc.,  is  obtained.  The 
acetic  acid  and  alcohol  are  separated  by  distillation  from  the  tar. 
This  mixture  is  neutralized  with  lime  and  the  alcohol  distilled  off, 
leaving  acetate  of  lime. 

The  only  determinations  which  are  usually  necessary  are  the 
amounts  of  mois'ture  and  of  true  acetate  of  lime.  A  good  grade  of 
acetate  should  contain  not  more  than  5%  of  moisture  and  should 
show  at  least  80%  of  acetate  of  lime  when  analyzed  by  the  fol- 
lowing procedure. 

Moisture. — Dry  5-10  grams  at  100°  C.  for  two  hours.  This 
is  generally  sufficient  to  drive  off  all  the  moisture,  but  to  make 
certain  of  this,  after  cooling  in  a  desiccator  and  weighing,  return 
it  to  the  oven  for  another  half  hour  and  again  weigh.  Report 
the  total  loss  as  moisture. 

Acetate  of  Lime. — Determine  the  amount  of  acetic  acid  by 
distillation  and  calculate  it  to  calcium  acetate.  The  apparatus 
is  shown  in  Fig.  1.  Weigh  accurately  2  grams  of  the  sample  into 


GENERAL  INORGANIC  ANALYSES 


33 


the  long-necked,  250  cc.  Kjeldahl  flask  A.  Add  25  cc.  of  water 
and  connect  the  flask  by  a  2-hole  cork  with  the  water  reservoir 
(separatory  funnel)  E  and  the  condenser  F.  Add  to  the  flask  15 
cc.  of  cone,  phosphoric  acid  solution,  sp.  gr.  1.7.  Boil  the  con- 
tents of  flask  A  over  a  Rose  burner  until  the  contents  are  about 
20  cc.  The  acetic  acid  and  steam  will  be  condensed  and  caught  in 
the  receiver  G,  to  which  has  been  added  30  cc.  of  0.5  N  NaOH 
solution. 


FIG.  1. — Apparatus  for  Analysis  of  Acetate  of  Lime, 


Regulate  the  stop  cock  M  so  that  the  water  will  enter  drop  by 
drop  into  the  flask  A,  keeping  the  contents  at  about  20  cc.  Con- 
tinue the  distillation  for  two  hours;  remove  the  receiver  G,  replac- 
ing it  with  a  fresh  receiver,  and  titrate  with  0.5  N  NaOH  and  phe- 
nolphthalein.  At  the  end  of  fifteen  minutes,  titrate  the  amount 
of  acid  in  the  second  receiver,  if  any.  Continue  the  distillation 
until  no  more  acetic  acid  comes  over.  From  the  total  amount  of 


34  TECHNICAL  METHODS  OF  ANALYSIS 

0.5  N  NaOH  neutralized,  calculate  the  amounts  of  acetic  acid  and 
of  calcium  acetate. 

CALCULATION.— 1  cc.  0.5  N  caustic  =  0.03002  gram  HC2H3O2. 

=  0.03954  gram  Ca(C2H3O2)2. 

NOTE. — Make  a  careful  "blank"  with  all  reagents  and  correct  for  any 
acid  obtained.  This  is  very  important  and  must  not  be  neglected. 

REFERENCE. — The  above  method  was  furnished  by  Still  well  and  Gladding, 
New  York,  in  1909  and  has  given  good  results  in  this  laboratory. 


ANTIMONY  SULFIDE 

General. — The  impure  antimony  pentasulphide  used  in  the 
rubber  trade  is  known  as  "  Golden  Sulfide  of  Antimony."  It 
can  be  made  by  boiling  the  crude  black  antimonious  sulfide 
(Sb2Ss)  with  hydrated  lime,  soda  ash,  charcoal  and  sulfur.  The 
mixture  is  then  filtered  and  concentrated  to  crystallization,  giving 
Schlippe's  salt,  NasSbS^  This,  when  treated  with  H2SO4,  pro- 
duces the  orange  pentasulfide,  which  is  allowed  to  settle,  washed 
by  decantation  and  dried.  It  generally  contains  a  considerable 
amount  of  calcium  sulfate,  free  S,  and  antimony  oxide  (Sb20s), 
but  for  rubber  work  should  be  entirely  free  from  acids  and  chlorides. 
The  free  sulfur  generally  ranges  from  5  to  as  much  as  30%;  the 
color  varies  from  a  full  orange-tan  to  almost  purple-scarlet. 
The  behavior  of  different  samples  with  boiling  CS2  varies  widely; 
in  some  cases  reduction  to  Sb2Ss  takes  place.  The  same  is  true 
of  the  behavior  of  different  samples  on  drying  at  110°  C. 

Free  Sulfur. — Weigh  accurately  2  grams  into  a  beaker  and  dis- 
solve the  Sb2Ss  with  cone.  NH4OH.  Filter  the  residue  on  a  filter 
paper,  which  has  been  dried  and  weighed  in  a  weighing  bottle,  and 
wash  with  dilute  NILtOH  until  the  filtrate  shows  no  trace  of  Sb2Ss 
on  acidulation  with  HC1.  Dry  this  filter  paper  and  contents  for 
five  hours  (or  to  constant  weight)  at  a  temperature  not  over  60°  C. 
The  loss  in  weight  is  the  Sb2Ss,  plus  any  moisture  which  may  have 
been  present.  (For  accurate  work  the  moisture  should  be  deter- 
mined on  a  separate  sample  by  drying  at  a  temperature  not  above 
60°  C.) 

Carefully  fold  the  filter  paper,  place  in  an  extraction  thimble 
in  a  Soxhlet  extractor,  and  extract  for  twelve  hours  with  CS2. 
Distill  off  most  of  the  CS2  into  the  top  of  the  Soxhlet,  cool,  and 


GENERAL  INORGANIC  ANALYSES  35 

remove  the  flask.     Evaporate  the  rest  of  the  C&2  spontaneously, 
dry  at  not  over  100°  C.  and  weigh  the  free  sulfur. 

NOTES. — (1)  Before  disconnecting  the  flask  it  must  be  allowed  to  cool 
thoroughly,  as  hot  CS2  will  ignite  spontaneously. 

(2)  In  case  the  determination  of  free  sulphur  alone  is  desired  and  the 
analysis  is  urgent  it  may  be  extracted  directly  with  chloroform  or  with  acetone 
without  the  previous  treatment  with  ammonia. 

Antimony  Oxide  (Antimonious  Acid). — Transfer  the  residue 
from  the  C$2  extraction  to  a  beaker.  Evaporate  off  all  €82  and 
then  dissolve  in  40  cc.  of  HC1.  (If  the  material  does  not  com- 
pletely dissolve  in  HC1,  add  one-third  its  volume  of  HNOs  and 
evaporate  to  dryness.  Then  take  up  the  residue  with  40  cc. 
of  cone.  HC1.)  To  the  HC1  solution  add  1  gram  of  potassium 
chlorate,  boil  until  all  Cl  is  driven  off  and  evaporate  to  about  25  cc. 
Cool  and  add  enough  water  to  dissolve  any  salts  which  may  have 
crystallized.  Add  1-2  grams  of  KI  crystals  and  titrate  with 
0.1  N  thiosulfate,  using  starch  indicator.  Do  not  add  the  starch 
until  the  titration  is  almost  finished.  Carry  out  the  titration  in  an 
Erlenmeyer  flask,  preferably  glass-stoppered,  as  otherwise  iodine 
escapes  when  the  KI  is  added.  The  method  depends  upon  the 
reduction  of  SbCU  to  SbCla  by  the  KI  and  titration  of  the  liber- 
ated iodine. 

CALCULATION. — 1  cc.  0.1  N  thiosulf ate  =  0.00721  gram  Sb2O3. 

=  0.00601  gramSb. 

Calcium  Sulfate. — If  calcium  sulfate  is  present,  it  is  usually 
customary  to  confirm  it  qualitatively  and  report  the  amount 
"  by  difference,"  adding  together  the  percentages  of  moisture,  free 
S,  Sb2$5  and  Sb2Oa  and  subtracting  from  100%. 

REFERENCES. — Weber,  C.  O.:  "The  Chemistry  of  India  Rubber,"  page 
186;  Heil  and  Esch:  "Manufacture  of  Rubber  Goods." 

DETERMINATION  OF  SMALL  AMOUNTS  OF  ARSENIC 

General. — The  three  principal  classes  of  materials  (other  than 
arsenic  salts)  in  which  arsenic  often  has  to  be  determined  are : 

1.  Foods,  drugs,  and  chemicals. 

2.  Wall  papers  and  textiles. 

3.  Arsenic  bronzes. 


36  TECHNICAL  METHODS  OF  ANALYSIS 

The  principal  methods  employed  for  the  first  two  classes  are 
the  Marsh  method  and  various  modifications  of  the  Gutzeit 
method. 

MARSH  METHOD 

The  apparatus  consists  of  a  generating  flask  (an  ordinary 
8-ounce  wide-mouth  bottle  with  a  2-hole  stopper  is  suitable) 
with  a  funnel  tube,  a  U-tube  containing  cotton  moistened  with 
10%  lead  acetate  solution  (to  remove  £[28),  a  CaCb  drying  tube, 
and  a  hard  glass  tube  of  8  mm.  bore  drawn  down  near  the  end  to  a 
uniform  constriction  about  4  cm.  long  and  1  mm.  inside  diameter 
and  also  at  the  very  end  to  a  narrow  exit  tube.  Instead  of  hard 
glass,  transparent  silica  makes  very  satisfactory  tubes.  The 
tube  is  supported  over  a  3-burner  furnace,  the  part  in  contact 
with  the  flame  being  wrapped  with  wire  gauze. 

Introduce  into  the  generating  flask  20-30  grams  of  arsenic-free 
zinc  (either  stick  or  mossy)  and  a  perforated  platinum  disc  to 
produce  an  electric  couple.  Insert  the  stopper  and  add  through 
the  funnel  tube  sufficient  20%  H^SCU  to  start  the  reaction  and 
drive  out  all  air.  When  any  danger  of  explosion  is  over,*  heat  the 
tube  to  bright  redness.  After  running  the  current  long  enough  to 
prove  the  absence  of  arsenic  in  the  reagents,  add  slowly  through 
the  funnel  tube  a  solution  of  the  material  in  20%  H  280,4,  or  the 
solution  obtained  by  one  of  the  procedures  described  below, 
containing  about  20%  of  H2SO4,  keeping  a  steady  evolution  of 
gas.  When  the  flow  slackens,  add  30%  H2SO4  and  later  40% 
H2S04  until  all  the  As  has  been  expelled,  which  usually  takes 
from  two  to  three  hours.  If  no  As  mirror  forms  in  the  constriction 
tube  in  one  hour,  further  test  may  be  abandoned. 

*  Test  for  this  as  follows :  Invert  a  small  test-tube  over  the  capillary  exit 
of  the  Marsh  tube,  in  a  nearly  vertical  position,  so  that  the  test-tube  will  be 
gradually  filled  with  the  generated  gas.  Hold  in  this  position  for  about  one 
minute.  Then  place  the  thumb  over  the  open  end  of  the  test-tube,  reverse 
the  position  of  the  latter,  bring  the  open  end  of  the  tube  near  a  gas  flame  and 
remove  the  thumb.  If  the  tube  is  filled  with  an  explosive  mixture,  the  con- 
tents will  ignite  with  a  peculiar  noise  resembling  the  yelp  of  a  dog.  Repeat 
this  at  intervals  until  the  tube  can  be  filled  with  a  gas  which  is  non-explosive 
and  ignites  quietly.  As  hydrogen  is  lighter  than  air  the  test-tube  must  be 
held  inverted  while  filling  and  then  reversed  when  brought  to  the  flame. 


GENERAL  INORGANIC  ANALYSES  3Y 

If  the  amount  of  As  is  sufficient,  cut  off  the  constriction  from 
the  tube  and  weigh  it,  or  weigh  the  whole  tube.  Then  dissolve  the 
As  in  a  solution  of  sodium  hypochlorite  (Sb  is  insoluble).  Wash 
with  water  and  then  .with  alcohol,  dry,  cool  and  weigh.  The  loss 
is  metallic  arsenic. 

If  the  amount  of  As  is  very  small,  compare  the  mirror  with 
a  series  of  standard  mirrors  prepared  in  the  same  apparatus  using 
quantities  of  a  standard  solution  containing  from  0.005  to  0.05 
mg;  of  As20s.  To  prepare  the  standard  solution,  dissolve  1  gram 
of  pure  AS20s  in  arsenic-free  NaOH  solution.  Acidify  with  H2SO4, 
make  up  to  1  liter  and  dilute  10  cc.  of  this  stock  solution  to  1  liter. 
Of  the  latter  solution  1  cc.  =  0.01  mg.  of 


SANGER-BLACK-GUTZEIT  METHOD  (MODIFIED) 

Reagents.  —  (a)  Cone,  nitric  and  sulfuric  acids,  arsenic-free 
(sp.  gr.  1.42  and  1.84,  respectively). 

(b)  Sulfuric  acid  (1:2). 

(c)  Zinc,  arsenic-free  —  Stick  zinc  broken  into  pieces  approxi- 
mately 1  cm.  in  length. 

(d)  Lead  acetate  paper  —  Heavy  filter  paper  soaked  in  20% 
lead  acetate  solution,  dried  and  cut  into  pieces  about  4.5  by  16  cm. 

(e)  Lead  acetate  cotton  —  Absorbent  cotton  soaked  in  5%  lead 
acetate  solution. 

(/)  Mercuric  bromide  paper  —  Cut  heavy,  close-textured  draft- 
ing paper  (similar  to  Whatman's  cold  pressed)  into  strips  exactly 
2.5  mm.  wide  and  about  12  cm.  long.  Soak  for  an  hour  in  a 
5%  solution  of  HgBr2  in  95%  alcohol,  squeeze  out  the  excess  of 
solution  and  dry  on  glass  rods.  Cut  off  the  ends  of  the  strips 
before  using. 

(d)  20%  potassium  iodide  solution. 

(h)  Stannous  chloride  solution  —  40  grams  of  stannous  chloride 
crystals  made  up  to  100  cc.  with  cone.  HC1. 

(i)  Standard  arsenic  solution  —  Dissolve  1  gram  of  AsoOa  in 
25  cc.  of  20%  NaOH  solution,  neutralize  with  dil.  H2SO4,  add 
10  cc.  of  cone.  H2SO4  and  dilute  to  1  liter  with  recently  boiled 
water.  One  cc.  of  this  solution  contains  1  mg.  of  arsenious 
oxide  (As2Os). 

Dilute  20  cc.  of  this  solution  to  1  liter.     Fifty  cc.  of  the  latter 


38 


TECHNICAL  METHODS  OF  ANALYSIS 


-Mercuric  Bromide 
Paper 


•Lead  Acetate 
Cotton 


solution  when  diluted  to  1  liter  give  a  dilute  standard  solution 
containing  0.001  mg.  of  arsenious  oxide  (As2O,3)  per  cc.,  which 
is  used  to  prepare  the  standard  stains.  The  dilute  solutions  must 
be  freshly  prepared  immediately  before 
use. 

Apparatus. — Use  a  2-ounce  wide- 
mouth  bottle  as  a  generator.  Fit  this 
by  means  of  a  perforated  rubber  stopper 
with  a  glass  tube,  1  cm.  in  diameter  and 
6  cm.  long,  containing  a  piece  of  the  lead 
acetate  paper  rolled  into  a  cylinder. 
Connect  this  tube  by  means  of  a  per- 
forated rubber  stopper  with  a  similar 
tube  filled  with  the  lead  acetate  cotton, 
squeezed  to  remove  excess  of  the  solu- 
tion. The  cotton  in  all  tubes  used  should 
be  uniformly  moist  to  obtain  compara- 
tive stains.  Connect  the  second  tube  by 
means  of  a  perforated  rubber  stopper 
with  a  narrow  glass  tube,  3  mm.  internal 
diameter  and  12  cm.  long,  containing  a 
strip  of  the  mercuric  bromide  paper. 
(See  Fig.  2.)  Rubber  stoppers  used  for 
connections  must  be  free  from  any  white 
coating. 

Preparation  of  Solution. — Weigh  5-50 
grams  of  the  finely  divided  and  well- 
mixed  sample  into  a  porcelain  casserole, 
the  amount  selected  depending  upon  the 
character  of  the  material  and  the  ease  with 
which  it  is  oxidized.  With  dry,  highly 
nitrogenous  substances  employ  5  grams; 
pulped  vegetables,  25  grams;  liquids  with 
low  solid  content,  like  beer  or  vinegar, 
50  grams.  Add  10-15  cc.  of  HNO3, 
cover  the  casserole  by  setting  a  watch 

glass  inside  the  rim,  convex  side  upward,  heat  until  vigorous  action 
is  over,  cool  and  add  10  cc.  of  cone.  H2SO4.  Heat  on  a  wire  gauze 
over  a  flame  until  the  mixture  turns  dark  brown  or  black,  then 


Lead  Acetate 
Paper 


— Solution 


-Stick  Zrac- 


FIG.  2.  —  Sanger-Black- 
Gutzeit  Apparatus  for 
Arsenic  Determination. 


GENERAL  INORGANIC  ANALYSES  39 

add  more  HNOs  in  5  cc.  portions,  heating  between  each  addition 
until  the  liquid  remains  colorless  or  yellow  when  evaporated  until 
SOs  fumes  are  evolved.  To  remove  completely  all  nitric  or 
nitrous  acid,  evaporate  to  about  5  cc.,  cool,  dilute  with  10-15  cc. 
of  water  and  again  evaporate  until  white  SOs  fumes  are  evolved. 
Cool,  dilute  with  water,  again  cool,  and  make  up  with  water  to  a 
definite  volume  (usually  25-100  cc.,  depending  upon  the  amount  of 
sample  taken  and  its  arsenic  content). 

Determination. — Introduce  20  cc.  of  the  solution  or,  if  the 
amount  of  arsenic  is  large,  an  aliquot  containing  not  more  than 
0.03  mg.  of  As20s  prepared  as  directed  under  Preparation  of 
Solution,  into  the  generator  of  the  apparatus  as  described  above 
and  add  20  cc.  of  dil.  EkSCU.  If  the  total  volume  is  less  than  40  cc., 
dilute  to  that  volume  with  water,  and  add  4  cc.  of  20%  KI  solu- 
tion. Heat  to  about  90°  C.,  add  3  drops  of  SnCl2  solution  and 
heat  for  ten  minutes.  Cool  the  generator  and  its  contents  in  a 
pan  containing  water  and  ice;  when  cold,  add  about  15  grams  of 
the  stick  zinc  and  connect  the  entire  apparatus  described  above. 
Keep  the  bottles  in  ice  water  for  fifteen  minutes,  then  remove 
from  the  bath  and  allow  the  evolution  of  gas  to  proceed  for  an 
hour  longer.  Remove  the  sensitized  paper  and  compare  the  stain 
with  similar  ones  produced  under  like  conditions  with  known 
amounts  of  arsenic,  using  portions  of  the  standard  arsenic  solution, 
containing  0.001,  0.002,  0.005,  0.010,  0.015,  0.025  and  0.030  mg.  of 
As2Os,  adding  such  quantities  of  water  and  H^SCU  that  the  same 
volume  and  acid  strength  are  maintained  as  above. 

NOTE. — It  is  very  necessary  in  making  comparisons  that  the  same  apparatus 
be  used  and  the  same  proportions  of  the  same  reagents. 

METHODS  OF  PREPARING  SAMPLES  FOR  TEST 

(1)  Foods,  Drugs,  and  Chemicals. 

(a)  Syrups,  baking  powders  and  other  materials  soluble  in  water 
or  acid  do  not  need  preliminary  treatment. 

(b)  Beer  is  treated  as  follows:  Measure  100  cc.  (freed  from  C02 
by  agitation)  in  a  7-inch  porcelain  evaporating  dish;  add  20  cc.  of 
pure  cone.  HNOs  and  3  cc.  of  pure  cone.  H2SO4  and  heat  cautiously 
until  vigorous  chemical  action  sets  in.     Turn  the  flarne  low,  or 
remove  it  altogether,  and  stir  vigorously  until  the  frothing  ceases, 


40  TECHNICAL  METHODS  OF  ANALYSIS 

after  which  the  liquid  may  be  boiled  freely.  Transfer  to  a  large 
casserole  and  continue  boiling  until  nearly  all  the  HNOs  is  driven 
off.  Then,  holding  the  casserole  by  the  handle,  continue  the 
heating  until  the  mass  chars  and  fumes  of  SOs  are  given  off, 
giving  the  casserole  a  rotary  motion  to  prevent  spattering.  The 
residue  should  be  reduced  to  a  dry,  black  pulverulent  char  soon 
after  the  SOs  fumes  begin  to  come  off  freely.  If  still  liquid,  stir 
in  pieces  of  filter  paper  while  still  heating  until  the  residue  is  dry, 
avoiding  an  excess  of  paper.  Cool,  add  50  cc.  of  water  and 
remove  the  masses  of  char  from  the  sides  of  the  dish  with  a  stirring 
rod.  Heat  to  boiling  and  filter.  Use  the  filtrate  for  the  Marsh 
apparatus,  adding  it  gradually. 

(c)  Meat,  vegetables  and  the  like  may  be  treated  as  follows, 
varying  the  proportion  of  acids  to  suit  the  conditions:  Heat 
at  150-160°  C.  in  a  porcelain  dish  100  grams  of  the  finely  divided 
material  with  23  cc.  of  pure  cone.  HNOs,  stirring  occasionally. 
When  the  mixture  assumes  a  deep  orange  color,  remove  from  the 
heat,  add  3  cc.  of  pure  cone.  H2S04  and  stir  while  nitrous  fumes  are 
given  off.  Heat  to  180°  C.  and  add,  while  still  hot,  drop  by  drop 
with  stirring,  8  cc.  of  HN03.  Then  heat  at  200°  C.  until  S03 
fumes  come  off  and  a  dry  charred  mass  remains.  Pulverize  the 
mass,  extract  with  hot  water,  filter,  evaporate  to  small  volume, 
take  up  in  cold  20%  H2SO4  and  treat  by  the  Marsh  or  Gutzeit 
method. 

ALTERNATIVE  METHOD. — Digest  at  room  temperature  for  some  hours 
5-20  grams  of  the  material  in  a  casserole  with  about  an  equal  bulk  of  HNO3. 
Add  20  cc.  cone.  H2SO4  and  digest  further  at  a  gentle  heat  until  the  mixture 
begins  to  char.  Add  about  2  cc.  of  HNO3  and  heat  until  SO3  fumes  appear, 
repeating  the  addition  of  acid  and  heating  until  oxidation  appears  to  be 
practically  complete.  Remove  all  HNOs  by  dilution  and  evaporation  to  the 
fuming  stage.  Then  dilute  with  4  volumes  of  water.  At  this  point  about 
twice  the  bulk  of  saturated  SC>2  solution  may  be  added  and  the  evaporation 
repeated,  thus  reducing  to  the  arsenious  condition,  but  this  is  not  usually 
necessary. 

(2)  Wall  Paper  and  Textiles.— Take  a  piece  of  paper  3.25X4 
inches  (equivalent  to  0.01  sq.  yd.)  or  a  piece  of  cloth  12X10.8 
inches  (equivalent  to  0.1  sq.  yd.).  Cut  in  small  pieces  and 
place  in  a  porcelain  dish  or  Kjeldahl  flask.  Add  about  50  cc.  of 
a  mixture  of  25  cc.  cone.  H2SO4  and  1  cc.  cone.  HNOa.  Heat  on  a 
low  flame  until  completely  charred,  and  then  continue  heating 


GENERAL  INORGANIC  ANALYSES 


41 


until  strong  fumes  of  SOs  appear.  Cool,  dilute  and  filter  into  a 
liter  flask.  Cool  and  dilute  to  the  mark.  Treat  250  cc.  of  this 
solution  by  the  Gutzeit  method,  using  2  grams  of  arsenic-free 
zinc  and  letting  the  reaction  run  until  the  Zn  is  all  dissolved.  If  a 
strong  reaction  is  obtained,  repeat,  using  a  smaller  aliquot.  A 
very  faint  yellow  color  on  the  paper  indicates  the  following  amounts 
of  metallic  arsenic  per  square  yard : 


Arsenic  (Grains  per  Square  Yard) 

Solution  Taken 

cc. 

Paper 

Cloth 

500 

0.007 

0.0007 

400 

0.009 

0.0009 

300 

0.012 

0.0012 

200 

0.018 

0.0018 

100 

0.036 

0.0036 

10 

0.36 

0.036 

1 

3.6 

0.36 

NOTES. — (1)  The  Massachusetts  law  allows  not  over  0.1  grain  of  metallic 
arsenic  per  square  yard  of  wall  paper  and  not  over  0.01  grain  in  dress  goods. 

(2)  For  court  cases  use  the  Marsh  method  and  compare  with  standards. 

(3)  Determination  of  Arsenic  in  Alloys. — (See  page  149.) 

REFERENCES. — Leach:  "Food  Inspection  and  Analysis,"  1913  Edition, 
pages  74  and  728;  Am.  Chem.  J.  11,  250;  Proc.  Am.  Acad.  Arts  Sci.  26,  24; 
J.  Soc.  Chem.  Ind.  26,  1115  (1907);  J.  Assoc.  Official  Agr.  Chemists,  Methods 
of  Analysis  (1916),  page  171. 

DETERMINATION  OF  POTASSIUM  IN  FERTILIZERS,  SOILS,  PLANT 
ASHES,   ETC.,  AND  IN  POTASH  SALTS 

(A)  LINDO-GLADDING  METHOD 

(1)  Preparation  of  Reagents. — (a)  Ammonium  Chloride  Solution. 
— Dissolve  100  grams  of  NKiCl  in  500  cc.  of  water,  add  5  to  10 
grams  of  pulverized  K^PtCle,  and  shake  at  intervals  for  6-8 
hours.  Let  the  mixture  settle  overnight  and  filter.  The  residue 
may  be  used  for  the  preparation  of  a  fresh  supply. 

(6)  Platinum  Solution. — The  platinum  chloride  solution  used 
contains  1  gram  of  metallic  platinum  (2.1  grams  of  H^PtCle)  per 
10  cc. 


42  TECHNICAL  METHODS  OF  ANALYSIS 

(c)  80%  Alcohol— Sp.  gr.  0.8645  at  15°  C.* 

(2)  Methods  of  Making  Solution. 

(a)  Mixed  Fertilizers. — Place  2.5  grams  of  the  sample  upon  a 
12.5  cm.  filter  paper  and  wash  with  successive  small  portions  of 
boiling  water  till  the  filtrate  is  about  200  cc.  Add  to  the  latter 
2  cc.  of  cone.  HC1  and  heat  to  boiling.  Transfer  to  a  250  cc. 
graduated  flask  and  add  to  the  hot  solution  a  slight  excess  of 
NELiOH  and  sufficient  (NH4)2C2O4  solution  to  precipitate  all  the 
lime  present.  Cool,  dilute  to  250  cc.,  mix,  and  pass  through  a 
dry  filter. 

(6)  Potash  Salts,  Muriate  and  Sulfate  of  Potash,  Sulfate  of 
Potash  and  Magnesia,  and  Kainit. — Dissolve  2.5  grams  and  dilute 
to  250  cc.  without  the  addition  of  NH4OH  and  (NH4)2C2O4. 

(c)  Organic  Compounds. — When  it  is  desired  to  determine  the 
total  amount  of  K^O,  in  organic  substances,  such  as  cottonseed 
meal,  tobacco  stems,  etc.,  saturate  10  grams  with  cone.  H2S04 
and  ignite  in  a  muffle  at  a  low  red  heat  to  destroy  organic  matter. 
Add  a  little  cone.  HC1,  warm  slightly  in  order  to  loosen  the  mass 
from  the  dish,  and  proceed  as  directed  above  for  Mixed  Ferti- 
lizers (a). 

(3)  Determination. 

(a)  Mixed  Fertilizers. — Evaporate  50  cc.  of  the  solution  made 
according  to  (2),  corresponding  to  0.5  gram  of  the  sample,  nearly 
to  dryness,  add  1  cc.  of  dil.  H2SO4  (1:1),  evaporate  to  dry- 
ness,  and  ignite  to  perfect  whiteness.  All  K20  is  in  the  form  of 
non-volatile  K2SO4  and  a  full  red  heat  must  be  maintained  until 
the  residue  is  perfectly  white.  Dissolve  the  residue  in  hot  water, 
using  at  least  20  cc.  for  each  0.1  gram  of  K^O.  Add  a  few  drops  of 
HC1  and  an  excess  of  the  platinum  solution.  Evaporate  on  a 
water  bath  to  a  -thick  paste  in  a  porcelain  dish  and  treat  the 
residue  with  80%  alcohol,  avoiding  exposure  to  NH%.  Filter 
and  wash  the  precipitate  thoroughly  with  80%  alcohol  both  by 
decantation  and  on  the  filter,  continuing  the  washing  after  the  fil- 
trate is  colorless.  Wash  finally  with  10  cc.  of  NEUCl  solution 
(1,  a)  to  remove  impurities  from  the  precipitate,  and  repeat  this 
washing  5  or  6  times.  Wash  again  thoroughly  with  80%  alcohol 

*  Denatured  alcohol,  made  up  according  to  formula  30  (U.  S.  I.  R.  Reg. 
No.  30,  revised)  and  diluted  with  water  to  make  80%  by  volume  may  also  be 
used. 


GENERAL  INORGANIC  ANALYSES  43 

and  dry  the  precipitate  for  thirty  minutes  at  100°  C.     Weigh  as 
K2PtCl6  and  calculate  to  K2O. 

NOTE. — The  precipitate  should  be  completely  soluble  in  water. 

(b)  Muriate  of  Potash. — Acidify  50  cc.  of  the  solution  prepared 
according  to  (2,  6)  with  a  few  drops  of  HC1,  add  10  cc.  of  platinum 
solution  and  evaporate  to  a  thick  paste.     Treat  the  residue  as 
under  (3,  a). 

(c)  Sulfate  of  Potash,  Sulfate  of  Potash  and  Magnesia,   and 
Kainit. — Acidify  50  cc.  of  the  solution,  prepared  according  to 
(2,  b)  with  a  few  drops  of  HC1  and  add  15  cc.  of  platinum  solution. 
Evaporate  the  mixture  and  proceed  as  directed  under   (3,  a), 
except  that  25  cc.  portions  of  NHiCl  solution  should  be  used. 

(d)  Water-soluble  Potash   in    Wood  Ashes   and    Cotton    Hull 
Ashes. — Use  the  above  method,  making  the   solution    according 
to  (2,  a)  and  pay  special  attention  to  the  note  under  (3,  a). 

(4)  Factors. — For  the  conversion  of  •  K^PtCle  to  KC1,  use 
the  factor  0.3067;  to  K2SO4,  0.3584;  and  to  K2O,  0.1938. 

(B)  OPTIONAL  METHOD 
NOTE. — Method  (A)  is  preferable  in  the  presence  of  soluble  sulphates. 

Reagents. — The  same  as  for  the  Lindo-Gladding  method  (A). 

Preparation  of  Solution. — Prepare  the  solution  as  directed 
under  the  Lindo-Gladding  method  (A,  2)  omitting  in  all  cases  the 
addition  of  ammonium  hydroxide  and  oxalate. 

Determination. — Dilute  25  cc.  of  the  solution  (50  cc.  if  less 
than  10%  of  K2O  is  present)  to  150  cc.  Heat  to  boiling  and  add, 
drop  by  drop,  and  with  constant  stirring,  a  slight  excess  of  BaCl2 
solution.  Without  filtering,  add  in  the  same  manner  Ba(OH)2 
solution  in  slight  excess.  Filter  while  hot  and  wash  until  the 
precipitate  is  free  from  Cl.  Add  to  the  filtrate  1  cc.  of  cone. 
NHiOH  and  then  a  saturated  solution  of  ammonium  carbonate 
until  the  excess  of  Ba  is  precipitated.  Heat  and  add,  in  fine  pow- 
der, 0.5  gram  of  pure  oxalic  acid  or  0.75  gram  of  (NH4)2C204. 
Filter,  wash  free  from  Cl,  evaporate  the  filtrate  to  dry  ness  in  a 
platinum  dish  and  ignite  carefully  over  the  free  flame  below  red 
heat  until  all  volatile  matter  is  driven  off.  Digest  the  residue  with 
hot  water,  filter  through  a  small  filter  and  dilute  the  filtrate, 


44  TECHNICAL  METHODS  OF  ANALYSIS 

if  necessary,  so  that  for  each  0.1  gram  of  K^O  there  will  be  at 
least  20  cc.  of  liquid.  Acidify  with  a  few  drops  of  HC1  and  add 
platinum  solution  in  excess.  Evaporate  in  a  porcelain  dish  on  the 
water  bath  to  a  thick  paste  and  treat  the  residue  with  80%  alcohol, 
both  by  decantation  and  after  collecting  on  a  weighed  Gooch. 
Dry  for  thirty  minutes  at  100°  C.  and  weigh.  If  there  is  an 
appearance  of  foreign  matter  in  the  precipitate,  it  should  be 
washed  as  described  above  under  Method  (A)  with  several  portions 
of  10  cc.  each  of  the  NEUCl  solution. 

(C)  J.  LAWRENCE  SMITH  METHOD 
For  Rocks  and  Silicious  Materials 

Mix  0.5  gram  of  the  sample,  finely  ground,  with  0.5  gram  of 
pure  dry  NHUCl,  by  gentle  trituration  in  an  agate  mortar,  then  add 
4  grams  of  dry  powdered  CaCOs  and  mix  intimately.*  Place  the 
mixture  in  a  large  platinum  crucible,  rinsing  the  mortar  with  a 
little  of  the  CaCOs  powder.  Place  the  crucible  in  a  hole  cut  in  a 
sheet  of  asbestos,  the  hole  of  such  a  size  that  not  more  than  two- 
thirds  of  the  crucible  will  be  below  the  asbestos.  Heat  very  gently 
over  a  small  Bunsen  burner  until  fumes  of  NELt  salts  no  longer 
appear.  Then  heat  with  a  higher  flame  until  the  lower  part  of  the 
crucible  is  brought  to  a  red  heat.  Not  more  than  three-quarters 
of  the  crucible  should  be  red  and  it  should  be  kept  well  covered 
during  the  fusion.  Keep  this  temperature  constant  for  forty 
to  sixty  minutes. 

The  temperature  desired  is  that  which  suffices  to  keep  in  a 
state  of  fusion  the  CaCU  formed  by  the  reaction  of  NHiCl  with 
CaCOs.  The  mass,  however,  does  not  become  liquid,  since  the 
fused  CaCl2  is  absorbed  by  the  large  quantity  of  CaC03  present. 
The  silicate  itself  should  not  fuse,  since  this  would  render  impos- 
sible the  disintegration  of  the  mass  at  the  end  of  the  operation. 
Moreover,  too  high  a  temperature  causes  a  volatilization  of  alkali 
chlorides.  Certain  silicates,  e.g.,  those  which  contain  much  ferrous 
iron,  may  fuse  when  heated  with  the  above  mixture,  even  if  no 
higher  temperature  is  employed  than  is  necessary  to  effect  decom- 
position. If  this  occurs,  it  is  better  to  repeat  the  ignition  with  a 
new  portion,  using  8-10  parts  of  CaCOs. 

*  For  soils  double  the  above  amounts. 


GENERAL  INORGANIC  ANALYSES  45 

The  mass  contracts  in  volume  during  the  ignition,  and  is 
usually  easily  detached  from  the  crucible.  Boil  it  for  0.5  hour  in  a 
covered  porcelain  dish  with  50-75  cc.  of  water,  replacing  water 
lost  by  evaporation.  Decant  the  solution  from  the  residue  upon 
a  filter,  boil  the  residue  a  few  minutes  with  water,  and  decant 
again.  If  the  residue  is  now  all  in  a  finely  disintegrated  state, 
it  may  be  brought  upon  the  filter  and  washed.  But  if,  as  is  often 
the  case,  a  portion  remains  coherent  or  in  a  coarsely  granular 
state,  it  must  be  reduced  to  a  fine  state  of  division  by  trituration 
with  a  porcelain  or  agate  pestle  in  the  dish,  and  boiling  with  water 
again.  By  a  few  repetitions  of  the  trituration,  boiling  and  decant- 
ing, allowing  the  fine  suspended  portion  to  pass  upon  the  filter 
each  time,  the  whole  can  usually  be  transferred  to  the  filter  in 
properly  disintegrated  condition  in  the  course  of  an  hour. 

Next  wash  until  a  few  drops  of  the  washings  acidified  with 
HNOs  give  but  a  slight  turbidity  with  AgNOs.  The  filtrate  now 
contains  the  alkalies  of  the  silicate  as  chlorides  together  with  cal- 
cium chloride  and  hydroxide.  It  is  not  advisable  to  concentrate 
this  filtrate  in  glass,  since  it  might  dissolve  an  appreciable  quan- 
tity of  sodium.  Precipitate,  therefore,  the  Ca  at  once  with  ammo- 
nium carbonate;  let  the  precipitate  settle,  and  concentrate  the 
supernatant  solution  in  a  porcelain  (or  platinum)  dish,  decanting 
it  into  the  latter,  portionwise  if  necessary,  finally  rinsing  the  pre- 
cipitate into  the  porcelain  dish.  When  the  whole  is  thus  reduced 
to  about  30  cc.,  add  a  little  more  ammonium  carbonate  and 
NH4OH,  heat  and  filter  into  a  platinum  (or  porcelain)  dish.  Evap- 
orate to  dryness  on  a  water  bath,  expel  NILtCl  by  gentle  ignition, 
and  dissolve  the  residual  alkali  chlorides  in  3-5  cc.  of  water. 

A  little  black  or  dark-brown  flocculent  matter  usually  remains 
undissolved,  and  the  solution  may  still  contain  traces  of  Ca. 
Add  2  or  3  drops  of  ammonium  carbonate  and  NEUOH,  warm 
gently,  and  filter  through  a  very  small  filter  into  an  unweighed 
but  weighable  platinum  dish.  Evaporate  to  dryness  on  a  water 
bath,  heat  at  dull  red  to  incipient  fusion  of  the  alkali  chlorides 
and,  after  cooling,  weigh.  Dissolve  the  mixed  chlorides  in  water 
and  filter  through  a  small  filter  into  a  porcelain  dish.  Ignite  the 
filter  in  the  platinum  vessel  previously  used  and  weigh.  Sub- 
tract this  weight  from  the  first  weight  to  obtain  the  weight  of  the 
NaCl+KCl.  Determine  the  K^O  in  the  filtrate  in  the  porcelain 


46  TECHNICAL  METHODS  OF  ANALYSIS 

dish  by  precipitating  with  platinum  chloride  as  previously  described, 
adding  sufficient  platinum  chloride  to  combine  with  the  total 
weight  of  alkali  chlorides  calculated  as  Nad,  i.e.,  an  amount  of 
metallic  Pt  1.67  times  the  weight  of  alkali  chlorides  found. 

NOTES. — (1)  Smith's  method  is  the  most  convenient  of  all  methods  for 
extracting  alkalies  from  silicates,  and  is  universally  applicable,  except  perhaps 
in  the  presence  of  boric  acid.  When  carried  out  as  here  described,  results  are 
sufficiently  accurate  in  most  cases.  If,  however,  the  silicate  is  rich  in  alkalies,  a 
loss  amounting  to  0.1  or  0.2%  of  the  mineral  is  possible.  If  great  accuracy 
is  desired  in  such  cases,  a  repetition  of  the  whole  process  may  be  applied  to  the 
residue  left  by  treatment  of  the  ignited  mass  with  water.  It  need  hardly  be 
mentioned  that  unless  care  be  taken  to  use  reagents  perfectly  free  from  soda 
and  to  avoid  action  of  the  solution  on  glass,  an  amount  of  soda  may  be  intro- 
duced from  these  sources  equal  to  0.1  or  0.2%. 

(2)  The  above  methods  are  the  official  methods  of  the  Assoc.  Official  Agr. 
Chemists.  The  factors  are  based  on  1920  atomic  weights. 

REFERENCES. — Journal  Assoc.  Official  Agr.  Chemists,  Methods  of  Analy- 
sis (1916),  pages  12,  24,  26;  Fresenius:  ' 'Quantitative  Chemical  Analysis," 
page  426. 

LEAD  ARSENATE 

General. — Lead  arsenate,  furnished  on  the  market  as  an 
insecticide,  generally  consists  either  of  Pb3(AsO4)2  or  PbHAsO4 
or  a  mixture  of  the  two.  The  former  is  prepared  from  lead  acetate 
and  sodium  arsenate  according  to  the  reaction: 

3Pb(C2H302)2  •  3H2O+2Na2HAsO4  •  7H2O 

=  Pb3(AsO4)2+4NaC2H3O2-3H2O+2HC2H3O2+llH2O. 

The  second  form  is  made  from  lead  nitrate  and  sodium  arsenate, 
probably  according  to  the  reaction: 

Pb(NO3)2+Na2HAs04  •  7H2O  =  PbHAs04+2NaNO3+7H20. 

Pb3(AsO4)2  contains  theoretically  74.44%  of  PbO  and  25.56% 
of  As20s.  On  the  other  hand,  PbHAsO4  contains  theoretically 
64.29%  of  PbO,  33.11%  of  As2O5  and  2.60%  of  water  of  con- 
stitution. In  technical  analysis  it  is  often  customary  to  report 
the  sum  of  the  total  PbO+As205  as  "  Lead  Arsenate."  To  give 
the  seller  full  benefit,  however,  this  sum  should  be  divided  by 
0.9740  and  the  result  reported  as  lead  arsenate,  thus  allowing 
for  the  maximum  amount  of  water  of  constitution. 


GENERAL  INORGANIC  ANALYSES  47 

Total  Volatile  Matter  (Moisture,  etc.). — In  case  the  sample 
is  in  the  form  of  a  paste,  as  it  usually  is,  it  should  be  very  thor- 
oughly and  rapidly  mixed  and  about  50  grams  dried  to  constant 
weight  in  a  flat  glass  Petri  dish  at  105°  C.  and  the  total  loss  in 
weight  determined.  Save  a  portion  of  the  original  paste  t  for 
determination  of  free  acetic  acid  and  free  ammonia,  if  these  deter- 
minations are  desired. 

Grind  the  dried  sample  to  a  fine  powder.  Mix  well,  transfer  a 
small  portion  to  a  sample  bottle  and  again  dry  for  one  to  two  hours 
at  105-110°  C.  Use  this  anhydrous  material  for  the  determination 
of  total  PbO  and  total  As2Os. 

Total  Lead  Oxide. — Dissolve  2  grams  of  the  dry  powder  in 
50  cc.  of  HNOs  (1  :  4)  on  the'  steam  bath.  The  sample  should 
dissolve  without  residue.  (In  case  there  is  an  appreciable  residue, 
it  may  be  filtered  out,  ignited  and  weighed  and  reported  as  Insol- 
uble Matter.) 

Transfer  to  a  250  cc.  volumetric  flask,  cool  to  room  tempera- 
ture and  make  up  to  the  mark.  Pipette  50  cc.  of  this  solution 
into  a  400  cc.  beaker;  dilute  to  at  least  300  cc.;  heat  nearly  to 
boiling;  add  NH^OH  to  incipient  precipitation  and  then  dilute 
HNOs  (1  :  10)  to  redissolve  the  precipitate,  avoiding  more  than 
1-2  cc.  excess.  Add  slowly  from  a  pipette  a  hot  solution  of  K2Cr04 
or  K2Cr207  until  an  excess  is  indicated  by  the  yellow  color  of  the 
solution.  Boil  for  two  or  three  minutes.  The  PbCr04  will  settle 
out,  leaving  a  clear  solution,  in  about  fifteen  minutes. 

Filter  on  a  weighed  Gooch  crucible,  washing  thoroughly  by 
decantation  with  hot  water.  Dry  to  constant  weight  at  140- 
150°  C.  and  calculate  to  PbO. 

CALCULATION.— PbCrO4  X  0.6906  =  PbO. 

NOTES. — (1)  The  PbCKX  may  contain  a  small  amount  of  lead  arsenate 
which  causes  slightly  high  results.  This  error  rarely  amounts  to  more  than 
0.1-0.2%. 

(2)  Instead  of  drying  the  PbCrO4  at  140-150°  C.  it  is  permissible  to  dry 
at  105°  C.,  then  place  the  Gooch  in  a  larger  platinum  crucible  and  ignite  at 
dull  redness.  The  flame  must  not  come  in  direct  contact  with  the  PbCrO4. 

Total  Arsenic  Oxide.— Transfer  100  cc.  of  the  HN03  solution 
prepared  above  to  a  porcelain  or  platinum  dish,  add  6  cc.  of  cone. 
H2S04,  evaporate  to  a  syrupy  consistency  on  the  water  bath 
and  then  on  the  hot  plate  to  copious  white  fumes.  Cool,  wash 


48  TECHNICAL  METHODS  OF  ANALYSIS 

into  a  100  cc.  volumetric  flask  with  water,  and  make  up  to 
the  mark.  Filter  through  a  dry  filter  and  use  a  50  cc.  aliquot 
for  analysis.  Transfer  this  to  a  400  cc.  Erlenmeyer  flask,  add 
about  200  cc.  of  water,  4  cc.  of  cone.  H2S04  and  1  gram  of  KI 
crystals.  Boil  until  the  solution  is  colorless  or  only  faint  yellow. 
The  volume  must  not  be  allowed  to  become  less  than  50  cc.  Cool 
the  solution  under  running  water,  dilute  to  about  300  cc.  and  add 
a  little  starch  solution.  If  this  colors  the  solution  blue,  add  a  drop 
or  two  of  0.1  N  Na2S2Os  until  the  color  is  just  discharged,  then  add 
a  drop  of  methyl  orange  indicator  and  powdered  Na2CO3,  cau- 
tiously at  first  to  avoid  loss  by  foaming.  When  the  solution,  after 
mixing,  becomes  yellow,  add  just  enough  dil.  H^SCX  to  produce  a 
pink  color;  and  then  make  alkaline  again  with  an  excess  of 
NaHCOs  powder.  Add  a  considerable  excess  of  bicarbonate. 
Finally  titrate  the  solution  with  0.05  N  or  0.1  N  iodine  solution 
to  the  appearance  of  a  blue  color  throughout  the  solution. 
CALCULATION.  —  1  cc.  0.1  N  iodine  =  0.005748  gram  As2C>5. 

NOTE.  —  A  generous  excess  of  bicarbonate  insures  a  sharp  end    point  in 
titrating. 


Lead  Arsenate.  —  Add  together  the  total  PbO   and 
divide  the  sum  by  0.9740  and  report  the  result  as  lead  arsenate. 

Total  Water-soluble  Matter.  —  Weigh  to  0.01  gram  about  4 
grams  of  paste  (or  2  grams  if  the  sample  is  a  dry  powder),  place 
in  a  tightly  stoppered  flask  or  bottle  with  250  cc.  of  freshly  boiled 
and  cooled  distilled  water  for  each  gram  of  paste  and  keep  at  32°  C. 
for  twenty-four  hours,  shaking  well  every  hour  of  the  working  day 
(8  times  in  all),  filtering  at  the  end  of  twenty-four  hours.  It  is 
generally  most  satisfactory  to  filter  through  a  Gooch  crucible, 
rinsing  out  the  filtering  flask  once  or  twice  with  the  first  portions  of 
filtrate  and  discarding  them.  Continue  the  filtration  until  about 
350  cc.  of  filtrate  have  been  obtained.  Fill  with  this  a  graduated 
250  cc.  flask,  first  rinsing  the  latter  several  times  with  small  por- 
tions of  the  liquid.  Evaporate  the  entire  250  cc.  in  a  weighed 
platinum  dish  to  dryness  on  the  steam  bath.  Dry  to  constant 
weight  at  100°  C.  and  weigh  the  total  soluble  matter.  The  weight 
in  centigrams  gives  the  direct  percentage. 

NOTE.  —  In  most  cases  it  is  sufficiently  accurate  to  let  stand  for  two  or 
three  days  at  room  temperature  (shaking  frequently),  instead  of  twenty-four 


GENERAL  INORGANIC  ANALYSES  49 

hours  at  32°  C.     The  individual  for  whom  the  analysis  is  made  often  specifies 
the  time  for  digesting  for  water-soluble  impurities. 

Water-soluble  PbO. — Dissolve  the  residue  of  total  soluble 
matter,  above  determined,  in  a  small  amount  of  water,  add  a 
few  cc.  of  cone.  HNOs  and  evaporate  nearly  to  dryness  on  the 
steam  bath;  wash  this  into  a  small  beaker  with  a  little  water,  add 
1  cc.  of  cone.  H2S04,  evaporate  to  a  syrup  on  the  steam  bath  and 
then  to  white  fumes  on  the  hot  plate.  Cool,  add  10  cc.  of  water; 
and  swirl  the  beaker  gently  to  throw  any  PbSCU  into  the  center. 
If  any  is  present,  let  stand  one  hour,  or  for  very  accurate  work, 
overnight.  Then  filter  on  a  tiny  filter,  and  wash  with  5%  H^SCU 
solution.  Dry  the  filter  paper  and  ignite  in  a  weighed  porcelain 
crucible.  Treat  the  residue  with  a  little  HNOs,  which  is  after- 
wards evaporated  off,  and  then  with  a  drop  or  two  of  H2S04. 
Ignite  gently,  cool  and  weigh  as  PbSC>4.  Calculate  to  PbO. 

CALCULATION.— PbS04  X  0.7360  =  PbO. 

Water-soluble  AS2O5. — Water-soluble  As205  is  determined 
in  the  filtrate  from  the  water-soluble  PbO  in  exactly  the  same  man- 
ner as  for  total  As2Os  above,  using,  however,  0.01  N  instead  of 
0.1  N  iodine  for  titration.  It  is  important  that  the  solution  shall 
be  perfectly  clear  and  the  titration  carefully  made.  Make  correc- 
tions for  the  iodine  necessary  to  produce  the  same  color  using  the 
same  chemicals  and  volumes  of  solution.  (See  note  (2)  at  end 
of  method.) 

Free  Acetic  Acid. — Weigh  out  2-10  grams  of  the  original  moist 
sample  and  transfer  to  a  250  cc.  flask  with  20-40  cc.  of  water. 
Connect  with  a  condenser  and  heat  to  boiling.  Pass  steam 
through  the  solution,  regulating  the  flame  under  the  flask  so  that 
the  volume  will  remain  nearly  constant,  and  collect  about  200  cc.  of 
distillate.  Titrate  the  distillate  with  0.1  N  NaOH  and  phenol- 
phthalein,  and  calculate  to  acetic  acid. 

CALCULATION. — 1  cc.  0.1  N  caustic  =  0.0060  gram  HC2HsO2. 

Free  Ammonia. — Wash  2-10  grams  of  the  original  sample 
into  a  200  cc.  distilling  flask  and  dilute  to  about  150  cc.  Concen- 
trate by  distillation  to  about  25  cc.  and  collect  the  distillate  in 
0.1  N-HC1.  Titrate  the  excess  of  HC1  with  standard  alkali,  using 
methyl  red  or  cochineal  indicator,  and  calculate  the  NHs  from  the 
amount  of  acid  consumed. 

CALCULATION.— 1  cc.  0.1  N  HC1  =  0.0017  gram  NH3. 


50  TECHNICAL  METHODS  OF  ANALYSIS 

Calculation  of  Results. — From  the  total  loss  on  drying  sub- 
tract any  free  acetic  acid  or  free  ammonia  which  the  sample  may 
contain,  and  report  the  difference  as  Moisture.  In  case  free 
acetic  acid  and  free  ammonia  are  not  determined,  it  is  customary 
to  report  the  total  loss  on  drying  as  Moisture,  loss  at  105°  C. 

The  percentages  of  total  PbO,  total  As2O5,  and  water-soluble 
impurities  should  be  calculated  to  the  absolute  dry  basis.  These 
results  should  then  be  calculated  to  the  original  paste  by  multiply- 
ing each  by  100%  minus  the  per  cent  of  total  moisture  at  105°  C. 
Subtract  the  per  cent  of  soluble  As20s  and  of  soluble  PbO  from 
the  total  soluble  matter  and  report  the  difference  as  "  Soluble 
impurities." 

NOTES. — (1)  The  procedures  for  Moisture,  Total  PbO,  Total  As2O5,  and 
Water-soluble  As2O5  are  essentially  the  methods  of  the  Association  of  Official 
Agricultural  Chemists  as  published  in  its  Journal,  Methods  of  Analysis 
(1916),  page  67,  slight  changes  being  made  for  convenience  in  conforming  to 
our  usage. 

(2)  Lead  arsenate  as  now  made  seldom  contains  an  appreciable  amount  of 
water-soluble  PbO,  consequently  the  water-soluble  As2O5  can  be  determined 
directly  on  the  filtered  solution  without  going  through  the  steps  of  removing 
lead. 


BORDEAUX  MIXTURE 

General. — Standard  Bordeaux  Mixture  is  made  up  in  the  pro- 
portions of  6  pounds  of  CuS04  and  4  pounds  of  lime  to  50  gallons 
of  water;  but  a  more  common  mixture  is  5  :  5  :  50,  and  for  peach 
trees  the  general  mixture  is  3  :  9  :  50. 

The  following  procedures  are  essentially  the  official  methods 
of  the  Association  of  Official  Agricultural  Chemists. 

NOTE. — Bordeaux  Mixture  is  often  mixed  with  other  insecticides.  For 
analysis  of  such  mixtures  see  page  52. 

Moisture. — (A)  Powder. — Dry  2  grams  to  constant  weight  at 
105-110°  C.  and  express  the  loss  in  weight  as  moisture. 

(B)  Paste.— Beat  about  100  grams  in  the  oven  at  90-100°  C.  un- 
til dry  enough  to  powder  readily  and  determine  the  loss  in  weight. 
Powder  this  partly  dried  sample  and  determine  the  remaining 
moisture  in  2  grams  as  for  powder  above.  Determine 


GENERAL  INORGANIC  ANALYSES  51 

directed  later,  both  in  the  original  paste  and  in  this  partially  dried 
sample.     Calculate  the  total  moisture  by  the  following  formula: 

(100-a)  (6+c) 


in  which  M=per  cent  total  moisture  in  original  paste; 

a  =  per  cent  loss  in  weight  of  first  drying; 

b  =  per  cent  loss  in  weight  of  second  drying  ; 

c  =  per  cent  CO2  in  paste  after  first  drying; 
and  d  =  per  cent  total  CCb  in  original  paste. 


Carbon  Dioxide.  —  (A)  Apparatus.  —  This  consists  of  a  200  cc. 
Erlenmeyer  flask  closed  with  a  2-hole  stopper;  one  of  these  holes 
is  fitted  with  a  dropping  funnel,  the  stem  of  which  extends  almost 
to  the  bottom  of  the  flask;  the  outlet  of  a  condenser,  which  is 
inclined  upward  at  an  angle  of  30°  from  the  horizontal,  passes 
downward  through  the  other  hole.  The  upper  end  of  the  con- 
denser is  connected  with  a  CaC^  tube  which  in  turn  is  connected 
with  a  double  U-tube  filled  in  the  middle  with  pumice  fragments, 
previously  saturated  with  CuSO*  solution  and  subsequently 
dehydrated,  and  with  CaCl2  at  either  end.  Then  follow  two 
weighed  U-tubes  for  absorbing  the  CO2,  the  first  filled  with  porous 
soda-lime,  and  the  second,  one-third  with  soda-lime  and  two- 
thirds  with  CaCU,  the  latter  reagent  being  placed  at  the  exit 
end  of  the  train.  A  Geissler  bulb,  partly  filled  with  H2SO4,  is 
attached  to  the  last  U-tube  to  show  the  rate  of  gas  flow.  An 
aspirator  is  connected  with  the  Geissler  bulb  to  draw  air  through 
the  apparatus.  An  absorption  tower  filled  with  soda-lime  is  con- 
nected with  the  mouth  of  the  dropping  funnel  to  remove  CC>2 
from  the  air  entering  the  apparatus. 

(B)  Determination.  —  Weigh  2  grams  of  the  dry  powder, 
or  10  grams  of  paste,  into  the  Erlenmeyer  flask,  add  about 
20  cc.  of  water,  attach  the  flask  to  the  apparatus,  omitting  the 
2  weighed  U-tubes,  and  draw  CO2-free  air  through  the  apparatus 
until  the  original  air  is  displaced.  Then  attach  the  weighed  U- 
tubes  in  the  position  as  described  above,  close  the  stop-cock  of 
the  dropping  funnel,  fill  half  full  with  dil.  HC1  (1:1),  reconnect 
with  the  soda-lime  tower,  and  let  the  acid  flow  into  the  Erlen- 
meyer flask,  slowly  if  there  is  much  CO2,  rapidly  if  there  is  little. 


52  TECHNICAL  METHODS  OF  ANALYSIS 

When  effervescence  diminishes,  place  a  low  Bunsen  flame  under 
the  flask  and  start  the  flow  of  water  through  the  condenser,  a  slow 
current  of  air  being  allowed  to  flow  through  the  apparatus  at  the 
same  time.  Maintain  a  steady  but  quiet  ebullition,  and  a  slow 
air  current  through  the  apparatus.  Boil  for  a  few  minutes  after 
water  has  begun  to  condense  in  the  condenser,  then  remove  the 
flame  and  continue  the  aspiration  of  air  at  the  rate  of  about  2 
bubbles  per  second  until  the  apparatus  is  cool.  Disconnect  the 
tared  absorption  tubes,  cool  in  the  balance  case  and  weigh.  The 
increase  in  weight  is  due  to  C02. 

Copper. — Dissolve  2  grams  of  the  dry  powdered  sample  in 
about  75  cc.  of  water  and  20  cc.  of  cone.  HNOs  in  a  250  cc.  beaker. 
Dilute  to  200  cc.,  and  electrolyze  as  described  in  the  method  for 
Brass  and  Bronze,  page  145.  Calculate  per  cent  of  Cu  in  the 
sample.  Test  the  solution  to  make  sure  all  Cu  has  been  removed. 

REFERENCE. — J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis  (1916", 
page  69. 

BORDEAUX  MIXTURE  WITH  PARIS  GREEN  AND  LEAD  ARSENATE 

General. — Bordeaux  Mixture  is  often  mixed  with  other  insecti- 
cides and  sold  under  various  names.  "  Pyrox  "  is  generally  a 
mixture  of  copper  and  lead  arsenates,  or  Paris  Green,  with  Bor- 
deaux Mixture.  The  following  procedures  are  those  of  the 
Association  of  Official  Agricultural  Chemists. 

BORDEAUX  MIXTURE  WITH  PARIS  GREEN 

Moisture  and  Carbon  Dioxide  (Official). — These  are  deter- 
mined as  in  Bordeaux  Mixture. 

Copper. — Method  I  (Tentative). — Dissolve  2  grams  of  the  dry 
powdered  sample  in  a  few  cc.  of  cone.  HNOs,  add  25  cc.  of  a  3% 
solution  of  H2O2  and  warm  for  5-10  minutes.  Make  slightly 
alkaline  with  NHiOH  and  then  slightly  acid  again  with  dil.  HNOs. 
Transfer  to  a  weighed  150  cc.  platinum  dish,  add  15-20  cc.  of 
H2O2,  dilute  to  100  cc.  and  electrolyze,  using  a  rotating  spiral 
anode  and  a  current  not  exceeding  2  amperes.  After  electrolysis 
has  proceeded  for  about  twenty  minutes,  add  to  the  electrolyte 
0.5  gram  of  ferric  sulfate  dissolved  in  a  few  cc.  of  water  together 
with  a  drop  or  two  of  HNOs.  After  all  Cu  is  deposited,  wash  the 


GENERAL  INORGANIC  ANALYSES  53 

deposit  with  water  by  siphoning,  then  rinse  with  alcohol,  dry  for  a 
few  minutes  in  the  oven,  weigh  and  calculate  the  per  cent  of  Cu. 
(Do  not  pass  the  current  for  more  than  five  to  ten  minutes  after 
all  the  copper  has  been  deposited  without  adding  more  ferric 
sulfate  solution.) 

Method  II.  (Tentative). — Treat  1  gram  of  the  dry,  powdered 
sample  with  20  cc.  of  water  and  5-6  cc.  of  cone.  HNOs,  heat  to 
boiling,  cool,  and  add  a  slight  excess  of  cone.  NB^OH.  Wash  the 
solution  and  precipitate  into  a  150  cc.  weighed  platinum  dish,  and 
electrolyze,  using  a  rotating  anode  and  a  current  of  about  4 
amperes  and  3-4  volts  for  about  ninety  minutes  (or  until  all  Cu  is 
deposited).  Wash  the  deposit  by  siphoning  until  it  is  clean,  being 
careful  not  to  use  too  much  wash  water.  Dissolve  the  Cu  in  5  cc. 
of  cone.  HNOs,  dilute  to  100  cc.  and  electrolyze  as  before,  except 
that  all  the  Cu  will  be  deposited  in  thirty  minutes.  Wash  the 
deposit  with  water  by  siphoning,  then  rinse  with  alcohol,  dry 
for  a  minute  or  so  in  an  oven,  weigh  and  calculate  the  per  cent  of  Cu. 

Total  Arsenic  (Official)  .• — Proceed  as  directed  for  Total  Arsenic 
in  Paris  Green  (page  55)  using  an  amount  of  the  dry,  powdered 
sample  equal  to  the  As2Os  equivalent  of  500  cc.  of  the  standard 
iodine  solution.  The  number  of  cc.  of  the  standard  iodine  solution 
used,  divided  by  2,  represents  directly  the  per  cent  of  total  arsenic 
in  the  sample,  expressed  as  As203. 

Total  Arsenious  Oxide  (Tentative). — Proceed  as  directed  for 
Total  Arsenious  Oxide  in  Paris  Green  (page  56)  using  an  amount 
of  the  dry,  powdered  sample  equal  to  the  As2Os  equivalent  of  200 
cc.  of  the  standard  iodine  solution.  Before  titrating,  all  Cu  must 
be  in  solution.  The  corrected  number  of  cc.  of  the  standard  iodine 
solution  used,  divided  by  2,  represents  directly  the  total  As2Os 
in  the  sample. 

Water-soluble  Arsenious  Oxide  (Tentative). — Proceed  as 
described  under  Water-soluble  Arsenious  Oxide  in  Paris  Green 
(page  57),  using  2  grams  of  the  sample,  and  slightly  acidify  with 
HC1  the  aliquot  employed  before  adding  the  excess  of  NaHCOs. 


54  TECHNICAL  METHODS  OF  ANALYSIS 


BORDEAUX  MIXTURE  WITH  LEAD  ARSENATE 

Moisture  and  Carbon  Dioxide  (Official). — Proceed  as  above 
described. 

Copper  (Tentative). — Proceed  as  above  described,  using 
Method  II. 

Lead  Oxide  (Tentative). — Dissolve  the  PbO2  (which  will 
contain  a  little  arsenic)  from  the  anodes  used  in  the  copper  elec- 
trolysis, under  Method  II,  by  means  of  dil.  HNOs  and  a  little 
H2O2,  and  add  to  this  solution  the  washings  from  both  electrolyses 
of  Cu.  Add  NHiCl  to  dissolve  any  PbSO4  which  may  have  pre- 
cipitated out,  and  make  the  solution  up  to  1  liter.  Concentrate 
a  500  cc.  aliquot  of  this  solution  to  about  300  cc.  (all  H2O2  must 
be  expelled  from  the  solution) ;  transfer  to  a  400  cc.  beaker  and 
precipitate  the  Pb  as  PbCrC>4  as  directed  on  page  47  for  the 
determination  of  Total  Lead  Oxide  in  Lead  Arsenate. 

Total  Arsenic  (Official). — Proceed  as  directed  under  Total 
Arsenic  in  Paris  Green,  page  55,  using  an  amount  of  the  dry, 
powdered  sample  equal  to  the  As2Os  equivalent  of  500  cc.  of 
the  standard  iodine  solution.  The  number  of  cc.  of  the  standard 
iodine  solution  used,  divided  by  2,  represents  directly  the  per  cent 
of  total  arsenic  in  the  sample  expressed  as  As2Os. 

Water-soluble  Arsenic  Oxide  (Tentative). — Proceed  as  directed 
under  Water-soluble  Arsenic  Oxide  in  Lead  Arsenate,  page  49. 

REFERENCE. — J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis 
(1916),  pages  71,  72. 

PARIS  GREEN 

General. — Paris  Green  is  the  aceto-arsenite  of  copper.  The 
theoretical  composition  is:  As2Oa  58.55%,  CuO  31.39%,  acetic 
acid  11.84%.  The  commercial  material,  however,  always  con- 
tains more  or  less  Na2SO4,  but  in  good  samples  the  amount  should 
not  be  much  over  1%.  It  is  also  sometimes  adulterated  with 
CaSO4. 

The  following  procedures  are  the  methods  of  the  Association 
of  Official  Agricultural  Chemists: 

Preparation  of  Sample  (Tentative). — Mix  thoroughly  before 
analysis.  Make  water-soluble  arsenic  determinations  on  the 
sample  as  received  without  further  pulverizing  or  drying. 


GENERAL  INORGANIC  ANALYSES  55 

Moisture  (Tentative).— Dry  2  grams  at  105-110°  C.  for  five 
hours  and  report  the  loss  as  moisture. 

Total  Arsenic  (Official). — (Arsenic  present  as  arsenate  is 
titrated  as  As2Os.) 

(A)  REAGENTS. — (a)  Starch  Indicator. — Mix  about  0.5  gram 
of  finely  powdered  potato  starch  with  cold  water  to  a  thin  paste; 
pour  into  about  100  cc.  of  boiling  water. 

(b)  Standard  Arsenious  Oxide  Solution. — Dissolve  4  grams  of 
pure  As2O3  in  a  beaker  by  boiling  with  about  300-400  cc.  of 
water  containing  20  cc.  of  cone.  H2SO4;    cool,  transfer  to  a  liter 
graduated  flask  and  dilute  to  the  mark. 

(c)  Standard    Iodine    Solution. — Prepare    an    approximately 
0.1  N  solution  as  follows:    Mix  intimately  12.70  grams  of  pure 
iodine  with  twice  its  weight  of  pure  KI.     Dissolve  in  a  small 
amount  of  water,  filter  and  dilute  the  filtrate  to  1  liter  in  a  gra4- 
uated  flask.     Standardize  against  (6)  above  as  follows:    Pipette 
50  cc.  of  the  As2Os  solution  into  an  Erlenmeyer  flask,  dilute  to 
about  400  cc.,  neutralize  with  NaHCOs,  add  4-5  grams  in  excess, 
and  add  the  standard  iodine  solution  from  a  burette,  shaking  the 
flask  continuously,  until  the  yellow  color  disappears  slowly  from 
the  solution,  then  add  5  cc.  of  the  starch  indicator  and  continue 
adding  the  iodine  solution,  drop  by  drop,  until  a  permanent  blue 
color  is  obtained.     Calculate  the  value  of  the  standard  iodine 
solution  in  terms  of  As2Os  and  of  As2O5.     Occasionally  restandard- 
ize  the  iodine  against  freshly  prepared  As2Os  solution. 

(B)  APPARATUS. — The  apparatus   is  shown  in   Fig.  3.     The 
distillation  flask  rests  on  a  metal  gauze  which  fits  over  a  circular 
hole  in  a  heavy  sheet  of  asbestos  board.     The  first  two  Erlenmeyer 
flasks  are  of  500  and  1000  cc.  capacity  and  contain  about  40  and 
100  cc.  of  water,  respectively.     Both  of  these  flasks  should  be 
placed  in  a  pan  and  kept  surrounded  with  cracked  ice  and  water. 
The  third  flask,  containing  a  small  amount  of  water,  is  used  as  a 
trap. 

(C)  DETERMINATION. — Weigh  an  amount  of  the  sample  equal 
to  the  As2Os  equivalent  of  250  cc.  of  the  standard  iodine  solution, 
and  wash  into  the  distillation  flask  by  means  of  100  cc.  of  cone. 
HC1.     Add  5  grams  of  cuprous  chloride  and  distill. 

When  the  volume  in  the  distillation  flask  is  reduced  to  about  40 
co.,  add  50  cc.  of  cone.  HC1  by  means  of  the  dropping  funnel  and 


56  TECHNICAL  METHODS  OF  ANALYSIS 

continue  distillation  until  200  cc.  of  the  acid  distillate  have  passed 
over.  Then  wash  down  the  condenser  and  all  connecting  tubes 
carefully,  transfer  these  washings  and  contents  of  the  three  Erlen- 
meyer  flasks  to  a  liter  graduated  flask  and  dilute  to  the  mark. 
Mix  thoroughly,  pipette  400  cc.  into  an  Erlenmeyer  flask  and 
nearly  neutralize  with  a  saturated  solution  of  NaOH  or  KOH, 
using  a  few  drops  of  phenolphthalein  indicator  and  keeping  the 
solution  well  cooled. 

Continue   as   directed   under   Reagents    (c),    beginning   with 
"neutralize  with  NaHCOs."     The  number  of  cc.  of  iodine  used  in 


FIG.  3.  —  Apparatus  for  Determining  Arsenic  in  Paris  Green. 

this  titration  represents  directly  the  total  per  cent  of  arsenic  in 
the  sample,  expressed  as  As2O3. 

NOTE.  —  In  case  the  regular  0.1  N  iodine  solution  of  the  laboratory  is  used, 
the  amount  can  be  calculated  from  1  cc.  0.1  N  iodine  =  0.004948  gram 


Total  Arsenious  Oxide.  —  (The  following  methods  determine 
As,  and  Sb  if  present,  as  the  -ous  oxides,  As20a  and  Sb2Oa,  respec- 
tively. Ferrous  and  cuprous  salts  vitiate  the  results.) 

METHOD  I.  —  C.  C.  Hedges  Method,  Modified  (Tentative). 

(a)  Reagents.  —  The  reagents  and  solutions  are  the  same  as 
those  described  above  under  Total  Arsenic. 

(6)  Determination.  —  Weigh  an  amount  of  the  sample  equal  to 
the  As2Os  equivalent  of  100  cc.  of  the  standard  iodine  solution, 
wash  into  an  Erlenmeyer  flask  with  10-15  cc.  of  dil.  HC1  (1:1) 
followed  by  about  100  cc.  of  water,  and  heat  on  the  steam  bath  to 
complete  solution,  at  a  temperature  not  exceeding  60°  C.  Cool, 
neutralize  with  NaHCO3,  add  4-5  grams  in  excess,  and  then  suf- 


GENERAL  INORGANIC  ANALYSES  57 

ficient  25%  NIrLtCl  solution  to  dissolve  the  precipitated  copper. 
Dilute  somewhat  and  titrate  as  directed  under  (C)  above.  A  correc- 
tion must  be  applied  for  the  amount  of  iodine  solution  necessary  to 
produce  a  blue  color  with  starch  in  the  presence  of  copper  (using 
an  equivalent  weight  of  copper  sulfate).  The  corrected  number  of 
cc.  of  the  standard  iodine  solution  used  represents  directly  the 
per  cent  of  As2Os  in  the  sample.  ' 

METHOD  II.  C.  M.  Smith  Method,  Modified  (Tentative). — 
Proceed  as  above  using  dil.  H2&O4  (1:4)  instead  of  dil.  HC1. 
The  solution  in  this  case  may  be  heated  to  boiling. 

Sodium   Acetate-soluble   Arsenious    Oxide    (Tentative). 

(A)  REAGENTS. — (a)  Sodium  Acetate  Solution. — Prepare  a  solu- 
tion containing  12.5  grams  of  NaC2Hs02  •  3H2O  in  each  25  cc. 

The  other  reagents  are  described  under  Total  Arsenic. 

(B)  DETERMINATION. — Place  1  gram  of  the  sample  in  a  100  cc. 
flask  and  boil  for  five  minutes  with  25  cc.  of  the  sodium  acetate 
solution.     Dilute  to  the  mark,  shake,  and  pass  through  a  dry 
filter  paper.     Titrate  an  aliquot  of  this  filtrate  as  directed  under 
(C)  above.     Calculate  the  amount  of  As2Os  present  and  express 
the  result  as  per  cent  of  sodium  acetate-soluble  As20s. 

Water-soluble  Arsenious  Oxide  (Tentative). 

(A)  REAGENTS. — Same  as  for  Total  Arsenic. 

(B)  DETERMINATION. — To   1  gram  of  the  sample  in  a  liter 
Florence  flask  add  1  liter  of  recently  boiled  water  which  has  been 
cooled  to  exactly  32°  C.     Stopper  the  flask  and  place  in  a  water 
bath  kept  at  32°  C.  by  means  of  a  thermostat.     Digest  for  twenty- 
four  hours,  shaking  hourly  for  eight  hours  during  this  period.* 
Filter  through  a  dry  filter  and  titrate  250  cc.  of  the  filtrate  as 
directed  under  (C)  above.     Correct  for  the  amount  of  the  standard 
iodine  necessary  to  produce  the  same  color,  using  the  same  reagents 
and  volume.     Calculate  the  amount  of  As20s  present  and  express 
the  result  as  per  cent  of  water-soluble  As2Os. 

Total  CuO. — (A)  ELECTROLYTIC  METHOD  (OFFICIAL).— Treat 
2  grams  of  the  sample  in  a  beaker  with  100  cc.  of  water  and  about 
2  grams  of  NaOH  and  boil  thoroughly  until  all  Cu  is  precipitated 
as  Cu2O.  Filter,  wash  well  with  hot  water,  dissolve  the  precipitate 
in  hot  dil.  HNOs,  cool,  transfer  to  a  250  cc.  graduated  flask  and 
dilute  to  the  mark.  Use  50-100  cc.  of  this  solution  for  the  elec- 

*  See  note  on  page  48  under  Total  Water-soluble  Matter  in  Lead  Arsenate. 


58  TECHNICAL  METHODS  OF  ANALYSIS 

trolytic  determination  of  Cu  either  with  a  rotating  cathode  and 
stationary  anode  in  a  beaker,  or  with  a  rotating  spiral  anode, 
using  a  weighed  150  cc.  platinum  dish  for  the  cathode,  and  a  current 
of  about  3  amperes.  After  all  the  Cu  is  deposited,  wash  the 
deposit  with  water  by  siphoning,  then  rinse  with  alcohol,  dry  for  a 
few  minutes  in  an  oven,  weigh  and  calculate  to  per  cent  of  CuO. 

CALCULATION.— CuX  1.2517  -  CuO. 

(B)  THIOSULFATE  METHOD  (OFFICIAL). — Determine  Cu  in 
another  aliquot  of  the  HNOs  solution  of  Cu2O  prepared  as  de- 
scribed above,  by  titrating  with  0.1  N  thiosulfate  solution  as  fol- 
lows :  After  washing  the  precipitated  Cu2O  filtered  on  Gooch  cru- 
cible, cover  the  Gooch  with  a  watch  glass  and  dissolve  the  oxide 
with  5  cc.  of  warm  HNOs  (1  :  1)  poured  under  the  watch  glass  with 
a  pipette.  Catch  the  filtrate  in  a  250  cc.  flask,  wash  the  watch 
glass  and  Gooch  free  of  Cu,  using  about  50  cc.  of  water.  Boil  to 
expel  red  fumes,  add  5  cc.  of  bromine  water,  boil  off  the  Br,  remove 
from  the  heat  and  add  a  slight  excess  of  cone.  NH4OH  (about  7  cc. 
are  required).  Again  boil  until  the  excess  of  ammonia  is  expelled, 
as  shown  by  a  change  of  color  of  the  liquid  and  partial  precipita- 
tion. Then  add  a  slight  excess  of  80%  acetic  acid  (3  or  4  cc.) 
and  boil  for  one  minute.  Cool  to  room  temperature  and  add 
10  cc.  of  30%  KI  solution.  Titrate  at  once  with  thiosulfate 
solution  until  the  brown  tinge  has  become  weak,  then  add 
sufficient  starch  indicator  (see  reagents  under  Total  Arsenic) 
to  produce  a  marked  blue  coloration.  Continue  the  titration 
cautiously  until  the  color  due  to  free  iodine  has  entirely  vanished. 
The  blue  color  changes  toward  the  end  to  a  faint  lilac.  If  at  this 
point  the  thiosulfate  be  added  drop  by  drop  and  a  little  time 
allowed  for  complete  reaction  after  each  addition,  there  is  no 
difficulty  in  determining  the  end  point  within  a  single  drop. 
One  cc.  of  the  thiosulfate  solution  will  be  found  to  correspond 
to  about  0.0064  gram  of  Cu.  Calculate  to  per  cent  CuO. 

NOTE. — The  thiosulfate  solution  should  be  standardized  against  pure 
copper  foil.  Weigh  out  accurately  about  0.2  gram;  dissolve  in  a  250  cc. 
flask  by  warming  with  5  cc.  of  a  mixture  of  equal  parts  of  cone.  HNOs  and 
water.  Dilute  to  50  cc.,  boil  to  expel  red  fumes,  add  5  cc.  of  bromine  water 
and  proceed  as  above. 

REFERENCE. — J.    Assoc.    Official   Agr.  Chemists,     Methods   of   Analysis 
(1916),  page  63. 


GENERAL  INORGANIC  ANALYSES  59 

LIME  SULFUR  SOLUTION 

General. — Lime  sulfur  solutions  are  made  by  boiling,  either  by 
direct  heat  or  by  live  steam,  sulfur  and  freshly  slaked  lime  in  water. 
The  resulting  solution  contains  considerable  amounts  of  poly- 
sulfides  and  thiosulfate  and  very  small  amounts  of  sulfate  and  sul- 
fite.  In  commercial  practice,  1  part  of  lime  and  2  parts  of  sulfur 
are  used.  Lime  comparatively  free  from  magnesia  must  be 
employed. 

The  sample  for  analysis  should  be  kept  tightly  stoppered  and 
not  exposed  to  air,  as  it  will  very  easily  precipitate  free  sulfur. 

The  determinations  below  marked  "  Official  "  are  those  of  the 
Association  of  Official  Agricultural  Chemists. 

Specific  Gravity. — Determine  the  sp.  gr.  with  a  Westphal 
balance  at  15.5°  C.  (60°  F.)  and  calculate  to  degrees  Baume; 
or  if  there  is  sufficient  sample  at  hand,  determine  the  gravity 
directly  with  a  Baume  hydrometer. 

Total  Sulfur  (Official). — Measure  and  accurately  weigh  from  a 
stoppered  weighing  bottle  about  10  cc.  of  the  clear  sample.  Trans- 
fer to  a  250  cc.  graduated  flask,  partly  filled  with  recently  boiled 
and  cooled  distilled  water,  and  dilute  to  the  mark  with  the  same 
water.  For  the  determination  of  total  sulfur  and  for  other  deter- 
minations (unless  otherwise  directed)  use  10  cc.  aliquots  of  this 
solution. 

Transfer  a  10  cc.  aliquot  to  a  400  cc.  beaker,  add  about  3 
grams  of  Na2O2,  cover  immediately  with  a  watch  glass  and  warm 
on  the  steam  bath,  with  frequent  shaking,  until  all  S  is  oxidized 
to  sulfate,  adding  more  peroxide  if  necessary.  Dilute,  acidify 
with  HC1,  evaporate  to  dryness,  treat  with  water  acidified  with 
HC1,  boil,  and  filter  to  remove  silica,  if  present.  Dilute  the  fil- 
trate to  300  cc.,  add  50  cc.  of  cone.  HC1,  heat  to  boiling  and  pre- 
cipitate with  excess  of  10%  BaCl2  solution  slowly  and  stirring 
constantly.  (The  rate  is  best  regulated  by  attaching  a  suitable 
capillary  tip  to  a  burette  containing  the  BaCl2  solution.)  Evapo- 
rate to  dryness  on  the  steam  bath,  take  up  with  hot  water,  filter 
through  a  quantitative  filter  paper,  wash  until  free  from  Cl  and 
ignite  to  constant  weight  over  a  Bunsen  burner.  Weigh  as 
BaSO4  and  calculate  to  sulfur.  Previous  to  use,  test  all  reagents 
for  sulfur  and,  if  present,  make  corrections  accordingly. 

CALCULATION.— BaSO4X  0.1373  =  Sulfur. 


60  TECHNICAL  METHODS  OF  ANALYSIS 

Sulfur  as  Polysulfides. — Pipette  10  cc.  of  the  solution  de- 
scribed above  into  a  small  beaker  and  add  about  30  cc.  of  water. 
Then  run  into  the  solution  from  a  burette  0.1  N  HC1,  drop  by  drop, 
with  constant  stirring,  until  the  yellow  tint  has  practically  disap- 
peared. Add  2  drops  of  methyl  orange  and  continue  the  addition 
of  acid  until  the  first  permanent  pink  color  appears.  (After  stand- 
ing for  some  time  this  tint  will  gradually  disappear.)  The  solu- 
tion will  be  milky  white  from  finely  divided  S  present,  but  it 
is  not  difficult  to  ascertain  the  exact  end  point  of  the  reaction. 
Let  the  solution  stand  a  few  moments  to  permit  S  to  settle  and 
collect  together.  Filter  on  a  weighed  Gooch  crucible,  wash  thor- 
oughly, dry  at  about  40°  C.  and  weigh  directly  as  free  S.  This 
represents  S  combined  in  the  form  of  polysulfides. 

NOTES. — (1)  Precipitation  of  S  by  means  of  weak  acid  does  not  decom- 
pose thiosulfate  in  solution. 

(2)  An  optional  method  of  determining  sulfur  is  as  follows:  Filter 
on  a  small  filter  paper  instead  of  on  a  Gooch  crucible,  and  after  thoroughly 
washing,  gently  boil  the  paper  and  contents  in  50  cc.  of  10%  KOH  solution 
until  all  sulfur  is  dissolved.  After  cooling  add  50  cc.  of  a  3%  solution  of  H2O2, 
free  from  sulfates.  Heat  on  the  steam  bath  for  exactly  thirty  minutes  and 
then  acidify  with  HC1  and  precipitate  with  BaCl2  in  the  usual  manner.  Finally 
weigh  as  BaSO4.  Run  a  "blank"  on  the  KOH  solution  and  subtract  any 
sulfur  found. 

Sulfur  as  Sulfide  (Official). — Dilute  10  cc.  of  the  solution  pre- 
pared as  for  Total  Sulfur  to  about  100  cc.  and  add  ammoniacal 
ZnCU  solution  (see  notes)  until  the  sulfide  is  all  precipitated,  which 
will  be  shown  by  adding  a  drop  of  the  clear  solution  to  a  few  drops 
of  nickel  sulf ate  solution ;  if  any  sulfide  remains,  this  will  cause  a 
black  precipitate.  Filter  at  once  and  thoroughly  wash  the  pre- 
cipitate with  cold  water. 

Transfer  the  filter  paper  and  precipitate  to  a  beaker;  cover 
with  water,  disintegrate  with  a  glass  rod  and  add  about  3  grams 
of  Na2C>2,  keeping  the  beaker  well  covered  with  a  watch  glass. 
Warm  on  a  steam  bath  with  frequent  shaking  until  all  S  is  oxidized 
to  sulfate,  adding  more  Na2O2  if  necessary.  Make  slightly  acid 
with  HC1,  filter  to  remove  shreds  of  filter  paper,  wash  thoroughly 
with  hot  water  and  determine  sulfur  in  the  filtrate  exactly  as  under 
Total  Sulfur  above.  This  gives  both  monosulfide  and  polysulfide 
sulfur.  Subtract  the  polysulfide  sulfur  as  previously  determined 
and  report  the  difference  as  (mono)  sulfide  sulfur. 


GENERAL  INORGANIC  ANALYSES  61 

NOTES. — (1)  Ammoniacal  zinc  chloride  solution — Dissolve  50  grams  of 
pure  ZnCl2  in  water.  Add  sufficient  NH4OH  to  redissolve  the  precipitate 
first  formed;  then  add  50  grams  of  NH^Cl  and  dilute  to  1  liter. 

(2)  Blank  determinations  of  the  amount  of  S  in  the  reagents  used  should 
be  made  and  corrections  applied. 

(3)  The  amount  of  sulfur  as  polysulfide  is  almost  always  quite  close  to 
3.5  times  the  amount  of  sulfur  as  sulfide.     This  shows  that  the  polysulfide  in 
solution  is  not  one  compound  only,  but  probably  a  mixture  of  CaS4  and  CaS6. 

Sulfur  as  Thiosulfate  (Official). — Dilute  50  cc.  of  the  solution 
prepared  as  for  Total  Sulfur  to  about  100  cc.  in  a  250  cc.  grad- 
uated flask.  Add  ammoniacal  ZnCU  solution  until  in  slight  excess 
and  make  up  to  the  mark.  Shake  thoroughly  and  filter  through 
a  dry  filter.  To  200  cc.  of  the  filtrate  add  methyl  orange  and 
exactly  neutralize  with  0.1  N  HC1.  Titrate  this  neutral  solution 
with  0.1  N  iodine,  using  a  few  drops  of  starch  paste  as  indicator. 
From  the  amount  of  iodine  solution  required  calculate  the  sulfur 
present  as  thiosulfate. 

CALCULATION. — 1  cc.  0.1  N  iodine  =  0.0064 12  gram  sulfur. 

=  0.01581  gram  Na2S203. 

Sulfur  as  Sulfate  (Official). — To  the  solution  from  the  deter- 
mination of  thiosulfate  add  2  or  3  drops  of  HC1.  Precipitate  cold 
with  10%  BaCl2  solution  and  let  stand  in  the  cold  overnight. 
Filter,  ignite  and  weigh  as  BaSOi.  From  this  weight  calculate 
the  sulfur  and  report  as  sulfate  sulfur. 

NOTE. — In  case  any  sulfite  is  present,  the  determination  of  thiosulfate  will 
be  too  high.  As  calcium  sulfite  is  nearly  insoluble,  however,  it  will  not  be 
present  in  more  than  traces  and  the  error  from  this  cause  will  be  negligible. 
It  is  unusual  for  the  combined  sulfate  and  sulfite  to  amount  to  more  than  a 
small  fraction  of  1%. 

Total  Lime  (Official). — To  25  cc.  of  the  solution  prepared  as 
under  Total  Sulfur  add  10  cc.  of  cone.  HC1;  evaporate  to  dry- 
ness  on  the  steam  bath,  treat  with  water  and  a  little  HC1,  warm 
until  all  the  CaCl2  is  dissolved,  and  filter  from  S  and  any  8162 
that  may  be  present.  Oxidize  the  filtrate  by  boiling  with  a  little 
cone.  HNOs;  make  ammoniacal,  filter  from  Fe  and  Al  if  present; 
heat  to  boiling  and  precipitate  the  Ca  with  (NH4)2C2O4  solution. 
Filter,  wash  and  ignite  over  a  blast  lamp  to  constant  weight. 
Weigh  as  CaO.  (The  calcium  oxalate  may  be  titrated  with 
KMnO4  in  the  usual  way,  if  desired,  instead  of  igniting  it.) 

REFERENCE. — J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis 
(1916),  page  76. 


62  TECHNICAL  METHODS  OF  ANALYSIS 


CORROSIVE  SUBLIMATE  IN  MEDICATED  GAUZE 

Weigh  30  grams  of  gauze,  or  the  whole  sample  if  less  than  this, 
and  place  in  a  200  cc.  separatory  funnel;  pack  firmly,  and  add 
200  cc.  of  warm  dil.  HC1  (15  cc.  of  cone.  HC1  per  liter).  Let  the 
acid  drain  slowly  into  a  1000  cc.  beaker,  about  2  or  3  drops  per 
second.  When  completely  drained,  add  100  cc.  more  of  the  warm 
dil.  HC1,  and  continue  the  draining  operation  until  complete. 
Repeat  5  times,  so  that  the  gauze  is  washed  with  a  total  of  800  cc.  of 
acid. 

Pass  H2S  through  the  solution  for  one  hour  and  let  stand  over- 
night. Filter  through  a  tared  filter  or  Gooch  crucible.  Wash 
6  times  with  water,  and  then  3  times  with  95%  alcohol.  Stopper 
the  bottom  of  the  funnel  with  a  small  cork;  add  CS2  sufficient  to 
cover  the  precipitate  of  HgS  completely,  and  let  stand  for  0.5 
hour.  Remove  the  stopper  and  let  drain.  Wash  once  with  C$2, 
and  3  times  with  alcohol.  Dry  and  weigh. 

In  case  a  Gooch  crucible  is  usedj  set  the  crucible  in  a  beaker 
containing  CS2  sufficient  to  cover  the  precipitate.  Let  stand  0.5 
hour,  etc.  Calculate  parts  of  HgCl2  per  thousand  parts  of  gauze. 

'  WX  1.167X100 

CALCULATION.—       — ^ —      —  =  parts  HgCb  per  thousand, 

o 

where  W  —  weight  of  HgS,  and  S  =  weight  of  gauze. 

NOTE. — This  is  the  method  prescribed  by  the  U.  S.  Government  for  testing 
medicated  surgical  dressings. 

ASBESTOS  MAGNESIA  PIPE  COVERING 

General. — This  material  consists  of  long-fibered  asbestos  mixed 
with  magnesium  carbonate.  The  specifications  on  which  it  is  gen- 
erally purchased  are  as  follows : 

Long-fibered  asbestos  not  less  than  10%. 
Magnesium  carbonate  not  less  than  85%. 

The  magnesium  carbonate  is  calculated  to  the  empirical  for- 
mula Mg(OH)2-4MgCO3-5H2O. 

Since  the  asbestos  and  magnesium  carbonate  do  not  adhere 
very  strongly  to  each  other  it  is  necessary  to  use  considerable  care 


GENERAL  INORGANIC  ANALYSES  63 

in  sampling  this  material.  A  considerable  number  of  representa- 
tive lumps  should  be  taken  for  the  analysis  and  these  lumps 
should  not  be  shaken  nor  squeezed  on  account  of  danger  of  loss  of 
carbonate.  If  it  is  attempted  to  grind  up  the  whole  sample  and 
quarter  it  down,  some  magnesium  carbonate  is  very  likely  to  be 
lost. 

Asbestos. — Weigh  out  5-10  grams  into  a  beaker  and  treat  with 
excess  of  hot  dil.  acetic  acid  (1:4)  until  there  is  no  further  effer- 
vescence. Filter  off  the  asbestos  and  wash  thoroughly  with  hot 
water.  Dry  the  residue  of  asbestos  at  105°  C.,  ignite  in  a  platinum 
crucible  and  weigh  directly  as  asbestos. 

Magnesium  Carbonate. — Weigh  out  5-10  grams  into  a  beaker 
and  treat  with  excess  of  hot  dil.  HC1  until  no  further  effervescence 
occurs.  Filter  into  a  500  cc.  or  1000  cc.  graduated  flask  and  wash 
thoroughly  with  hot  water.  Cool,  and  dilute  to  the  mark. 

Pipette  an  aliquot  of  this  solution,  representing  about  0.5  gram 
of  the  original  substance,  into  a  beaker,  dilute  to  about  100  cc., 
add  a  slight  excess  of  NHiOH  and  boil.  Then  add,  without  filter- 
ing, 5  cc.  of  (NH4)2C204  solution  and  again  boil.  Let  settle  till 
clear,  and  then  filter.  If  there  is  a  considerable  amount  of  calcium 
or  of  iron  and  alumina,  dissolve  the  precipitate  in  HC1  and  repre- 
cipitate  with  NILtOH  and  (NH4)2C2O4  as  before.  Make  the 
final  filtrate  slightly  acid  and  concentrate  until  crystallization 
begins.  Then  cool  and  dilute  until  the  crystals  go  into  solution. 
Add  a  strong  excess  of  NFLt  or  Na  phosphate  and  stir  thoroughly. 
Then  add  about  one-third  the  volume  of  cone.  NELtOH.  Let 
stand  several  hours,  filter  through  a  Gooch  crucible,  ignite  slowly 
at  first  and  then  strongly  to  constant  weight  and  weigh  as  Mg2P2Oj. 
Calculate  to  magnesium  carbonate. 

CALCULATION. — 

Mg2P2O7  X  0.8724  =  Mg(OH)2  •  4MgC03  •  5H2O. 

NOTES. — (1)  Pure  asbestos  is  a  magnesium  silicate.  The  natural  product, 
however,  also  contains  more  or  less  Fe,  Al,  and  SiO2.  If  in  the  determination 
of  asbestos,  therefore,  HC1  were  used  instead  of  acetic  acid  more  of  these  con- 
stituents would  dissolve  and  the  per  cent  of  insoluble  matter  would  generally 
be  considerably  less. 

(2)  If  the  amount  of  sample  is  limited,  the  filtrate  from  the  acetic  acid 
treatment  may  be  made  up  to  volume  and  used  for  the  magnesia  determina- 
tion. In  this  case  add  25  cc.  of  10%  NH4C1  solution  before  adding  the  phos- 
phate. 


CHAPTER  III 
GENERAL  ORGANIC  ANALYSES 

NITROGEN 

General. — The  principle  of  the  determination  of  nitrogen  in 
organic  materials  and  in  fertilizers  is  its  conversion  into  NHs 
and  a  determination  of  the  amount  of  NHs  so  formed.  The  method 
to  be  employed  depends  upon  whether  or  not  nitrates  are  present. 
In  every  case  a  "  blank  "  should  be  carried  out  to  correct  for  the 
presence  of  small  amounts  of  nitrogen  in  the  reagents  employed. 
In  running  the  blank,  employ  the  same  amount  of  each  reagent 
as  is  used  in  the  determination. 

In  this  laboratory  we  have  found  the  Gunning  methods  prefer- 
able to  the  Kjeldahl  for  most  substances.  (See  general  notes  on 
page  66.) 

METHODS  TO  BE  USED  IN  THE  ABSENCE  OF  NITRATES 

Kjeldahl  Method.* — Place  0.7-3.5  grams  of  the  substance 
to  be  analyzed  (depending  upon  the  N  content)  in  a  500  cc.  pear- 
shaped  digestion  flask.  Add  approximately  0.7  gram  of  mercuric 
oxide,  f  or  its  equivalent  of  metallic  Hg,  and  20-30  cc.  of  cone. 
H2S04.  From  0.1  to  0.3  gram  of  crystallized  CuS04  may  also  be 
used  in  addition  to  the  Hg  or  in  place  of  it.  Place  the  flask  in  an 
inclined  position  and  heat  gently  below  the  boiling  point  of  the 
acid  for  five  to  fifteen  minutes,  i.e.,  until  frothing  has  ceased.  (A 
small  piece  of  paraffin  may  be  added  to  prevent  extreme  foaming.) 
Then  raise  the  heat  until  the  acid  boils  briskly  and  digest  for  four 
hours  after  the  mixture  is  colorless,  or  nearly  so.  Remove  the 

*  For  ordinary  work  0.5  N  acid  is  recommended.  For  work  in  deter- 
mining very  small  amounts  of  nitrogen  0.1  N  acid  is  recommended. 

t  If  mercuric  oxide  is  used,  it  should  be  prepared  in  the  wet  way  but  not 
from  mercuric  nitrate. 

64 


GENERAL  ORGANIC  ANALYSES  65 

flask  from  the  flame,  hold  it  upright,  and  while  still  hot  drop  in 
KMn(>4  (finely  pulverized)  in  small  quantities  until,  after  shaking, 
the  liquid  remains  green  or  purple. 

After  cooling,  dilute  with  about  200  cc.  of  distilled  water,  add  a 
few  pieces  of  granulated  zinc  or  pumice  stone  and  25  cc.  of  K2S 
solution  (40  grams  of  commercial  K2S  in  1  liter  of  water)  wijbh 
shaking.  Next  add  50  cc.  of  a  saturated  solution  of  NaOH 
(free  from  N  compounds)  or  sufficient  to  make  the  solution  strongly 
alkaline,  pouring  it  down  the  side  of  the  flask  so  that  it  does  not 
mix  at  once  with  the  acid  solution  (50  cc.  are  usually  enough). 
Connect  the  flask  with  the  condenser  before  heating,  mix  the 
contents  well  by  swirling  and  then  distill  until  all  the  NHs  has 
passed  over,  collecting  the  distillate  in  an  excess  of  standard  acid. 
As  a  general  rule,  50  cc.  of  0.1  N  HC1  or  10  cc.  of  0.5  N  will  be  suf- 
ficient. It  should  have  cochineal,  methyl  orange,  or  methyl  red  indi- 
cator (see  general  note  3)  added  to  it  before  the  distillation  starts; 
and  if  the  color  changes  before  it  is  completed,  the  determination 
should  be  repeated,  using  either  less  of  the  original  material  or 
more  of  the  standard  acid.  The  first  150  cc.  of  the  distillate  will 
generally  contain  all  the  NHs.  The  distillation  usually  requires 
forty  to  ninety  minutes.  Wash  down  the  condenser  with  distilled 
water  and  titrate  the  excess  of  standard  acid  with  0.1  N  alkali. 

In  most  cases  the  use  of  KMnCX  is  quite  unnecessary  but  it  is 
believed  that  in  exceptional  cases  it  is  required  for  complete 
oxidation  and  in  view  of  the  uncertainty  it  is  always  used.  The 
K2S  removes  all  the  Hg  from  the  solution  and  thus  prevents 
the  formation  of  mercuro-ammonium  compounds,  which  are  not 
completely  decomposed  by  the  caustic.  The  addition  of  Zn  gives 
rise  to  an  evolution  of  hydrogen  and  prevents  violent  bumping. 

Gunning  Method. — The  apparatus  used  is  the  same  as  that 
employed  in  the  Kjeldahl  method. 

Place  the  substance  to  be  analyzed  in  a  500  cc.  digestion  flask, 
using  0.7-3.5  grams  according  to  the  proportion  of  N.  Add  10 
grams  of  powdered  K2SO4  or  7.5  grams  of  dry  powdered  Na2SO4 
(use  Baker's  c.  P.  special,  free  from  nitrogen)  and  25  cc.  of  cone. 
£[2804.  Add  also  about  0.2  gram  of  crystallized  CuS04  or  0.1 
gram  of  copper  wire.  Conduct  the  digestion  exactly  as  in  the 
Kjeldahl  .process,  starting  with  a  temperature  below  boiling  point 
and  increasing  the  heat  gradually  until  frothing  ceases.  Digest 


66  TECHNICAL  METHODS  OF  ANALYSIS 

for  four  hours  after  the  mixture  is  colorless,  or  nearly  so.  Do  not 
add  either  KMnC>4  or  K2S.  Cool,  dilute,  add  an  excess  of  NaOH, 
distill  and  titrate  as  in  the  Kjeldahl  method.  In  neutralizing,  it  is 
advisable  to  add  a  few  drops  of  methyl  orange  or  litmus  indicator 
by  which  one  can  tell  when  an  excess  of  NaOH  has  been  added. 

'  NOTES. — (1)  It  is  well  for  convenience  to  use  the  same  amount  of  H2SO4 
each  time  for  digestion  and  to  determine  how  much  of  the  strong  NaOH  is 
necessary  to  neutralize  this  amount  of  acid,  marking  the  amount  on  the  bottle 
containing  the  NaOH. 

(2)  If  copper  wire  of  the  same  size  is  always  used,  it  can  easily  be  deter- 
mined how  long  a  piece  will  weigh  0.1  g.  and  then  cut  up  a  number  of  pieces 
of  the  proper  length.  The  use  of  NaaSO4  and  copper  wire  has  not  yet  been 
made  an  official  method  of  the  A.  O.  A.  C.  but  sufficient  work  has  been  done  to 
show  that  it  gives  accurate  results. 

Kjeldahl-Gunning-Arnold  Method. — Place  0.7-3.5  grams  of 
the  material  (according  to  the  N  content)  in  the  digestion  flask. 
Add  15-18  grams  of  powdered  K2S04  (or  10-12  grams  Na2SO4), 
1  gram  of  CuSO4,  1  gram  of  HgO  (or  its  equivalent  of  metallic  Hg), 
and  25  cc.  of  cone.  H2S04.  Heat  gently  until  frothing  ceases, 
then  boil  briskly  and  continue  digestion  for  at  least  two  hours 
after  oxidation  is  complete;  cool,  dilute  with  about  200  cc.  of 
water,  add  50  cc.  of  K^S  solution,  make  strongly  alkaline  with 
NaOH  solution  and  complete  the  distillation  as  under  the  Kjeldahl 
method. 

GENERAL  NOTES. — (1)  A  blank  determination  should  be  run,  using  all 
reagents  in  the  same  amount  as  in  the  regular  determination. 

(2)  We  have  found  the  Gunning  methods  the  most  convenient  for  use  but 
either  method  gives  accurate  results,  and  the  Kjeldahl  is  quicker. 

(3)  It  is  generally  recommended  that  cochineal  or  methyl  red  be  used  in 
titrating  back  the  excess  of  acid,  but  accurate  results  can  be  obtained  by  using 
methyl  orange  as  follows: 

To  a  container  of  similar  size  and  shape  to  that  containing  the  distillate, 
add  an  amount  of  distilled  water  equal  to  the  volume  of  the  distillate  and  add 
the  same  number  of  drops  of  indicator  (two  or  three  are  sufficient)  as  were 
added  to  the  standard  acid.  Then  titrate  until  the  color  matches  the  color 
of  the  distilled  water  containing  the  methyl  orange.  (The  titration  of  the 
blank  on  the  reagents  should,  of  course,  be  carried  to  the  same  end  point.) 

(4)  With  certain  materials  it  will  be  necessary  to  add  considerably  more 
H2SO4  than  the  amounts  given  above.     In  this  case,  care  must  be  taken  that 
the  mixture  in  the  flask  is  alkaline  before  the  distillation  is  started. 

(5)  Only  a  moderate  excess  of  the  NaOH  solution  should  be  added  since 
considerable  excess  often  causes  frothing. 


GENERAL  ORGANIC  ANALYSES  67 


METHODS  TO  BE  USED  IN  THE  PRESENCE  OF  NITRATES 

The  results  obtained  by  these  methods  give  total  nitrogen  and  include  the 
nitrogen  of  the  nitrates. 

Modified  Kjeldahl  Method.— Place  0.7-3.5  grams  of  the 
substance  in  a  Kjeldahl  digestion  flask:  (1)  Add  30  cc.  of  cone. 
H2SO4  containing  1  gram  of  salicylic  acid.  Shake  until  thor- 
oughly mixed,  let  stand  for  at  least  thirty  minutes  and  then  add 
5  grams  of  crystallized  sodium  thiosulfate.  Or,  (2)  add  to  the 
substance  30  cc.  of  cone.  H2S04  containing  2  grams  of  salicylic 
acid,  let  stand  at  least  thirty  minutes  and  then  add  gradually 
2  grams  of  zinc  dust,  shaking  the  contents  of  the  flask  at  the  same 
time.  The  zinc  dust  should  be  an  impalpable  powder.  Gran- 
ulated Zn  or  Zn  borings  will  not  answer. 

Place  the  flask  on  the  stand  for  holding  digestion  flasks  and 
heat  over  a  low  flame  until  all  danger  from  frothing  has  passed. 
Then  raise  the  heat  until  the  acid  boils  briskly  and  continue  boiling 
until  white  fumes  no  longer  escape  from  the  flask.  This  requires 
about  five  to  ten  minutes.  Then  add  approximately  0.7  gram 
of  HgO  or  its  equivalent  in  metallic  Hg.  Continue  the  boiling 
until  the  liquid  in  the  flask  is  colorless  or  nearly  so.  In  case  the 
contents  of  the  flask  are  likely  to  become  solid  before  this  point 
is  reached,  add  10  cc.  more  of  cone.  H2SO4.  Complete  the  oxida- 
tion with  a  little  KMnC>4  in  the  usual  way  and  proceed  with  the 
distillation  as  described  in  the  Kjeldahl  method.  A  blank  should 
be  run  on  all  the  reagents  employed. 

Modified  Gunning  Method. — In  a  500  cc.  digestion  flask 
place  0.7-3.5  grams  of  the  substance  to  be  analyzed,  add  30  cc.  of 
cone.  H2SO4  containing  1  gram  of  salicylic  acid  dissolved  in  it, 
shake  until  thoroughly  mixed  and  let  stand  for  at  least  thirty 
minutes  with  frequent  shaking.  Add  5  grams  of  sodium  thio- 
sulfate and  heat  the  solution  for  five  minutes.  Cool,  add  10  grams 
of  powdered  K2SO4  (Baker's  c.  P.  special)  and  heat  very  gently 
until  foaming  ceases  and  then  strongly  until  nearly  colorless. 
Dilute,  neutralize  and  distill  as  in  the  Gunning  method. 

Absolute  or  Cuprous  Oxide  Method. — By  this  method  the 
nitrogen  is  all  set  free  as  such  and  measured  in  an  azotometer.  It 
is  not  ordinarily  employed  in  commercial  analysis  but  is  described 


68  TECHNICAL  METHODS  OF  ANALYSIS 

in  the  Journal  of  the  Association  of  Official  Agricultural  Chemists, 
Methods  of  Analysis  (1916),  page  8. 

AMMONIACAL  NITROGEN 

MgO  Method. — Place  0.7-3.5  grams  of  the  material,  according 
to  the  NHs  content,  in  a  distillation  flask  with  about  200  cc.  of 
water  and  5  grams  or  more  of  MgO,  free  from  carbonates.  Then 
connect  the  flask  with  a  condenser  and  distill  100  cc.  of  the  liquid 
into  a  measured  quantity  of  standard  acid  and  titrate  the  excess 
of  acid  with  standard  alkali. 

NITRIC  AND  AMMONIACAL  NITROGEN 

Ulsch-Street  Method. — Place  1  gram  of  the  sample  in  a  500 
cc.  flask,  add  about  30  cc.  of  water  and  2-3  grams  of  reduced  iron 
and,  after  standing  sufficiently  long  to  insure  solution  of  the  sol- 
uble nitrates  and  ammonium  salts,  add  10  cc.  of  a  mixture  of  cone. 
H2SO4  with  an  equal  volume  of  water.  Shake  thoroughly,  place  a 
long-stemmed  funnel  in  the  neck  of  the  flask  to  prevent  mechanical 
loss  and  let  stand  for  a  short  time  until  the  violence  of  the  reaction 
has  moderated.  Heat  the  solution  slowly;  then  boil  for  five  min- 
utes and  cool.  Add  about  100  cc.  of  water,  a  little  paraffin,  and 
7-10  grams  of  MgO,  free  or  nearly  free  from  carbonates.  Connect 
with  a  condenser  such  as  is  used  in  the  Kjeldahl  method  and  boil 
the  mixture  for  forty  minutes  nearly  to  dryness,  collecting  the 
NHs  in  a  measured  quantity  of  standard  acid,  and  titrate  the 
excess  with  standard  alkali  in  the  usual  way.  The  nitrogen  ob- 
tained represents  the  nitrates  plus  the  ammonium  salts  contained 
in  the  sample. 

In  the  analysis  of  nitrate  salts  proceed  as  above,  except  that 
25  cc.  of  the  nitrate  solution  (equivalent  to  0.25  gram  of  the 
sample)  are  employed  with  5  grams  of  reduced  iron.  After  boiling, 
add  75  cc.  of  water  and  an  excess  of  NaOH  solution  and  complete 
the  determination  as  above. 

Zinc-Iron  Method. — Dissolve  10  grams  of  the  sample  in 
water  and  dilute  to  500  cc.  Place  25  cc.  of  this  solution,  corre- 
sponding to  0.5  gram  of  the  substance,  in  a  400  cc.  distillation  flask. 
Add  120  cc.  of  water,  5  grams  of  well-washed  and  dried  zinc  dust, 


GENERAL  ORGANIC  ANALYSES  69 

and  5  grams  of  reduced  iron.  To  the  solution  add  80  cc.  of  sat- 
urated NaOH  solution,  connect  the  flask  with  the  condenser  and 
conduct  the  distillation  simultaneously  with  the  reduction,  col- 
lecting the  NHa  in  excess  of  standard  acid.  Continue  the  dis- 
tillation until  100  cc.  have  been  distilled  and  titrate  the  excess  acid 
with  standard  alkali. 


NITROGEN  IN  NITRATES 

Ferrous  Sulfate-Zinc-Soda  Method  (Tentative). — Place  0.5 
gram  of  the  nitrate  salt  in  a  600-700  cc.  flask,  add  200  cc.  of  water, 
5  grams  of  powdered  zinc,  1-2  grams  of  ferrous  sulfate  and  50  cc. 
of  30%  NaOH  solution.  Connect  with  the  distilling  apparatus 
and  distill,  collecting  the  distillate  in  the  usual  way  in  0.1  N  acid 
and  titrating  the  excess  with  standard  alkali. 


METHODS  FOR  "AVAILABLE  ORGANIC  NITROGEN" 

Organic  Nitrogen  Soluble  in  Neutral  Permanganate. — As 
a  preliminary  test  for  the  determination  of  water-insoluble  organic 
N,  place  1  gram  of  the  material  on  an  11  cm.  filter  paper  and  wash 
with  water  at  room  temperature  until  the  filtrate  measures  250  cc. 
Dry  and  determine  the  N  in  the  residue  by  the  Kjeldahl  or  Gun- 
ning method,  making  a  correction  for  the  N  of  the  filter  if  necessary. 

Place  a  quantity  of  the  material  equivalent  to  0.050  gram  of 
water-insoluble  organic  N  as  determined  above  on  a  moistened 
11  cm.  filter  paper  and  wash  with  water  at  room  temperature 
until  the  filtrate  measures  250  cc.  Transfer  the  insoluble  residue 
with  25  cc.  of  tepid  water  to  a  300  cc.  Griffin  low-form  beaker. 
Add  1  gram  of  Na2CO3;  mix  and  add  100  cc.  of  2%  KMnO4  solu- 
tion; cover  with  a  watch  glass  and  immerse  for  thirty  minutes 
in  a  steam  or  hot-water  bath,  keeping  the  level  of  the  liquid  in  the 
beaker  below  that  of  the  water  in  the  bath.  Stir  twice  at  inter- 
vals of  ten  minutes.  At  the  end  of  the  digestion,  remove  from  the 
bath,  add  immediately  100  cc.  of  cold  water  and  filter  through  a 
heavy  15  cm.  folded  filter.  Wash  with  small  quantities  of  cold 
water  until  the  filtrate  measures  about  400  cc.  Determine  N 
in  the  residue  and  filter  paper  by  the  Kjeldahl  or  Gunning  method, 


70  TECHNICAL  METHODS  OF  ANALYSIS 

correcting  for  N  contained  in  the  paper.  The  N  thus  obtained  is 
the  inactive  water-soluble  organic  N.  Subtract  this  result  from 
the  total  water-insoluble  organic  N  to  obtain  the  percentage  of 
organic  N  soluble  in  neutral  permanganate. 

Organic    Nitrogen    Soluble    in    Alkaline     Permanganate.*— 

(A)  PKEPARATION  OF  SAMPLE. — /.  Mixed  Fertilizers. — Place  an 
amount  equivalent  to  0.050  gram  of  water-insoluble  organic  N 
determined  as  above  on  a  filter  paper  and  wash  with  water  at 
room  temperature  until  the  filtrate  measures  250  cc. 

II.  Raw  Materials. — Place  an  amount  of  material  equivalent 
to  0.050  gram  of  water-insoluble  organic  N,  determined  as  above, 
in  a  small  mortar.  Add  about  2  grams  of  powdered  rock  phos- 
phate, mix  thoroughly,  transfer  to  a  filter  paper  and  wash  with 
water  at  room  temperature  until  the  filtrate  measures  250  cc. 
When  much  fat  or  oil  is  present,  it  is  well  to  wash  with  ether  before 
extracting  with  water. 

(B)  DETERMINATION. — Dry  the  residue  from  the  water  extract 
above  at  a  temperature  not  exceeding  80°  C.  and  transfer  from  the 
filter  to  a  500-600  cc.  Kjeldahl  distilling  flask.    Add  20  cc.  of  water, 
15-20  small  glass  beads  or  fragments  of  pumice  stone,  a  piece  of 
paraffin  the  size  of  a  pea  and  100  cc.  of  alkaline  permanganate 
solution  (25  grams    of  pure  KMnCX  and    150    grams  of  NaOH 
separately  dissolved  in  water,  the  solutions  cooled,  mixed  and  made 
to  a  volume  of  1  liter).     Connect  with  an  upright  condenser,  to 
the  lower. end  of  which  a  receiver  containing  standard  acid  has 
been  attached.     Digest  slowly  for  at  least  thirty  minutes  below  the 
distillation  point  with  a  very  low  flame,  using  coarse  wire  gauze 
and  asbestos  paper  between  the  flask  and  flame.     Gradually  raise 
the  temperature  and  after  any  danger  from  frothing  has  passed, 
distill  until  95  cc.  of  the  distillate  are  obtained,  and  titrate  as  usual. 
When  a  tendency  to  froth  is  noticed,  lengthen  the  digestion  period 
and  no  trouble  will  be  experienced  when  the  distillation  is  begun. 
During  the  digestion  gently  rotate  the  flask  occasionally,  particu- 
larly if  the  material  shows  a  tendency  to  adhere  to  the  sides.     The 
N  thus  obtained  is  the  active  water-insoluble  organic  N. 

CALCULATIONS. — The  following  factors  will  be  found  useful  in 
calculating: 

*  This  is  not  applicable  to  fertilizers  containing  cottonseed  meal  or  castor 
pomace. 


GENERAL  ORGANIC  ANALYSES  71 

1  cc.  of  0.1  N  acid  =  0.001401  gram  N. 

=  0.001703  gram  NH3. 

=  0.01011    gram  KNO3. 

=  0.002604  gram  (NH4)20. 

=  0.008937  gram  casein  (NX 6.38). 

=  0.007844  gram  glue  (NX 5.6). 

=  0.008755  gram  protein  (NX 6.25). 

=  0.007985  gram  protein  (NX5.7).* 

REFERENCES. — The  above  methods  are  all  official  methods  of  the  Associa- 
tion of  Official  Agricultural  Chemists  unless  otherwise  indicated,  except  the 
Zinc-Ferrous  Sulfate-Soda  method  for  Nitrates,  which  is  tentative.  See 
Journal  of  Association  of  Official  Agricultural  Chemists,  Methods  of  Analysis 
(1916),  pages  5-12.  See  also  Journal  of  American  Leather  Chemists'  Asso- 
ciation 11,  454  (1916). 


METHYL  ALCOHOL 

General. — This  method  applies  to  the  analysis  of  methyl 
alcohol  to  be  used  for  denaturing  ethyl  alcohol. 

The  methyl  alcohol  submitted  must  be  partially  purified  wood 
alcohol  obtained  by  the  destructive  distillation  of  wood.  It 
must  conform  to  the  following  analytical  requirements: 

Color. — It  shall  not  be  darker  .than  the  color  produced  by  a 
freshly  prepared  solution  of  2  cc.  of  0.1  N  iodine  diluted  to  1000  cc. 
with  distilled  water. 

Specific  Gravity. — It  must  have  a  sp.  gr.  of  not  more  than  0.830 
at  60°  F.  (15.56°  C.),  corresponding  to  91°  of  Tralles'  Scale. 

Boiling  Point. — 100  cc.  slowly  heated  in  a  flask  under  conditions 
as  described  below  must  give  a  distillate  of  not  less  than  90  cc. 
at  a  temperature  not  exceeding  75°  C.  at  normal  barometric  pres- 
sure (760  mm.). 

100  cc.  of  wood  spirit  are  run  into  a  short-necked  copper  flask 
of  about  180-200  cc.  capacity  and  the  flask  placed  on  an  asbestos 
plate  having  a  circular  opening  of  30  mm.  diameter.  In  the  neck 
of  this  flask  is  fitted  a  fractionating  tube  12  mm.  wide  and  170  mm. 
long,  with  a  bulb  just  1  cm.  below  the  side  tube,  which  is  con- 
nected with  a  Liebig's  condenser  having  a  water  jacket  not  less 
than  400  mm.  long.  In  the  upper  opening  of  the  fractionating 
*  In  wheat  products. 


72  TECHNICAL   METHODS  OF  ANALYSIS 

tube  is  placed  a  standardized  thermometer,  so  adjusted  that 
its  mercury  bulb  comes  in  the  center  of  the  bulb.  The  distillation 
is  conducted  in  such  a  manner  that  5  cc.  pass  over  in  one  minute. 
The  distillate  is  run  into  a  graduated  cylinder,  and  when  the  tem- 
perature of  75°  C.  has  been  reached  at  the  normal  barometric 
pressure  of  760  mm.  at  least  90  cc.  shall  have  been  collected. 

Should  the  barometer  vary  from  760  mm.  during  the  distilla- 
tion, 1°  C.  shall  be  allowed  for  every  variation  of  30  mm.  For 
example,  at  770  mm.  90  cc.  should  have  distilled  at  75.3°  C.  and 
at  750  mm.  90  cc.  should  have  distilled  at  74.7°  C. 

Miscibility  with  Water. — It  must  give  a  clear  or  only  slightly 
opalescent  solution  when  mixed  with  twice  its  volume  of  water. 

Acetone  Content. — It  must  contain  not  more  than  20  nor  less 
than  10  grams  per  100  cc.  of  acetone  and  other  substances  esti- 
mated as  acetone  when  tested  by  the  following  (Messinger) 
method : 

With  a  standardized  pipette  measure  10  cc.  of  the  sample  into 
a  500  cc.  glass-stoppered  flask  and  make  up  to  the  mark  with  dis- 
tilled water.  Pipette  out  5  cc.  of  this  solution  (with  standardized 
pipette)  and  treat  with  10  cc.  of  2  N  NaOH  solution.  Then  add 
with  shaking  50  cc.  of  0.1  N  iodine  solution  and  make  the  mixture 
acid  with  dil.  H2S04  three  minutes  after  the  addition  of  the  iodine. 
Titrate  back  the  excess  of  iodine  with  0.1  N  sodium  thiosulfate 
solution,  using  a  few  drops  of  starch  solution  as  indicator.  From 
10.3  to  20.7  cc.  of  0.1  N  iodine  solution  should  be  used  by  the  spirit. 

IMPORTANT. — The  solution  must  be  kept  at  a  temperature 
between  15°  and  20°  C. 

CALCULATION. — Let  X  =  grams  of  acetone  in  100    cc.  of  spirit, 
Y  =  number  of  cc.  of  0. 1  N  iodine  solution 

required, 
and  N  =  volume  of  spirit  taken  for  titration  ; 

7X0.096672 
then,  X  =  -    — .* 

Blank  Correction.— -T.  D.  2268  (Dec.  4,  1915)  recommends  that 
a  blank  correction  be  made  as  follows : 

*  This  is  the  figure  given  in  Regulations  No.  30,  Revised,  United  States 
Internal  Revenue.  Using  1920  atomic  weights  the  figure  becomes  0.096772. 


GENERAL  ORGANIC  ANALYSES  73 

Weigh  accurately  from  a  weighing  bottle  about  16  grams  of 
Kahlbaum's  c.  P.  acetone  into  a  standardized  100  cc.  graduated 
flask  partially  filled  with  Kahlbaum's  c.  P.  methyl  alcohol.  Make 
up  accurately  to  the  mark  with  more  of  the  methyl  alcohol. 
Determine  the  amount  of  acetone  in  this  solution,  following  the 
method  above  described.  If  less  acetone  is  found  than  was  added, 
add  the  difference  as  the  blank  correction  to  the  acetone  found  in 
the  sample  of  denaturant.  If  more  acetone  is  found  in  the  blank 
subtract  the  difference  from  that  found  in  the  denaturant.  Sep- 
arate blanks  should  be  run  with  each  sample  of  denaturant,  taking 
care  that  all  the  conditions  are  kept  the  same. 

Esters. — It  should  contain  not  more  than  5  grams  of  esters  per 
100  cc.  of  spirit,  calculated  as  methyl  acetate  and  determined  as 
follows : 

Five  cc.  of  wood  spirit  are  run  into  a  flask  and  10  cc.  of  N 
NaOH  free  from  carbonates  are  added,  the  flask  connected  with  a 
return  condenser  and  boiled  for  two  hours.  Instead  of  digesting 
at  boiling  temperature  the  flask  may  be  allowed  to  stand  over- 
night at  room  temperature  and  then  heated  on  a  steam  bath  for 
thirty  minutes  with  an  ordinary  tube  condenser.  The  liquid 
after  digestion  is  cooled  and  the  excess  NaOH  titrated  with  N 
H2SO4  and  phenolphthalein. 

CALCULATION. — Methyl  acetate  (grams  per  100  cc.  of  spirit) 

_  0.074  Xcc.  of  N  NaOH  consumed  X 100 
cc.  spirit  taken 

=  1.48 Xcc.  of  N  NaOH  consumed. 

Bromine  Absorption. — It  must  contain  a  sufficient  quantity  of 
impurities  derived  from  the  wood  so  that  not  more  than  25  cc. 
nor  less  than  15  cc.  shall  be  required  to  decolorize  a  standard 
solution  containing  0.5  gram  of  bromine,  as  follows: 

The  standard  Br  solution  is  made  by  dissolving  12.406  grams 
of  KBr  and  3.481  grams  of  KBrOs  (which  is  of  tested  purity  and 
has  been  dried  for  two  hours  at  100°  C.)  in  a  liter  of  water.  50 
cc.  of  the  standard  solution,  containing  0.5  gram  of  Br,  are  placed 
in  a  glass-stoppered  flask  having  a  capacity  of  about  200  cc.  This 
is  acidified  with  10  cc.  of  H2SO4  (1  :  4),  the  whole  shaken  and 
allowed  to  stand  a  few  minutes.  The  wood  alcohol  is  then 


74  TECHNICAL  METHODS  OF  ANALYSIS 

allowed  to  flow  slowly  into  the  mixture,  drop  by  drop,  from  a 
burette  until  the  color  is  entirely  discharged.  The  rate  of  flow 
through  the  burette  shall  not  exceed  5  cc.  per  minute.  The  tem- 
perature of  the  mixture  should  be  20°  C. 

In  addition  to  the  above  requirements  the  methyl  alcohol 
must  be  of  such  a  character  as  to  render  the  ethyl  alcohol  with 
which  it  is  mixed  unfit  for  use  as  a  beverage. 

REFERENCES. — Regulations  No.  30  Revised,  United  States  Internal 
Revenue,  July  15,  1907.  See  also,  T.  D.  2779. 


GRAIN  ALCOHOL  OR  COLOGNE  SPIRITS 

General. — The  sample  should  be  clear  and  colorless  and  have 
the  characteristic  odor  of  ethyl  alcohol.  Medicinal  alcohol  should 
pass  all  the  qualitative  tests  of  the  U.  S.  Pharmacopoeia. 

Specific  Gravity. — Determine  the  sp.  gr.  at  60°  F.  with  a  West- 
phal  balance  or  with  a  pycnometer.  The  temperature  must  be 
exactly  60°  F.  (15.56° -C.). 

Ethyl  Alcohol. — Calculate  the  per  cent  of  ethyl  alcohol  both  by 
volume  and  by  weight  from  the  sp.  gr.  The  tables  for  these  cal- 
culations wilL  be  found  in  Leach's  Food  Inspection  and  Analysis 
(3d  edition),  pages  661-374  (4th  edition),  pages  690-703;  also  in 
Van  Nostrand's  Chemical  Annual. 

Proof. — To  obtain  the  proof  multiply  by  2  the  per  cent  of 
ethyl  alcohol  by  volume. 

Non-volatile  Residue. — Evaporate  100  cc.  in  a  weighed  plat- 
inum dish  nearly  to  dryness  on  the  water  bath,  then  transfer  to  a 
water  oven  and  dry  at  the  temperature  of  boiling  water  for  2.5 
hours.  Cool  in  desiccator  and  weigh.  To  obtain  the  per- 
centage of  non-volatile  residue  divide  the  weight  obtained  by  the 
sp.  gr.  of  the  sample. 

Acidity,  Calculated  as  Acetic  Acid. — Titrate  100  cc.  of  the 
sample  with  0.1  N  alkali  and  phenolphthalein,  until  a  permanent 
pink  color  is  formed. 

CALCULATION. — 1  cc.  0.1  N  alkali  =  0.0060  gram  acetic  acid. 

Esters,  Calculated  as  Ethyl  Acetate.— Dilute  250  cc.  of  the 
sample  with  30  cc.  of  water  and  distill  slowly  into  a  graduated 
250  cc.  flask  until  nearly  filled  to  the  mark.  Make  up  to  volume 


GENERAL  ORGANIC  ANALYSES  75 

with  water.  Shake  and  mix  thoroughly  and  use  aliquot  portions 
of  this  solution  (solution  A)  for  the  determination  of  esters,  alde- 
hydes and  furfural. 

Pipette  50  cc.  of  solution  A  into  a  300  cc.  Erlenmeyer  flask 
and  exactly  neutralize  with  0.1  N  alkali  and  phenolphthalein. 
Then  add  25-50  cc.  excess  of  the  0.1  N  alkali,  accurately  measured. 
Either  boil  for  one  hour  with  a  reflux  condenser  or  let  stand  over- 
night in  the  stoppered  flask  and  heat  with  a  reflux  condenser  for 
one-half  hour  below  the  boiling  point.  Cool,  and  titrate  with 
0.1  N  acid  and  phenolphthalein.  Multiply  the  number  of  cc.  of 
0.1  N  alkali  consumed  in  the  saponification  by  0.0088.  The 
result  is  the  weight  in  grams  of  the  esters  calculated  as  ethyl 
acetate.  Divide  this  weight  by  the  sp.  gr.  of  the  sample  and  mul- 
tiply by  2  to  obtain  the  percentage. 

Aldehydes  (Qualitative  AgNO3  Test.) — Make  up  a  solution  of 
the  following:  3  grams  c.  P.  AgNOs,  3  grams  c.  P.  NaOH,  20  cc. 
cone.  NH4OH. 

Dissolve  the  AgNOs  in  a  little  water  in  a  100  cc.  flask,  add  the 
NELtOH  and  then  the  NaOH  and  then  make  up  to  100  cc.  Dilute 
10  cc.  of  the  sample  with  10  cc.  of  water  and  place  in  a  glass-stop- 
pered bottle,  adding  1  cc.  of  the  above  alkaline  AgNOs  solution. 
Let  stand  for  one  hour  in  the  dark  and  filter  immediately.  Test 
the  filtrate  for  Ag  by  adding  an  excess  of  HNOs  and  then  a  few 
drops  of  HC1.  If  this  produces  a  precipitate  of  AgCl  (showing 
unreduced  Ag  salts),  the  alcohol  contains  less  than  the  maximum 
allowable  amount  of  aldehyde. 

NOTE. — This  test  is  copied  from  Government  specification,  January  20, 
1907. 

Aldehydes  (Quantitative). — SOLUTIONS  REQUIRED — (a)  Alco- 
hol Free  from  Aldehydes. — Place  1500  cc.  of  ordinary  95%  alcohol  in 
a  2  liter  distilling  flask,  add  about  25  grams  of  NaOH  (or  KOH) 
and  distill  down  to  about  100  cc.  Add  to  the  distillate  2.5  grams  of 
meta-phenylenediamine  hydrochloride,  stopper  and  let  stand  for 
several  days  (or  place  on  the  steam  bath  in  a  large  flask  and  reflux 
for  several  hours).  Then  distill  slowly,  rejecting  the  first  100  cc.  and 
the  last  200  cc. 

(6)  Sulfite-Fuchsin  Solution. — Dissolve  0.50  gram  of  pure 
fuchsin  in  500  cc.  of  water,  then  add  5  grams  of  SO2  dissolved 


76  TECHNICAL  METHODS  OF  ANALYSIS 

in  water.*  Make  up  to  a  liter  and  let  stand  until  colorless.  Pre- 
pare the  solution  in  small  quantities  as  it  retains  its  strength  for 
only  a  few  days. 

(c)  Standard  Acetaldehyde  Solution. — Grind  about  5  grams  of 
aldehyde  ammonia  in  a  mortar  with  ether  and  decant  the  ether. 
Repeat  this  operation  several  times,  then  dry  the  purified  salt  in  a 
current  of  air  and  finally  in  a  vacuum  desiccator  over  H2SO4. 
Weigh  out  1.386  grams  of  this  purified  aldehyde  ammonia  and  dis- 
solve in  50  cc.  of  95%  alcohol.  To  this  add  22.7  cc.  of  N  alcoholic 
H2S04  (a  solution  of  95%  alcohol  containing  49.04  grams  of  H2SO4 
per  liter).  Then  make  up  to  100  cc.  with  95  per  cent  alcohol  and 
add  0.8  cc.  extra  to  compensate  for  the  volume  of  (NEL^SCU 
precipitated.  Let  this  stand  overnight  and  filter.  This  solu- 
tion contains  1  gram  of  acetaldehyde  in  100  cc.  and  will  retain  its 
strength. 

The  standard  found  most  convenient  for  use  is  2  cc.  of  this 
strong  aldehyde  solution  diluted  to  100  cc.  with  50%  alcohol  (by 
volume).  One  cc.  of  this  solution  =  0.0002  gram  of  acetaldehyde. 
This  solution  should  be  made  up  fresh,  as  it  loses  its  strength  in  a 
day  or  two. 

PROCEDURE. — Determine  the  aldehyde  in  solution  A  as  follows: 

Dilute  10  cc.  to  50  cc.  with  aldehyde-free  alcohol  (50%  by  vol- 
ume). Add  25  cc.  of  the  fuchsin  solution  and  let  stand  fifteen 
minutes  at  15°  C.  The  solutions  and  the  reagents  should  all  be 
at  15°  C.  before  they  are  mixed.  Compare  standards  of  known 
strength  (prepared  from  the  standard  acetaldehyde  solution)  in 
the  same  way  and  match  them  colorimetrically  with  the  sample. 
Calculate  the  percentage  of  aldehydes  in  the  original  sample 
(10  cc.  of  Solution  A  =  10  cc.  of  original  sample). 

Furfural. — Dilute  20  cc.  of  solution  A  to  50  cc.  with  furfural- 
free  alcohol  (50%  by  volume).  To  this  add  2  cc.  of  colorless 
aniline  and  0.5  cc.  of  dil.  HC1  (5  :  4)  and  keep  for  fifteen  minutes 
in  a  water  bath  at  about  15°  C.  Prepare  standards  of  known 
strength  from  the  standard  furfural  solution  in  the  same  way  and 
match  up  the  colors.  Calculate  the  weight  of  furfural  in  the 
original  sample. 

*  Saturate  a  liter  of  distilled  water  with  SO2  gas.  Titrate  an  aliquot  with 
0.1  N  iodine  and  calculate  the  amount  of  SO2  in  1  cc.  of  the  solution.  Then 
measure  out  a  sufficient  number  of  cc.  to  contain  5  grams  of 


GENERAL  ORGANIC  ANALYSES  77 

Standard  Furfural  Solutions. — Dissolve  1  gram  of  freshly 
redistilled  furfural  in  100  cc.  of  95%  alcohol.  This  strong  solution 
will  keep.  Make  standards  by  diluting  1  cc.  of  this  solution  to 
100  cc.  with  50%  alcohol  (by  volume).  One  cc.  of  this  weak 
solution  =  0.0001  gram  furfural. 

Fusel  Oil. — Dilute  50  cc.  of  the  original  sample  with  50  cc.  of 
distilled  water  in  a  300  cc.  Erlenmeyer  flask.  Add  20  cc.  of  0.5  N 
NaOH  and  saponify  the  mixture  by  boiling  for  one  hour  under  a 
reflux  condenser.  (The  same  result  will  be  obtained  by  letting  the 
mixture  stand  at  room  temperature  overnight.)  Connect  the  flask 
to  a  condenser  and  distill  over  90  cc.,  then  add  25  cc.  of  water  to 
the  flask  and  continue  the  distillation  until  a  total  of  115  cc.  has 
been  collected.  Nearly  saturate  the  distillate  with  finely  ground 
salt  (NaCl)  and  add  a  saturated  solution  of  salt  until  the  sp.  gr. 
is  1.10.  Extract  this  salt  solution  four  times  with  CCU,*  using 
40,  30,  20,  and  10  cc.,  respectively.  To  the  CCU  extract  con- 
tained in  the  separatory  funnel  add  10  cc.  of  KOH  solution  (1  :  1). 
Cool  the  mixture  in  ice  water  to  approximately  0°  C.  Similarly 
cool  100  cc.  of  a  solution  of  KMnO4  (20  grams  per  liter)  accurately 
measured  in  a  flask.  To  the  contents  of  the  separatory  funnel 
add  the  bulk  of  the  KMnC>4  solution,  but  without  rinsing,  retaining 
the  residue  to  be  added  at  a  later  stage.  Remove  the  mixture 
from  the  bath  and  shake  vigorously  for  five  minutes.  Set  aside 
for  thirty  minutes  with  occasional  shaking,  letting  the  mixture 
warm  up  to  room  temperature  (20-25°  C.). 

Accurately  measure  into  a  liter  Erlenmeyer  flask  100  cc.  of  a 
solution  of  H202  about  2%  stronger  than  .the  permanganate  solu- 
tion, acidulate  with  100  cc.  of  an  approximately  25%  H2SO4 
solution  and  slowly  add  the  contents  of  the  separatory  funnel, 
with  constant  shaking,  keeping  the  acid  solution  constantly  in 
excess.  Rinse  the  separatory  funnel  and  the  flask  containing 
the  residue  of  KMnC>4  with  water,  and  add  to  the  peroxide  solu- 
tion. Finally  titrate  the  excess  of  H202  with  a  standard  KMnC>4 
solution  (10  grams  to  the  liter). 

Run  a  "  blank  "  determination  using  the  same  amounts  of 
the  stronger  KMnO4,  KOH,  H2O2,  and  H2S04  solutions,  and 

*  Purify  a  liter  of  ordinary  CC14  by  boiling  for  several  hours  under  a  reflux 
condenser  with  40  cc.  of  cone.  H2SO4  and  5  grams  K2Cr2O7  in  40  cc.  of  water. 
Distill  off  the  CC14  and  then  redistill  over  BaCO3. 


78  TECHNICAL  METHODS  OF  ANALYSIS 


titrate  the  residual  EbCb  with  the  standard  KMnCU,  as 
before. 

Subtract  the  "  blank  "  titration  from  the  first  tit  ration  and 
calculate  the  weight  of  amyl  alcohol  corresponding  to  the  differ- 
ence. Standardize  the  weaker  KMn04  solution  carefully  against 
oxalic  acid  of  normal  strength.  If  the  solution  contains  exactly 
10  grams  of  KMnO4  per  liter  as  determined  by  the  titration, 
then  each  cc.  =  0.696  gram  of  amyl  alcohol. 

Methyl  Alcohol  (Wood  Spirit).—  (A)  RICHE  AND  BARDY 
METHOD.*  —  This  method  for  the  detection  of  methyl  alcohol 
in  commercial  spirit  of  wine  depends  on  the  formation  of 
methylaniline  violet.  The  procedure  is  described  on  page  462. 

(B)  OXIDATION  METHOD.  —  Dilute  20  cc.  of  the  sample  to 
100  cc.  and  place  in  a  200  cc.  distilling  flask.  Add  from  5-8 
grams  of  chromic  acid  (CrOa)  to  oxidize  the  methyl  alcohol  to 
formaldehyde.  Distill,  collect  10  cc.  of  the  distillate,  and  test  for 
formaldehyde  by  one  of  the  following  methods: 

(1)  Hehner's  Method.  —  To  the  distillate  obtained  above  add 
100  cc.  of  fresh  milk  and  mix.     Fill  a  test  tube  about  one-third  full 
of  the  mixture  and  pour  cone.  H2S04  carefully  down  the  side,  not 
allowing  the  two  to  mix.     A  violet  or  blue  color  at  the  junction  of 
the  two  liquids  indicates  formaldehyde.     This  test  is  sensitive  to 
about  1  part  in  10,000  of  the  liquid  tested. 

(2)  Leach's  Method.  —  Mix  the  distillate  above  described  with 
an  equal  volume  of  pure  milk  in  a  porcelain  casserole  and  add  about 
10  cc.  of  cone.  HC1  containing  about  1  cc.  of  10%  FeCla  solution 
to  each  500  cc.  of  acid:     Heat  to  80-90°  C.  directly  over  the  gas 
flame,  giving  the  casserole  a  rotary  motion  to  break  up  clots.     A 
violet  color  indicates  formaldehyde. 

(3)  Morphine-Sulfate  Test.  —  Dissolve  0.5  gram  of  morphine- 
sulfate  in  500  cc.  of  cone.  H^SCU.     Place  about  5  cc.  of  this  solu- 
tion in  a  test  tube  and  add  1-2  cc.  of  the  distillate  above  referred 
to.     A  violet  color  on  standing  shows  formaldehyde. 

NOTE.  —  A  blank  test  should  always  be  carried  out  simultaneously  with 
pure  ethyl  alcohol  and  with  ethyl  alcohol  to  which  is  added  a  little  methyl 
alcohol. 

*  Tentative  method  of  Assoc.  Official  Agri'.  Chemists,  see  its  Journal, 
Methods  of  Analysis  (1916),  page  246. 


GENERAL  ORGANIC  ANALYSES  79 

Nitrates. — Neutralize  50  cc.  of  the  sample  with  0.1  N  alkali 
(phenolphthalein)  and  evaporate  nearly  to  dryness.  Take  up 
with  a  little  distilled  water  and  add  1  cc.  of  phenoldisulfonic  acid; 
then  make  alkaline  with  NILiOH.  A  bright  orange  yellow  color 
indicates  the  presence  of  nitrates.  A  "  blank  "  should  be  run  at 
the  same  time,  evaporating  50  cc.  of  distilled  water  to  make 
sure  that  no  nitrate  fumes  have  been  picked  up  during  the  evap- 
oration. 

Sulfur  Compounds. — Place  100  cc.  of  the  sample  in  a  platinum 
dish  and  make  slightly  alkaline  with  0.1  N  NaOH  (phenolphtha- 
lein). Add  5  cc.  of  H2O2,  evaporate  to  dryness  and  ignite  over 
an  alcohol  lamp.  Dissolve  the  residue  in  50  cc.  of  water,  add  5  cc. 
of  dil.  HC1,  bring  to  boiling  and  add  5  cc.  of  10%  BaC^  solution. 
If  any  precipitate  forms,  filter  it  out,  ignite  and  weigh  in  the  usual 
manner.  Calculate  to  sulfur. 

CALCULATION.— BaS04  X  0.1373  =  8. 

NOTE. — A  "blank"  should  be  run  at  the  same  time,  using  the  same 
amounts  of  each  reagent  as  was  used  in  the  determination.  If  the  blank 
shows  any  sulfur,  its  amount  should  be  determined  and  subtracted  from  the 
weight  previously  found. 

REFERENCES. — U.  S.  Dept.  of  Agriculture,  Bureau  of  Chem.,  Cir.  No.  74, 
p.  5;  U.  S.  Dept.  of  Agriculture,  Bureau  of  Chem.,  Bull.  107,  revised,  p.  185; 
Leach:  ''Food  Inspection  and  Analysis,"  3d  edition,  pp.  745-750;  U.  S. 
Pharmacopoeia,  9th  edition,  p.  35. 

FORMALDEHYDE  SOLUTION 

General. — Formaldehyde  is  a  gaseous  substance  of  the  formula 
HCHO.  It  is  used  in  aqueous  solution  as  a  disinfectant,  insecti- 
cide and  deodorizer.  The  U.  S.  P.  solution  should  contain  not 
less  than  37%  by  weight  of  HCHO.  The  solution  also  generally 
contains  more  or  less  methyl  alcohol  to  prevent  polymerization. 

The  following  procedures  for  the  determination  of  formalde- 
hyde are  recognized  as  official  methods  by  the  Association  of 
Official  Agricultural  Chemists. 

Hydrogen  Peroxide  Method. — (A)  REAGENTS. — (a)  Normal 
04. 

(b)  Normal  NaOH  (1  cc.  =  0.03002  gram  HCHO). 

(c)  Hydrogen  Peroxide:    An  approximately  3%  solution.      If 


80  TECHNICAL  METHODS  OF  ANALYSIS 

the  solution  is  acid,  neutralize  with  (fr),  using  litmus  solution  as 
indicator. 

(d)  Litmus  Solution:  A  solution  of  purified  litmus. 

(B)  DETERMINATION. — Measure  50  cc.  of  N  NaOH  into  a 
500  cc.  Erlenmeyer  flask  and  add  50  cc.  of  the  H202.  Then  add 
3  cc.  of  the  formaldehyde  solution  under  examination,  letting  the 
point  of  the  pipette  reach  nearly  to  the  liquid  in  the  flask.  Place  a 
funnel  in  the  neck  of  the  flask  and  heat  on  the  steam  bath  for  five 
minutes,  shaking  occasionally.  Remove  from  the  steam  bath, 
wash  the  funnel  with  water,  cool  the  flask  to  about  room  tempera- 
ture, and  titrate  with  N  acid,  using  litmus  solution  as  indicator. 
It  is  necessary  to  cool  the  flask  before  titration  with  the  acid  to 
get  a  sharp  end  point.  Calculate  per  cent  of  formaldehyde. 

Cyanide  Method.— (A)  REAGENTS.— (a)  0.1  N  AgN03. 

(6)  0.1  N  NH4SCN. 

(c)  KCN  solution:   Dissolve  3.1  grams  of  KCN  in  500  cc.  of 
water. 

(d)  50%  HNOS. 

(B)  DETERMINATION. — Treat  15  cc.  of  0.1  N  AgNOs  with  6 
drops  of  50%  HNOs  in  a  50  cc.  graduated  flask.  Add  10  cc.  of 
KCN  solution.  Dilute  to  volume;  shake  well;  filter  through  a  dry 
filter,  and  titrate  25  cc.  of  the  filtrate  with  0.1  N  NttiSCN,  using 
5  cc.  of  a  saturated  solution  of  ferric  alum  as  indicator,  and  con- 
tinue the  titration  until  the  first  appearance  of  a  permanent  light- 
brown  color.  Acidify  another  15  cc.  portion  of  0.1  N  AgNOs 
with  6  drops  of  50%  HN03  and  treat  with  10  cc.  of  the  KCN 
solution  to  which  has  been  added  a  measured  quantity  (the  weight 
of  which  must  be  calculated  from  the  sp.  gr.)  of  the  formaldehyde 
solution,  containing  not  over  2.5  grams  of  a  1%  solution  or  the 
equivalent.  Make  up  to  50  cc.,  filter  and  titrate  a  25  cc.  aliquot 
with  0.1  N  NILtSCN  for  the  excess  of  Ag  as  before.  The  differ- 
ence between  the  number  of  cc.  of  0.1  N  sulfocyanate  used  in  these 
2  titrations,  multiplied  by  2,  gives  the  number  of  cc.  of  0.1  N  sul- 
focyanate corresponding  to  the  KCN  consumed  by  the  formal- 
dehyde. Calculate  the  percentage  of  formaldehyde  present. 

CALCULATION.— 1  cc.  0.1  N  sulfocyanate  =  0.003002  gram 
HCHO. 

REFERENCE. — J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis 
(1916),  page  75. 


GENERAL  ORGANIC  ANALYSES  81 

FORMIC  ACID 

General. — Formic  acid  occurs  in  solutions  of  varying  strengths, 
such  as  30,  50,  75  and  90%.  The  weaker  solutions  are  generally 
made  by  diluting  the  stronger.  There  are  also  often  present  HC1 
and  H2S04,  the  amount  depending  upon  the  extent  to  which  the 
material  has  been  purified. 

Specific  Gravity  at  15.5°  C. — This  may  be  determined  by  the 
Westphal  balance;  if  great  accuracy  is  desired,  a  pycnometer 
should  be  used. 

Sulfuric  Acid. — Weigh  approximately  20  grams  from  a  weighing 
bottle  into  a  beaker.  Dilute  with  250  cc.  of  distilled  water;  add 
5  cc.  of  cone.  HC1;  heat  to  boiling,  and  add  an  excess  of  hot  10% 
BaCl2  solution.  Continue  the  boiling  for  at  least  fifteen  minutes. 
Let  stand  several  hours.  Filter  out  the  BaSCU,  wash,  ignite,  and 
weigh  in  the  usual  manner.  Calculate  to  £[2804. 

'  CALCULATION.— BaSO4  X  0.4202  =  H2S04. 

Hydrochloric  Acid. — Weigh  10-20  grams  of  the  liquid  into 
a  300  cc.  Erlenmeyer  flask.  (This  flask  should  previously  have 
been  cleaned  with  sulfuric  acid  bichromate  solution,  to  remove 
all  the  grease  and  prevent  sticking  of  the  precipitate.)  Dilute 
with  150  cc.  of  distilled  water;  add  5  cc.  cone.  HNOs  and  then 
AgNOs  solution  in  excess.  Shake  the  liquid  in  the  flask  until 
the  precipitate  settles  clearly.  Filter  through  a  weighed  Gooch 
crucible,  washing  with  cold  distilled  water.  Dry  the  precipitate 
in  the  crucible  at  100-110°  C.,  then  place  the  Gooch  crucible  in  a 
large  platinum  crucible  and  ignite  gently  until  the  edges  of  the 
precipitate  just  begin  to  fuse.  Cool  in  a  desiccator  and  weigh  the 
AgCl.  Calculate  to  HC1. 

CALCULATION.— AgCl  X  0.2544  =  HC1. 

Formic  Acid. — Weigh  8-10  grams  accurately  from  a  weighing 
bottle  into  a  500  cc.  graduated  flask  about  one-half  full  of  dis- 
tilled water.  Make  up  to  the  mark  and  mix  thoroughly.  Pipette 
50  cc.  of  this  solution  into  a  300  cc.  Erlenmeyer  flask.  Make  the 
solution  alkaline  with  Na2C03  solution.  Warm  and  add  a 
measured  excess  of  standard  0.1  N  KMn04.  It  is  very  necessary 
that  an  excess  of  the  permanganate  be  added.  This  oxidizes  the 
formic  acid  to  CO2  and  water  and  throws  down  a  heavy  precip- 
itate of  manganese  dioxide.  Then  acidify  with  10  cc.  of  dil. 


82  TECHNICAL  METHODS  OF  ANALYSIS 

H2S04.  Run  in  from  a  burette  a  measured  volume  of  0.1  N 
oxalic  acid  *  until  all  the  precipitate  has  dissolved  and  all  the 
permanganate  color  has  disappeared.  Finally  titrate  the  excess 
of  H2C2O4  with  the  0.1  N  KMnCU.  The  difference  between  the 
total  0.1  N  KMn04  used  and  the  amount  which  was  equivalent  to 
the  H2C2O4  gives  the  number  of  cc.  of  0.1  N  KMnO4  required  to 
oxidize  the  formic  acid. 

CALCULATION.— 1  cc.  0.1  N  KMnO4  =  0.002301  gram  formic 
acid. 

NOTE. — If  other  acids  are  known  to  be  absent,  the  amount  of  formic  acid 
can  be  determined  by  titrating  directly  with  0.1  N  NaOH  and  phenol- 
phthalein. 

1  cc.  0.1  N  NaOH  =0.004602  gram  formic  acid. 

REFERENCE.— Am.  Chem.  J.  17,  539  (1895). 

ACETIC  ANHYDRIDE 

General. — Acetic  anhydride  is  a  very  corrosive  substance  and 
its  vapors  are  extremely  irritating  to  the  eyes  and  lungs.  Care 
should  therefore  be  exercised  in  working  with  it,  and  any  spilled 
upon  the  hands  should  be  immediately  washed  off.  It  is  a  con- 
densation of  2  molecules  of  acetic  acid  with  elimination  of  water. 
The  reaction,  however,  is  reversible,  and  there  is  always  present 
some  acetic  acid,  due  to  action  of  water }  thus: 

(CH3CO)20+H20  ^  2CH3COOH. 

Determination  of  Anhydride  Content. — When  the  material  is 
pure  and  contains  only  acetic  anhydride  and  acetic  acid,  Method 
No.  1  (direct  titration),  described  below,  gives  satisfactory  results. 
In  case  of  impure  samples,  however,  Method  No.  2  (aniline  method) 
should  be  employed.  The  latter  method  is  the  one  employed  by 
the  U.  S.  Government  and  should  always  be  used  unless  otherwise 
expressly  directed. 

METHOD  No.  1.  DIRECT  TITRATION. — Weigh  accurately 
about  25  grams  from  a  weighing  bottle  into  a  2-liter  volumetric 
flask,  partly  filled  with  CO2-free  water;  let  stand  overnight, 

*  It  is  not  absolutely  necessary  to  have  the  oxalic  acid  of  a  definite  strength. 
In  case,  however,  it  is  not  0.1  N,  measure  off  a  volume  of  the  oxalic  acid  equal 
to  that  used  in  the  determination  and  titrate  it  against  the  0.1  N  KMnOi. 


GENERAL  ORGANIC  ANALYSES  83 

make  up  to  volume  with  CO2-free  water  and  titrate  50  cc. 
aliquots  with  0.1  N  NaOH  and  phenolphthalein.  Calculate  the 
titration  to  acetic  acid. 

1  cc.  0.1  N  NaOH  =  0.006004  gram  acetic  acid. 

Since  100%  of  acetic  anhydride  is  equivalent  to  117.651% 
of  acetic  acid,  then 

percentage  of  acetic  anhydride  =  — — —  X 100 

117 . ool — lOU 

=  5.665  (A -100), 
where  A  is  the  per  cent  of  acetic  acid  found  by  titration. 

NOTE. — As  any  error  in  the  acetic  acid  result  is  increased  nearly  sixfold 
in  the  final  results,  titration  should  be  carried  out  with  great  care  and  the  aver- 
age of  several  aliquots  should  be  taken.  Corrections  for  burette  calibrations 
must  be  made  and  also  corrections  for  temperature  effects  on  the  standard 
solution.  The  standard  NaOH  should  be  as  free  from  carbonate  as  possible. 

METHOD  No.  2.  ANILINE  METHOD. — Shake  the  sample 
thoroughly  and  rinse  a  burette  twice  with  portions  of  it.  Clean 
and  dry  two  50  cc.  weighing  bottles,  and  two  of  5  cc.  size.  (Do 
not  use  alcohol  for  drying  the  weighing  bottles  or  any  of  the 
apparatus  used  in  weighing  out  the  anhydride.) 

Into  each  of  the  5  cc.  weighing  bottles,  which  have  been  care- 
fully weighed,  run  2  cc.  of  anhydride  from  the  burette.  Imme- 
diately stopper  the  bottles  and  weigh  again  to  obtain  the  weight  of 
anhydride.  Then  drop  very  carefully  each  weighing  bottle  with  its 
contents  into  a  separate  300  cc.  Erlenmeyer  flask  containing  50  cc. 
of  N  NaOH  and  50  cc.  of  distilled  water.  Loosen  the  stopper  of  the 
weighing  bottle  slightly  before  dropping  it  into  the  flask,  so  that 
it  can  be  freed  from  the  weighing  bottle  and  the  contents  mixed 
with  the  NaOH  solution.  Let  the  mixture  stand  thirty  to  forty- 
five  minutes  at  room  temperature  with  occasional  shaking.  Then 
titrate  with  N  or  0.5  N  acid  and  phenolphthalein.  Add  2  or  3  cc. 
of  acid  in  excess  and  let  the  solution  stand  about  fifteen  minutes 
longer  with  occasional  shaking.  Finally  titrate  back  the  excess 
of  acid  with  0.1  N  NaOH  to  the  first  permanent  pink  color.  From 
this  titration  calculate  the  number  of  cc.  of  N  NaOH  represent- 
ing the  total  acetic  acid  from  100  grams  of  the  sample.  Call 
this  A. 


84  TECHNICAL  METHODS  OF  ANALYSIS 

Into  each  of  the  50  cc.  weighing  bottles  run  about  20  cc.  of 
perfectly  dry  and  recently  distilled  aniline.  (The  aniline  should 
be  distilled  over  solid  NaOH,  discarding  the  first  portion  of 
distillate.)  Then  add  2  cc.  of  anhydride  from  the  burette.  This 
operation  requires  considerable  care.  Do  not  add  the  anhydride 
too  rapidly,  and  distribute  it  through  the  aniline  as  thoroughly 
as  possible  by  keeping  the  aniline  swirling  slightly  in  the  weighing 
bottle  during  the  addition.  When  the  anhydride  has  been  added, 
stopper  the  bottle  and  set  aside  to  come  to  room  temperature; 
then  weigh  to  obtain  the  weight  of  anhydride  added. 

At  the  end  of  about  one  hour  from  the  time  of  addition  of 
anhydride  to  aniline,  transfer  the  mixture  to  a  500  cc.  volumetric 
flask  and  make  up  to  the  mark  with  a  solution  of  equal  parts  of 
neutral  alcohol  and  distilled  water.  Titrate  50  cc.  of  this  solu- 
tion with  0.1  N  NaOH.  From  this  titration  calculate  the  number 
of  cc.  of  N  NaOH  corresponding  to  the  residual  acetic  acid  from 
100  grams  of  the  sample.  Call  this  B. 

Subtract  B  from  A  to  obtain  the  number  of  cc.  of  N  NaOH 
corresponding  to  one-half  the  anhydride  in  100  grams  of  sample. 
This  value  multiplied  by  0.10207*  gives  grams  of  acetic  anhydride 
per  100  grams  of  sample,  i.e.,  the  percentage. 

Mineral  Acids. — Shake  up  a  portion  of  the  sample  with  cold 
water  and  test  the  solution  in  the  usual  way  for  HC1  with  AgNOs 
and  for  H2&O4  with  BaC^.  The  determination  may  be  made 
quantitative  by  starting  with  a  weighed  amount  of  the  anhydride 
sample. 

NOTE. — If  mineral  acids  are  found  present,  corrections  must  be  made  for 
the  amount  of  NaOH  they  will  neutralize  in  making  the  anhydride  titration. 

Boiling  Point. — The  boiling  point  of  pure  acetic  anhydride  is 
approximately  138°  C.  and  a  satisfactory  sample  should  all  distill 
between  130  and  140°  C. 

REFERENCE. — Worden:  "Technology  of  Cellulose  Esters,"  Vol.  VIII, 
pages  2910-2917. 

*  It  will  be  noted  that  the  factor  is  the  molecular  weight  of  acetic 
anhydride  divided  by  100.  The  method  may  be  applied  to  other  anhydrides, 
e.g.,  butyric  anhydride  (Mol.  Wt.  =  158.15),  in  which  case  the  factor  will 
be  0.01  of  the -molecular  weight  of  the  anhydride  in  question. 


GENERAL  ORGANIC  ANALYSES  85 

GLYCEROL 

General. — There  are  two  recognized  methods  for  the  deter- 
mination of  glycerol — (1)  the  acetin  method,  which  depends  upon 
the  conversion  of  glycerol  into  triacetin  with  sodium  acetate  and 
acetic  anhydride  and  a  quantitative  saponification  of  the  tri- 
acetin thus  formed;  (2)  the  bichromate  method,  which  is  based  on 
the  fact  that  K^C^O?  in  the  presence  of  H^SCX  completely 
oxidizes  glycerol  to  CO2  and  H^O. 

The  acetin  method  is  the  one  agreed  upon  at  a  conference  of 
delegates  from  the  British,  French,  German,  and  American  com- 
mittees on  glycerol  analysis  as  giving  results  nearer  to  the  truth 
than  the  bichromate  method  on  crude  glycerines  in  general. 
It  is  the  method  to  be  employed  whenever  possible,  but  for  the 
application  of  this  method  the  solution  must  not  contain  over  60% 
of  water.  In  general,  therefore,  use  the  acetin  method  for  crude 
or  refined  glycerines  and  the  bichromate  method  for  soap  lyes. 

ACETIN  METHOD 

Reagents  Required. — (A)  Best  Acetic  Anhydride. — This  should 
be  carefully  selected.  A  good  sample  must  not  require  more  than 
0.1  cc.  of  N  NaOH  for  saponification  of  the  impurities  when  a  blank 
is  run  on  7.5  cc.  Only  a  slight  color  should  develop  during  diges- 
tion of  the  blank.  (See  under  "  Blank  Test  "  below.) 

The  anhydride  may  be  tested  for  strength  by  the  aniline 
method  described  under  analysis  of  Acetic  Anhydride  (page  83). 

(B)  Pure  Fused  Sodium  Acetate. — Refuse  the  ordinary  salt  in  a 
platinum,  silica,  or  nickel  dish,  avoiding  charring,  powder  quickly 
and  keep  in  a  stoppered  bottle  or  desiccator.     It  is  very  important 
that  the  sodium  acetate  be  anhydrous. 

(C)  NaOH  (approximately  N  and  Free  from  Carbonate). — Dis- 
solve pure  NaOH  in  its  own  weight  of  water  (free  from  CO2). 
Let  settle  till  clear  or  filter  through  asbestos.     Dilute  the  clear 
solution  with  water  free  from  CO2  to  the  strength  required. 

(D)  N  NaOH  (Free  from  Carbonate). — Prepare   this  solution 
as  above  but  carefully  standardize  it.     Some  NaOH  solutions  show 
a  marked  diminution  in  strength  after  boiling;    such  solutions 
should  be  rejected. 


86  TECHNICAL  METHODS  OF  ANALYSIS 

(E)  N  Acid. — Standardize  this  against  the  N  NaOH. 

(F)  Phenolphthalein  Solution. — Dissolve  the  powder  in  alcohol 
sufficient  to  make  a  0.5%  solution  and  neutralize  with  N  NaOH 
to  a  very  slight  pink  color. 

Procedure. — In  a  narrow-mouthed  flask  (preferably  round- 
bottomed),  capacity  about  120  cc.,  which  has  been  thoroughly 
cleaned  and  dried,  weigh  accurately  and  as  rapidly  as  possible 
1.25-1.50  grams  of  the  glycerine.  A  Grethun  or  Lunge  pipette 
will  be  found  convenient.  Add  about  3  grams  of  anhydrous 
sodium  acetate  and  7.5  cc.  of  acetic  anhydride,  and  connect  the 
flask  with  an  upright  Liebig  condenser.  For  convenience  the  inner 
tube  of  this  condenser  should  not  be  over  50  cm.  long  and  9-10 
mm.  inside  diameter.  The  flask  is  connected  to  the  condenser  by 
either  a  ground  glass  joint  (preferably)  or  a  rubber  stopper.  If  a 
rubber  stopper  is  used  it  should  have  had  a  preliminary  treatment 
with  hot  acetic  anhydride  vapor. 

Heat  the  contents  and  keep  just  boiling  for  one  hour,  taking 
precautions  to  prevent  the  salts  from  drying  on  the  sides  of  the 
flask. 

Let  the  flask  cool  somewhat,  and  through  the  condenser  tube 
add  50  cc.  of  distilled  water,  free  from  CO2,  at  a  temperature  of 
about  80°  C.,  taking  care  that  the  flask  is  not  loosened  from  the 
condenser.  The  object  of  cooling  is  to  avoid  any  sudden  rush  of 
vapors  from  the  flask  on  adding  water,  and  to  avoid  breaking  the 
flask.  Time  is  saved  by  adding  the  water  before  the  contents  of 
the  flask  solidify,  but  the  contents  may  be  allowed  to  solidify  and 
the  test  proceeded  with  the  next  day  without  detriment,  bearing 
in  mind  that  the  anhydride  in  excess  is  much  more  effectively 
hydrolyzed  in  hot  than  in  cold  water.  The  contents  of  the  flask 
may  be  warmed  to,  but  must  not  exceed,  80°  C.  until  solution 
is  complete  (a  few  dark  flocks  may  remain  in  suspension,  repre- 
senting organic  impurities  in  the  crude  glycerine).  By  giving  the 
flask  a  rotary  motion,  solution  is  more  quickly  effected. 

Cool  the  flask  and  contents  without  removing  the  condenser. 
When  quite  cold,  wash  down  the  inside  of  the  condenser  tube, 
detach  the  flask,  wash  off  the  stopper  or  ground  glass  connection 
into  the  flask,  and  filter  the  contents  through  an  acid-washed  filter 
into  a  Pyrex  glass  flask  of  about  1  liter  capacity.  Wash  thoroughly 
with  cold  distilled  water  free  from  CC>2.  Add  2  cc.  of  phenol- 


GENERAL  ORGANIC  ANALYSES  87 

phthalein  solution  (F),  then  run  in  NaOH  solution  (C)  or  (D) 
until  a  faint  pinkish  yellow  color  appears  throughout  the  solution. 
This  neutralization  must  be  done  most  carefully;  the  alkali 
should  be  run  down  the  sides  of  the  flask,  the  contents  of  which  are 
kept  rapidly  swirling  with  occasional  agitation  or  change  of  motion 
until  the  solution  is  nearly  neutralized,  as  indicated  by  the  slower 
disappearance  of  the  color  developed  locally  by  the  alkali  running 
into  the  mixture.  When  this  point  is  reached  the  sides  of  the  flask 
are  washed  down  with  C02-free  water  and  the  alkali  subsequently 
added,  drop  by  drop,  mixing  after  each  drop  until  the  desired  tint 
is  obtained. 

Now  run  in  from  a  burette  50  cc.  or  a  calculated  excess  of  N 
NaOH  (D)  and  note  carefully  the  exact  amount.  Boil  gently 
for  fifteen  minutes,  the  flask  being  fitted  with  a  glass  tube  acting 
as  a  partial  condenser.  Cool  as  quickly  as  possible  and  titrate 
the  excess  of  NaOH  with  N  acid  (E)  until  the  pinkish  yellow  or 
chosen  end-point  color  just  remains.*  A  further  addition  of  the 
indicator  at  this  point  will  cause  an  increase  of  the  pink  color; 
this  must  be  neglected,  and  the  first  end  point  taken. 

From  the  N  NaOH  consumed  calculate  the  percentage  of 
glycerol  (including  acetylizable  impurities)  after  making  the  cor- 
rection for  the  blank  test  described  below. 

1  cc.  N  NaOH  =  0.03069  gram  glycerol. 

The  coefficient  of  expansion  for  normal  solutions  is  0.00033 
per  cc.  for  each  degree  Centigrade.  A  correction  should  be  made 
on  this  account  if  necessary. 

Blank  Test. — As  the  acetic  anhydride  and  sodium  acetate 
may  contain  impurities  which  affect  the  result,  it  is  necessary  to 
make  a  blank  test,  using  the  same  quantities  of  acetic  anhydride, 
sodium  acetate  and  water  as  in  the  analysis.  It  is  not  necessary 
to  filter  the  solution  of  the  melt  in  this  case,  but  sufficient  time 
must  be  allowed  for  the  hydrolysis  of  the  anhydride  before  pro- 
ceeding with  the  neutralization.  After  neutralization  it  is  not 
necessary  to  add  more  than  10  cc.  of  the  N  alkali  (D),  as  this 
represents  the  excess  usually  present  after  the  saponification  of 

*A  precipitate  at  this  point  is  an  indication  of  the  presence  of  iron  or 
alumina,  and  high  results  will  be  obtained  unless  a  correction  is  made  as 
described  below. 


88  TECHNICAL  METHODS  OF  ANALYSIS 

the  average  soap  lye  crude.  In  determining  the  acid  equivalent 
to  the  N  NaOH,  however,  the  entire  amount  taken  in  the  analysis, 
50  cc.,  should  be  titrated  after  dilution  with  300  cc.  of  water  free 
from  CC>2  and  without  boiling. 

Determination  of  the  Glycerol  Value  of  the  Acetylizable  Im- 
purities.— Certain  crude  glycerines  may  contain  a  considerable 
amount  of  acetylizable  impurities  other  than  glycerol.  To  deter- 
mine the  amount  of  these  impurities,  dissolve  the  total  residue 
at  160°  C.  (see  below)  in  1  or  2  cc.  of  water,  wash  into  the  acetylizing 
flask  and  evaporate  to  dryness.  Then  add  anhydrous  sodium 
acetate  and  acetic  anhydride  in  the  usual  amounts  and  proceed 
as  described  iri  the  regular  analysis. 

True  Glycerol  Content. — After  correcting  for  the  blank  cal- 
culate the  result  obtained  in  the  preceding  paragraph  to  glycerol 
and  subtract  the  amount  from  the  total  amount  of  glycerol 
obtained  in  the  analysis. 

Total  Residue  at  160°  C.— If  the  glycerine  is  acid,  make  it 
slightly  alkaline  with  Na2COs  to  prevent  the  loss  of  organic  acids. 
To  avoid  the  formation  of  polyglycerols  this  alkalinity  must  not 
exceed  0.2%  Na2O.  If,  therefore,  the  glycerine  is  too  strongly 
alkaline,  sufficient  N  HC1  must  be  added  to  bring  the  alkalinity 
down  to  0.2%. 

Place  10  grams  of  the  sample  in  a  100  cc.  flask,  dilute  with 
water  and  add  the  calculated  quantity  of  N  HC1  or  Na2CO3  to 
give  the  required  degree  of  alkalinity.  Dilute  to  100  cc.,  mix 
thoroughly  and  pipette  10  cc.  into  a  weighed  Petri  or  similar 
dish,  2.5  inches  in  diameter  and  0.5  inch  deep,  with  a  flat  bottom. 
In  the  case  of  crude  glycerines  abnormally  high  in  organic  residue, 
a  smaller  amount  should  be  taken  so  that  the  amount  of  the 
organic  residue  does  not  materially  exceed  30-40  milligrams. 

Place  the  dish  on  a  water  bath  until  most  of  the  water  is  evap- 
orated, then  place  in  an  oven  and  evaporate  the  glycerine,  or 
most  of  it  at  least,  at  a  temperature  of  130-140°  C.  When  only 
a  slight  vapor  is  seen  to  come  off,  take  off  the  dish  and  let  it 
cool.  Add  0.5-1  cc.  of  water  and  bring  the  residue  wholly  or 
nearly  into  solution  with  a  rotary  motion.  Place  the  dish  on  the 
water  bath  or  on  top  of  the  oven  until  the  excess  water  has  evap- 
orated and  the  residue  is  in  such  a  condition  that  it  will  not  spurt 
if  the  oven  is  raised  to  160°  C.  In  the  meantime  set  the  oven  at 


GENERAL  ORGANIC  ANALYSES  89 

exactly  160°  C.  From  this  point  the  time  of  heating  must  be 
strictly  observed.  Place  the  dish  in  the  oven  and  maintain  at 
exactly  160°  C.  for  one  hour.  Remove  the  dish,  cool,  treat  the 
residue  with  water,  and  evaporate  the  water  as  before.  Then  place 
the  dish  again  in  the  oven  and  heat  a  second  time  for  exactly  one 
hour.  Place  the  dish  in  a  desiccator  and  let  cool  over  H2SO4. 
Weigh  the  cooled  dish.  Again  moisten  with  water  and  heat  at 
160°  C.  for  one  hour.  Repeat  the  operation  until  a  constant  loss 
of  1-1.5  mg.  per  hour  is  obtained. 

In  the  case  of  acid  glycerine  correct  for  the  N  Na2CC>3  added 
by  subtracting  0.03  gram  for  each  cc.  added.  In  the  case  of 
alkaline  glycerine  correct  for  the  amount  of  N  HC1  added  by 
calculating  the  increase  in  weight  due  to  the  conversion  of  the 
NaOH  and  Na2C03  to  NaCl.  From  the  corrected  weight  calcu- 
late the  percentage  of  total  residue  at  160°  C.  This  residue  is 
taken  for  the  determination  of  the  non-volatile  acetylizable  impuri- 
ties. (See  above.) 

BICHROMATE  METHOD 

Reagents  Required. — (A)  Pure  K2Cr207j  powdered  and  dried 
at  110-120°  C.  in  air  free  from  dust  or  organic  vapors.  This  is 
taken  as  the  standard. 

(B)  Dilute  Bichromate  Solution. — Dissolve  7.4564  grams  of  the 
above  bichromate  in  distilled  water  and  make  up  the  solution 
to  1  liter  at  15.5°  C. 

(C)  Ferrous  Ammonium  Sulfate. — It  is  never  safe  to  assume  this 
salt  to  be  constant  in  composition,  and  the  solution  must  be 
standardized  against  the  bichromate  as  follows: 

Dissolve  3.7282  grams  of  bichromate  (A)  in  50  cc.  of  water. 
Add  50  cc.  of  50%  H2S04  (by  volume),  and  to  the  cold  undiluted 
solution  add  from  a  weighing  bottle  a  moderate  excess  of  the 
ferrous  ammonium  sulfate,  and  titrate  back  with  the  dilute 
bichromate  (B).  Calculate  the  value  of  the  ferrous  salt  in  terms 
of  bichromate. 

(D)  Silver  Carbonate. — Prepare  this  as  required  for  each  test. 
Make  up  a  0.5%  Ag2SO4    solution   and  precipitate  the  Ag2CO3 
from  140  cc.  of  this  solution  with  about  4.9  cc.  of  N  Na2CO3  solution 
(a  little  less  than  the  calculated  quantity  of  N  Na2CO3  should 


90  TECHNICAL  METHODS  OF  ANALYSIS 

be  used  as  an  excess  prevents  rapid  settling).     Let  settle,  pour 
off  the  liquid  and  wash  once  by  decantation. 

(E)  Subacetate  of  Lead. — Boil  a  10%  solution  of  pure  lead  ace- 
tate with  an  excess  of  litharge  (PbO)  for  one  hour,  keeping  the 
volume  constant,  and  filter  while  hot.     Disregard  any  precipitate 
which  subsequently  forms.     Preserve  out  of  contact  with  CCb. 

(F)  Potassium   Ferricyanide. — Use   a   freshly  prepared,  very 
dilute  (about  0.1%)  solution  of  this  salt. 

Procedure. — Weigh  out  20  grams  of  the  glycerine,  make  up 
with  water  to  250  cc.  in  a  volumetric  flask  and  pipette  out  25  cc. 
into  a  100  cc.  graduated  flask.  To  this  add  the  Ag2CO3,  let  stand 
with  occasional  agitation  for  about  ten  minutes,  and  add  a  slight 
excess  (about  5  cc.  in  most  cases)  of  basic  lead  acetate  (E).  Let 
stand  a  few  minutes,  dilute  with  distilled  water  to  100  cc.  and  then 
add  0.15  cc.  to  compensate  for  the  volume  of  the  precipitate. 
Mix  thoroughly,  filter  through  an  air-dry  filter  into  a  test  tube, 
rejecting  the  first  10  cc.  and  return  the  filtrate,  if  not  clear  and 
bright.  Test  a  portion  of  the  filtrate  with  a  little  basic  lead 
acetate,  which  should  produce  no  further  precipitate.  In  the 
great  majority  of  cases  5  cc.  are  ample,  but  occasionally  a  crude 
will  be  found  requiring  more,  and  in  this  case  another  aliquot  of 
25  cc.  of  the  dilute  glycerine  should  be  taken  and  purified  with 
6  cc.  of  basic  lead  acetate.  Care  must  be  taken  to  avoid  a  marked 
excess  of  basic  acetate. 

When  the  filtrate  is  coming  through  perfectly  clear,  collect 
sufficient  in  an  Erlenmeyer  flask  so  that  25  cc.  may  be  pipetted 
into  a  flask  or  beaker  which  has  been  previously  cleaned  with 
K2Cr207  and  H2SO4.  To  this  add  12  drops  of  H2SO4  (1  : 4)  to 
precipitate  the  small  excess  of  lead  as  PbSO4.  Then  add  3.7282 
grams  of  the  powdered  K2Cr207.  Rinse  down  the  bichromate 
with  25  cc.  of  water  and  let  stand  with  occasional  shaking  until 
all  the  bichromate  is  dissolved.  (No  reduction  will  take  place  in 
the  cold.) 

Add  50  cc.  of  50%  (by  volume)  H2S04,  immerse  the  vessel  in 
boiling  water  for  two  hours  and  keep  protected  from  dust  and 
organic  vapors,  such  as  alcohol,  until  the  titration  is  completed. 
Add  from  a  weighing  bottle  a  slight  excess  of  the  ferrous  ammo- 
nium sulfate,  making  spot  tests  on  a  porcelain  plate  with  ferri- 
cyanide  indicator  until  an  excess  is  shown.  Then  titrate  back 


GENERAL  ORGANIC  ANALYSES  91 

with  the  dilute  bichromate  solution.     Calculate  the  percentage 
of  glycerol  from  the  amount  of  bichromate  reduced. 

CALCULATION.  —  1  gram  K2Cr2O7  =  0.13411  gram  glycerol. 


NOTES.  —  (1)  The  percentage  of  glycerol  obtained  above  includes  any 
oxidizable  impurities  present  after  the  purification.  A  correction  for  the  non- 
volatile impurities  may  be  made  by  running  a  bichromate  test  on  the  residue 
at  160°  C. 

(2)  It  is  important  that  the  concentration  of  acid  in  the  oxidation  mixture 
and  the  time  of  oxidation  should  be  strictly  adhered  to. 

(3)  Before  the  bichromate  is  added  to  the  glycerine  solution  it  is  essential 
that  the  slight  excess  of  lead  be  precipitated  with  H2SO4,  as  stipulated. 

(4)  For  crudes  practically  free  from  chlorides  the  quantity  of  Ag2COa 
may  be  reduced  to  one-fifth  and  the  basic  lead  acetate  to  0.5  cc. 

(5)  It  is  sometimes  advisable  to  add  a  little  K2SO4  to  insure  a  clear  filtrate. 

(6)  Neither  the  acetin  nor  bichromate  method  is  correct  in  theory  or  in 
practice  on  crudes  containing  trimethyleneglycol  or  polyglycerols  but  the 
acetin  method  gives  nearer  the  truth. 

REFERENCE.—  J.  Ind.  Eng.  Chem.  3,  679  (1911).  Approved  Report  of 
the  Sub-committee  on  Glycerine  Analysis. 

DEXTRIN  OR  BRITISH  GUM 

General.  —  Dextrin  corresponds  to  the  formula  (CeHioOs^  and 
is  generally  considered  an  intermediate  product  between  starch 
and  dextrose.  The  commercial  product  is  made  by  heating  dry 
starch  to  200-250°  C.  or  by  moistening  the  starch  with  acid,  drying 
at  50°  C.  and  then  heating  to  140-170°  C.  The  product  is  an 
indefinite  mixture  of  several  dextrins  with  unchanged  starch  and 
may  also  contain  more  or  less  dextrose.  The  dextrins  are  soluble 
in  cold  water  and  form  a  thick  viscous  syrup  which  has  strong 
adhesive  properties  and  is  much  used  as  a  substitute  for  gum 
arabic  in  the  preparation  of  mucilage  and  for  thickening  color  in 
calico  printing,  etc. 

Moisture.  —  Dry  5  grams  to  constant  weight  at  100°  C.  in  a 
weighed  platinum  dish. 

Ash.  —  Ignite  carefully  the  residue  from  the  moisture  deter- 
mination to  a  white  or  grayish  white  ash.  Cool  in  a  desiccator 
and  weigh. 

Insoluble  in  Cold  Water  (Starch)  .—Stir  into  about  250  cc.  of 
water  25  grams  of  the  sample.  Wash  into  a  500  cc.  graduated 
flask,  Shake  occasionally  for  several  hours,  dilute  to  volume  and 


92  TECHNICAL  METHODS  OF  ANALYSIS 

let  stand  overnight.  Pipette  out  50  cc.  of  the  clear  supernatant 
liquor,  evaporate  in  a  weighed  dish  on  the  water  bath  and  dry  to 
constant  weight  at  100°  C.  This  gives  the  weight  of  the  soluble 
solids  in  2.5  grams.  Divide  by  2.5  and  multiply  by  100  to  obtain 
the  percentage  of  soluble  solids.  Add  to  this  the  percentage  of 
moisture  and  subtract  the  sum  from  100%.  The  difference  is 
insoluble  matter  (unconverted  starch). 

Dextrose.  (Munson  and  Walker  Method.) — Mix  10  grams  of 
the  sample  with  water,  stir  thoroughly  and  wash  into  a  250  cc. 
graduated  flask.  Add  5  cc.  of  lead  subacetate  solution,  dilute  to 
volume,  mix  thoroughly,  let  settle  and  filter  through  a  dry  filter. 
Do  not  wash.  Add  a  few  crystals  of  anhydrous  K2C2O4  to  remove 
the  lead  and  again  filter  through  a  dry  filter.  Pipette  out  50  cc. 
of  this  solution  and  determine  reducing  sugars  according  to  the 
Munson  and  Walker  method  described  on  page  403.  Calculate 
to  dextrose,  using  the  third  column  of  figures  in  the  Munson  and 
Walker  tables. 

Dextrin. — Pipette  100  cc.  of  the  solution  of  the  material  pre- 
pared for  the  dextrose  determination  (after  the  lead  has  been 
removed  and  the  solution  filtered),  into  a  250  cc.  flask,  add  20  cc. 
of  HC1  (1:1)  and  100  cc.  of  water.  Heat  in  a  boiling  water  bath 
for  2.5  hours.  Cool  and  nearly  neutralize  to  litmus  paper  with 
NaOH.  Dilute  to  500  cc.  in  a  graduated  flask,  pipette  out  50  cc. 
(equivalent  to  0.4  gram  of  the  original)  and  determine  the  reducing 
sugars  by  the  Munson  and  Walker  method  as  described  above  under 
"  Dextrose."  Calculate  the  total  reducing  sugars  as  dextrose. 
Subtract  from  this  figure  the  percentage  of  dextrose,  previously 
determined,  and  multiply  the  difference  by  0.9  to  obtain  the  per 
cent  of  dextrin. 

NOTE. — By  this  method  the  amount  of  soluble  starch,  if  any,  is  included 
with  the  dextrin,  but  as  their  properties  are,  for  textile  purposes,  quite  sim- 
ilar, the  additional  work  involved  in  the  separation  is  not  worth  while. 

Viscosity. — Determine  the  viscosity  by  means  of  a  Dudley 
pipette  at  25°  C.  The  pipette  should  be  standardized  with  a  sugar 
solution  made  by  dissolving  120  grams  of  pure  cane  sugar  in  100  cc. 
of  distilled  water  at  25°  C.  This  solution  should  give  a  viscosity 
of  about  100  seconds.  In  determining  the  viscosity,  the  pipette 
should  be  surrounded  by  a  jacket  containing  water  at  the  same 


GENERAL  ORGANIC  ANALYSES.  93 

temperature.  Fill  the  pipette  slightly  above  the  mark  with  the 
solution,  then  set  it  exactly  on  the  upper  mark.  Release  the 
solution  with  one  hand  and  start  the  stop  watch  with  the  other. 
Determine  the  number  of  seconds  required  by  the  solution  to  run 
from  the  top  mark  to  the  bottom  mark.  Several  determinations 
should  be  made  and  the  average  reported.  After  standardizing 
the  pipette  with  sugar  solution  determine  the  viscosity  of  a  solution 
of  the  sample  in  the  same  way.  Mix  40  grams  of  the  sample 
with  about  150  cc.  of  distilled  water,  heat  to  boiling  for  exactly 
one  minute,  stirring  thoroughly;  transfer  to  a  200  cc.  flask,  cool 
and  make  up  to  volume  at  25°  C.  Use  this  solution  for  the  vis- 
cosity determination. 

NOTE. — The  viscosity  of  the  solution  depends  largely  on  the  time  of  heating. 
The  material  should  be  stirred  up  with  a  little  warm  water  and  then  trans- 
ferred rapidly  to  a  beaker  containing  the  rest  of  the  water  which  should  be 
near  the  boiling  point.  It  should  be  rapidly  heated  to  boiling  and  boiled 
for  exactly  one  minute. 

ALBUMIN 

General. — Commercial  albumin  is  chiefly  from  two  sources, 
eggs  and  blood-serum.  The  latter  is  cheaper  than  egg  albumin 
and  has  a  better  thickening  power.  It  is  largely  used  for  fixing  dyes 
and  pigments  in  calico  printing  in  all  but  the  finest  colors.  The 
blood-serum  albumin  varies  from  a  dirty  yellow  color  to  the  black 
color  of  "  dried  blood."  Egg  albumin  is  generally  transparent 
and  of  a  light  yellow  color.  It  should  be  free  from  blisters  which 
indicate  partial  coagulation.  On  treatment  with  cold  water, 
commercial  albumin  of  good  quality  should  dissolve  almost  com- 
pletely. In  making  the  test,  the  albumin  should  always  be  added 
to  the  water  and  not  vice  versa.  (If  it  is  desired  to  keep  the  solu- 
tion, add  about  1%  of  arsenious  oxide.) 

Qualitative  Tests.— Commercial  albumin  is  frequently  adul- 
terated with  dextrin,  gums,  sugar,  flour,  etc.  For  qualitative 
examination  grind  to  a  powder  and  add  5  grams  (accurately 
weighed)  slowly  to  about  50  cc.  of  water  until  the  soluble  matter  is 
dissolved.  Pure  and  high-grade  samples  should  leave  no  residue. 
Add  a  few  drops  of  acetic  acid  and  filter  through  silk  or  fine  muslin 
into  a  500  cc.  volumetric  flask.  The  insoluble  residue  may  con- 


94  TECHNICAL  METHODS  OF  ANALYSIS 

sist  of  coagulated  albumin,  casein,  starch,  or  membranous  matter. 
Treat  it  with  very  dilute  NaOH  solution  and  then  exactly  neu- 
tralize the  nitrate  with  acetic  acid.  If  casein  is  present  it  will  be 
dissolved  by  the  NaOH  and  reprecipitated  on  neutraliza- 
tion.. 

Make  the  original  filtrate  up  to  500  cc.  Pour  about  100  cc. 
into  a  beaker  and  heat  to  boiling.  This  should  coagulate  the 
albumin.  Filter  and  treat  the  filtrate  with  a  little  acetic  acid  and 
potassium  ferrocyanide  to  make  sure  that  no  proteins  remain  in 
the  solution.  If  there  is  a  precipitate,  filter  it  out.  (A  precip- 
itate generally  indicates  casein,  although  it  must  be  remembered 
that  any  zinc  would  be  thrown  out  as  white  ferrocyanide.)  Cool 
the  filtrate  and  add  a  little  concentrated  tannic  acid  solution. 
This  will  precipitate  any  gelatin  or  glue.  Filter,  and  concen- 
trate the  filtrate  to  a  small  bulk.  Cool  and  treat  with  a  con- 
siderable excess  of  alcohol.  Any  precipitate  indicates  the  presence 
of  gums  or  dextrin.  Filter,  boil  off  all  the  alcohol,  heat  with  dilute 
HC1  and  test  the  solution  in  the  usual  way  with  Fehling's  solution 
after  neutralizing  excess  of  HC1.  Any  reduction  indicates  the 
presence  of  sugar  but  does  not  necessarily  prove  its  presence. 
Sugar  may  also  be  extracted  by  treating  the  original  solid  sample 
with  alcohol. 

Soluble  Coagulable  Albumin. — Pipette  100  cc.  of  the  original 
water  solution  (equivalent  to  1  gram)  into  a  beaker.  Add  about 
1  gram  of  sodium  acetate  and  heat  to  boiling.  Filter*  the  floc- 
culent  precipitate  on  a  tared  filter  using  a  platinum  cone  and  suc- 
tion. Wash  with  hot  water,  dry  at  100°  C.  and  weigh. 

Moisture. — Dry  2  grams  of  the  material  in  a  weighed  porce- 
lain dish  to  constant  weight  at  100°  C.  Report  the  loss  as 
moisture. 

Ash. — Instead  of  determining  the  actual  residue  on  ignition  ia 
the  usual  way,  it  is  better  on  account  of  the  fusible  nature  of  the 
ash  to  proceed  as  follows: 

Treat  the  residue  from  the  moisture  determination  with  a 
few  drops  of  cone.  HNO3  and  2  or  3  drops  of  H2S04.  On  heating 
gently,  the  albumin  dissolves  to  a  clear  yellow  liquid  which  may 
be  evaporated  to  dryness  without  trouble.  Ignite  the  dry  residue 
and  weigh.  Report  the  result  as  "  sulfate  ash."  Allen  gives  the 
following  results  obtained  on  various  samples: 


GENERAL  ORGANIC  ANALYSES 


95 


Designation. 

Sulfate  Ash, 
Per  Cent. 

Itjiiti  albumin                                  ... 

No.  1 

7  4 

No   2 

7  0 

Blood-serum,  albumin.              

Refined 

9.1 

Blood-serum  albumin  

Prime 

8.5 

Blood-serum  albumin               

No.  1 

9.2 

Blood-serum  albumin 

No  2 

8  9 

Blood-serum  albumin  

No.  3 

9.7 

Blood-serum  albumin                   

Black 

6.2 

The  addition  of  sugar  or  dextrin  to  the  albumin  would  lower 
the  amount  of  ash.  If  it  is  abnormally  high  it  may  also  be  exam- 
ined for  zinc  or  other  inorganic  materials. 

REFERENCE. — Allen:  "Commercial  Organic  Analysis"  (2d  ed.,  1898), 
Vol.  IV,  page  44. 


TANNIC  ACID 

General. — Many  processes  have  been  devised  for  estimating 
tannic  acid  in  the  substances  known  as  "  Tannins."  Most  of 
these  methods,  however,  have  had  in  view  the  valuation  of  tannins 
for  tanning  leather,  but  it  does  not  necessarily  follow  that  they  are 
equally  serviceable  for  valuing  tannins  when  used  in  dyeing. 

Proctor's  modification  of  LoewenthaFs  method  has  been  very 
generally  adopted  both  for  tanning  and  dyeing  purposes.  Never- 
theless, if  the  tannin  is  to  be  used  in  the  leather  industries,  the 
Loewenthal  method  of  analysis  should  not  be  used.  In  such 
cases  use  the  Official  Method  of  the  American  Leather  Chemists' 
Association. 

The  determinations  most  generally  required  on  tannins  or 
tannic  acid  for  dyeing  purposes  are  as  follows: 

Moisture.— Weigh  1  gram  if  the  material  is  solid,  5  grams  if 
liquid,  in  a  platinum  crucible  or  dish  and  dry  at  100°  C.  to  con- 
stant weight.  Report  loss  in  weight  as  moisture. 

Ash. — Ignite  the  above,  carefully  at  first,  and  finally  to  the 
full  heat  of  the  Bunsen  burner;  cool  in  a  desiccator  and  weigh. 

Total  Astringency  (Loewenthal-Proctor  Method.). — Dissolve 
1  gram  in  water  and  dilute  to  1  liter.  Pipette  10  cc.  of  this  solu- 


96  TECHNICAL  METHODS  OF  ANALYSIS 

tion  into  a  large  porcelain  dish  containing  750  cc.  of  water.  Add 
25  cc.  of  indigo  carmine  solution  and  titrate  with  standard  KMnO4 
exactly  as  under  Sumac  analysis  (page  479). 

Astringent  Non-tannins. — To  50  cc.  of  the  above  solution  in  a 
strong  8-ounce  bottle,  add  25  cc.  of  2%  gelatin  solution,  25  cc.  of 
saturated  NaCl  acid  solution  and  10  grams  of  china  clay.  Shake 
thoroughly  for  about  five  minutes  and  filter  through  a  dry  filter. 
This  removes  the  tannins.  Test  a  portion  of  the  filtrate  with  more 
of  the  gelatin  solution  to  see  if  precipitation  is  complete.  (If 
not  complete,  make  up  a  gelatin  solution  stronger  than  2%  and 
repeat  the  process,  using  25  cc.  of  the  latter  solution.)  Titrate 
20  cc.  of  this  filtrate,  equivalent  to  10  cc.  of  the  original  solution, 
and  calculate  the  percentage  of  astringent  non-tannins. 

Tannic  Acids  or  Tannins. — The  difference  between  the  total 
astringency,  calculated  as  tannin,  and  the  astringent  non-tannins 
gives  the  percentage  of  tannins. 

NOTES. — (1)  The  solutions  referred  to  above  are  made  as  follows: 
(a)  Indigo  Carmine  Solution. — Dissolve  5  grams  of  pure  indigo  carmine  in 
water,  add  50  grams  of  cone.  H2SO4  and  dilute  to  1  liter.     If  indigo  carmine  is 
not  available,  sulfonate  1  gram  of  pure  indigo  with  60  cc.  of  cone.  H2SO4  for  six 
hours  at  70-80°  C.  and  dilute  with  H2O  to  1  liter. 

(6)  KMn04  Solution  (approx.  0.01  N).— This  should  be  accurately  stand- 
ardized against  oxalic  acid  or  sodium  oxalate. 

(c)  Gelatin  Solution. — Soak  20  grams  of  Nelson's  gelatin  in  water  for  two 
or  three  hours.     Then  dissolve  on  the  steam  bath  with  the  addition  of  more 
water  and  dilute  to  1  liter. 

(d)  Saturated  NaCl  Add  Solution. — Make  up  a  5  per  cent  solution  of  H2SO4 
and  saturate  with  ordinary  salt. 

(2)  In  calculating  the  tannin  titrations  use  the  factor  1  cc.  0.1  N  KMnO4  = 
0.004157  gram  tannin. 

(3)  It  is  often  customary  in  analyzing  mixed  tannins  or  extracts  containing 
tannin  to  calculate  the  tannin  in  terms  of  oxalic  acid. 

1  cc.  0.1  N  KMnO4  =  0.006303  gram  H2C2O4-2H2O. 

(4)  The  above  method  is  especially  intended  for  pure  tannic  acid  and 
tannins  for  use  in  dyeing. 

REFERENCE. — Knecht-Rawson-Loewenthal :  "  Manual  of  Dyeing,"  Vol.  II, 
2d  Edition,  page  802. 


GENERAL  ORGANIC  ANALYSES  97 

INDIGO 
POWDER   OR   PASTE 

General. — The  methods  employed  for  testing  indigo  may  be 
broadly  classified  into  three  groups: 

(1)  Conversion  into  sulfonic  acid. 

(a)  Indigotin  estimated  by  oxidation. 
(6)  Indigotin  estimated  by  reduction. 

(2)  Indigotin  reduced  in  an  alkaline  solution,    the  indigo  tin 
re-oxidized,  separated,  purified,  and  weighed,  or  dissolved  in  acid 
and  titrated  as  in  (1). 

(3)  Extraction  by  volatile  solvents. 

There  are  two  kinds  of  indigo  met  with,  natural  and  synthetic. 
At  the  present  time  the  synthetic  has  practically  replaced  the 
natural.  (The  European  War,  however,  has  stimulated  again  the 
production  of  natural  indigo.) 

The  natural  indigo  usually  comes  in  the  form  of  lumps  and 
contains  besides  indigo  blue,  or  indigotin,  other  substances  both 
of  organic  and  inorganic  nature  which  owe  their  presence  to  the 
process  of  manufacture.  Their  amount  varies  according  to  the 
quantity  of  indigo  blue  that  is  contained  in  the  sample  and  varies 
widely  in  indigoes  of  different  origin. 

The  mineral  impurities  consist  of  sand,  silicates,  and  CaCOs. 
The  organic  impurities  consist  of  (1)  indigo  gluten  or  gum,  (2) 
indigo  brown,  and  (3)  indigo  red  or  indirubin. 

Synthetic  indigo  is  practically  pure  indigotin  and  is  usually 
put  out  in  the  form  of  a  paste  containing  about  20%  indigotin  and 
80%  water. 

Moisture. — If  the  sample  is  in  the  form  of  lumps,  grind  to  a 
fine  powder  and  dry  1  gram  at  100-105°  C.  to  constant  weight. 
If  the  sample  is  in  the  form  of  a  paste,  mix  thoroughly  and  weigh 
out  as  rapidly  as  possible  10-15  grams  and  dry  to  constant  weight 
at  100-105°  C.  Report  loss  in  weight  as  moisture. 

Indigotin.  (By  reduction  with  hydrosulfite.) — This  method 
gives  the  most  exact  figures  for  the  indigotin  content  and  is  not 
influenced  by  the  impurities  contained  in  the  indigo.  It  also  is 
the  quickest  method  and  the  danger  of  errors  is  reduced  to  a 


98  TECHNICAL  METHODS  OF  ANALYSIS 

minimum  owing  to  the  change  in  color  being  very  easy  to  recog- 
nize. 

SULFONATION. — Weigh  accurately  1  gram  of  the  very  finely 
powdered  dry  indigo  and  heat  for  five  hours  with  6  cc.  of  cone. 
H2S04  at  105-120°  F.  with  frequent  stirring,  then  pour  into  water 
and  make  up  to  1  liter.  In  the  case  of  natural  indigo  there  is 
usually  an  insoluble  residue  which,  however,  contains  no  indigotin. 
The  temperature  should  not  be  allowed  to  exceed  120°  F.  as  other- 
wise much  darker  solutions  are  obtained,  which  render  the  titration 
more  difficult. 

PKEPARATION  OF  SOLUTIONS. — Any  freshly  prepared  solution 
of  sodium  hydrosulfite  may  be  used  as  a  titrating  solution,  pro- 
vided that  it  does  not  contain  more  than  1%  alkali.  It  is  advisable 
to  use  a  hydrosulfite  solution  of  such  strength  that  25-30  cc.  will 
decolorize  0.1  gram  of  indigo  or  100  cc.  of  an  0.1%  solution  of 
indigo.  To  prepare  the  hydrosulfite  solution  mix  400  cc.  of  sodium 
bisulfite  liquor  of  sp.  gr.  1.36-1.38  (72-76°  Tw.)  with  950  cc.  of 
H2O,  and  then  add  35  grams  of  zinc  powder  which  has  been  pre- 
viously worked  to  a  paste  with  50  cc.  of  H^O.  The  zinc  paste 
should  all  be  added  within  fifteen  minutes  in  small  portions,  stirring 
or  shaking  gently.  After  the  mixture  has  stood  for  one  hour,  draw 
off  the  clear  liquid  into  lime  water  prepared  by  slaking  45  grams 
of  good  quicklime  with  200  cc.  hot  water.  Stir  the  mixture  for 
some  time  and  then  let  it  stand  quietly  for  about  twelve  hours. 
Then  draw  off  the  clear  hydrosulfite  solution  and  add  for  every 
liter  5  cc.  of  NaOH  solution  of  sp.  gr.  1.38  (76°  Tw.).  The  solution 
should  show  a  distinctly  alkaline  reaction.  If  it  does  not,  add  a 
little  more  NaOH  solution. 

Standardization  of  Hydrosulfite  Solution. — Weigh  out  accu- 
rately 1  gram  of  pure  standard  indigo  powder  of  known  indigotin 
content  and  sulfonate  as  above  described  under  "  sulfonation." 
Make  this  up  to  1  liter  with  distilled  water.  Pipette  100  cc.  of 
this  solution  into  a  flask  and  run  in  from  a  burette  the  hydro- 
sulfite solution  until  all  the  blue  color  has  disappeared.  A  stream 
of  CO2  or  illuminating  gas  must  be  run  into  the  titrating  flask  to 
expel  all  air  and  have  a  reducing  atmosphere  before  the  titration  is 
begun.  The  tip  of  the  burette  should  be  drawn  out  to  a  point 
about  8-10  cm.  long.  Have  this  tip  below  the  surface  of  the 
liquid  until  the  blue  color  has  nearly  disappeared.  Then  raise 


GENERAL  ORGANIC  ANALYSES 


99 


the  tip  and  run  in,  drop  by  drop,  the  hydrosulfite  solution  until 
all  the  color  has  disappeared.  This  must  be  done  as  rapidly  as 
possible  to  prevent  oxidation. 

From  the  titration  calculate  the  strength  of  the  hydrosulfite 
solution  in  terms  of  indigotin.  Then  dilute  so  that  it  requires 
25-30  cc.  to  decolorize  100  cc. 
of  the  standard  indigotin  solu- 
tion. Retitrate  this  corrected 
solution  and  determine  the  exact 
strength  in  terms  of  indigotin. 
Before  making  the  final  titra- 
tion, place  the  hydrosulfite  solu- 
tion in  a  2-liter  bottle  and  pour 
in  sufficient  benzol  to  form  a 
layer  1-2  cm.  deep  to  exclude 
the  air.  Also  connect  up  the 
bottle  so  that  a  stream  of  illu- 
minating gas  can  be  passed  into 
it.  (See  Fig.  4.) 

TITRATION  OF  SULFONATED 
SAMPLE. — Pipette  into  the  titrat- 
ing flask  an  aliquot  of  the  solu- 
tion prepared  as  described  under 
"  sulfonation  "  which  will  cor- 
respond to  about  0.1  gram  of 
indigotin,  and  titrate  with  the 
hydrosulfite  solution  exactly  as  in 

the  standardization.  This  should  require  at  least  25  cc.  of  hydro- 
sulfite solution.  If  less  is  required,  repeat  using  a  larger  aliquot. 
Always  run  the  titration  in  duplicate. 

NOTE. — The  titration  must  be  made  as  rapidly  as  possible  and  at  the  same 
time  great  care  must  be  used  not  to  overrun  the  end  point.  If  the  titration  is 
carried  out  too  slowly,  there  is  danger  of  the  indigo  solution  oxidizing  back  to 
indigo  blue  and  the  results  will  be  too  high.  With  a  little  experience  there 
should  not  be  much  difficulty  in  determining  the  end  point,  especially  with 
synthetic  indigoes,  but  with  the  impure  natural  indigoes  there  is  apt  to  be 
some  trouble  in  determining  the  exact  end  point  and  it  is  best,  especially  if 
one  is  not  used  to  the  titration,  to  run  several  titrations  and  report  the  average. 

Mineral  Matter  (Ash). — Weigh  accurately  1  gram  of  the  dried 
powder  into  a  platinum  dish  and  ignite  gently  until  all  organic 


FIG.  4. — Apparatus  for  Titrating 
Indigotin. 


100  TECHNICAL  METHODS  OF  ANALYSIS 

matter  is  burned  off.  As  calcium  carbonate  is  generally  present 
care  should  be  taken  not  to  ignite  sufficiently  to  drive  off  the  CC^ 
For  more  accurate  work  blast  the  ash,  determine  quantitatively 
the  CaO,  calculate  it  to  CaCOs  and  correct  the  mineral  matter 
accordingly. 

REFERENCE. — Badische  Anilin-  u.  Soda-Fabrik:  "Indigo  Pure,"  page  26. 

NICOTINE  IN  TOBACCO  AND  TOBACCO  EXTRACT 

General. — The  samples  should  be  analyzed  as  received  as  any 
attempt  at  artificial  drying  is  likely  to  cause  loss  of  nicotine.  (If 
the  tobacco  is  too  moist  to  be  ground  it  may  be  dried  at  a  tem- 
perature not  exceeding  60°  C.)  The  material  should  be  ground 
so  as  to  pass  through  a  No.  20  sieve  or  finer. 

Kissling  Method.* — (A)  SOLUTIONS  REQUIRED. — (a)  Alcoholic 
NaOH. — Dissolve  6  grams  of  NaOH  in  40  cc.  of  water  and  60  cc. 
of  90%  alcohol. 

(6)  0.4%  Sodium  Hydroxide. — Dissolve  4  grams  of  NaOH  in 
1  liter  of  water. 

(c)  Sulfuric  Acid. — Approximately  0.1   N  solution,  carefully 
standardized. 

(d)  Phenacetolin  Solution. — Make  a  0.5%  solution  in  alcohol. 

(e)  Cochineal  Solution. — Digest  with  frequent  agitation  3  grams 
of  pulverized  cochineal  in  a  mixture  of  50  cc.  of  95%  alcohol  and 
200  cc.  of  water  for  one  or  two  days  at  room  temperature  and 
then  filter. 

(B)  DETERMINATION. — Weigh  into  a  small  beaker  5-6  grams  of 
tobacco  extract  or  20  grams  of  finely  powdered  tobacco,  previously 
dried  at  60°  C.,  if  necessary.  Add  10  cc.  of  the  alcoholic  NaOH 
solution  and  follow,  in  the  case  of  tobacco  extract,  with  enough 
pure  powdered  CaCOs  to  form  a  moist  but  not  lumpy  mass.  Mix 
the  whole  thoroughly.  Transfer  to  a  Soxhlet  extractor  and  ex- 
haust for  about  five  hours  with  ether.  Evaporate  the  ether  at  a 
low  temperature,  and  take  up.  the  residue  with  50  cc.  of  the  0.4% 
NaOH  solution.  Transfer  this  residue  by  means  of  water  to  a 
500  cc.  Kjeldahl  flask,  and  distill  with  steam,  using  a  condenser 
through  which  water  is  flowing  rapidly.  Use  a  3-bend  outflow 

*  Official  method  of  the  Assoc.  of  Official  Agr.  Chemists;  see  its  Journal, 
II,  Methods  of  Analysis  (1916),  page  73. 


GENERAL  ORGANIC  ANALYSES  iVj  ;  ', 


tube  and  a  few  pieces  of  pumice  and  a  small  piece  of 
prevent  bumping  and  frothing.  Continue  distillation  till  all  the 
nicotine  has  passed  over,  the  distillate  usually  varying  from  400 
to  500  cc.  When  completed,  only  about  15  cc.  of  the  liquid 
should  remain  in  the  distillation  flask.  Titrate  the  distillate  with 
0.1  N  H2SO4,  using  phenacetolin  or  cochineal  as  indicator.  One 
molecule  of  H2S04  is  equivalent  to  2  molecules  of  nicotine. 

CALCULATION.  —  1  cc.  0.1  N  acid  =  0.01622  gram  nicotine 
(Ci0H14N2). 

Silicotungstate  Method  *  (Bertrand  and  Javillier).  —  Distill  in  a 
current  of  steam  as  in  the  Kissling  method  and  precipitate  the 
nicotine  from  the  distillate  as  nicotine-silicotungstate,  a  rose-white 
salt  with  the  following  formula: 

2Ci0Hi4N2  -  2H2OSiO2  •  12WO3  •  5H2O. 

This  salt  on  being  ignited  leaves  a  residue  of  Si02  and  WOs,  from 
which  is  calculated  the  weight  of  nicotine  originally  present. 

(A)  REAGENTS.  —  (a)  Silicotungstic  Add  Solution.  —  Prepare  a 
12%  solution  of  the  silicotungstic  acid  having  the  following  for- 
mula :  4H2OSi02  •  12W03  •  22H2O. 

(b)  Sodium  or  Potassium  Hydroxide  Solution  (1  :  2). 

(c)  Dilute  Hydrochloric  Acid  (1  :  4). 

(B)  DETERMINATION.  —  Weigh  such  an  amount  of  the  prep- 
aration as  will  contain  preferably  between  0.1  and  1.0  gram  of 
nicotine  (if  the  sample  contains  very  little  nicotine,  about  0.1%, 
do  not  increase  the  amount  to  the  point  where  it  interferes  with  the 
distillation)  ;  wash  with  water  into  a  500  cc.  round-bottomed  dis- 
tillation flask;  add  a  little  paraffin  to  prevent  frothing,  a  few  small 
pieces  of  pumice  and  a  slight  excess  of  the  NaOH  or  KOH  solution, 
using  phenolphthalein  as  an  indicator.     Distill  rapidly  in  a  cur- 
rent of  steam  through  a  well-cooled  condenser,  connected  by  an 
adaptor  with  a  suitable  flask  containing  10  cc.  of  the  dil.  HC1. 
When  distillation  is  well  under  way,  heat  the  distillation  flask  to 
reduce  the  volume  of  the  liquid  as  far  as  practicable  without  bump- 
ing or  undue  separation  of  insoluble  matter.     Distill  until  a  few 
cc.  of  the  distillate  show  no  cloud  or  opalescence  when  treated 

*  Official  method  of  the  Assoc.  of  Official  Agr.  Chemists;  see  its  Journal, 
II,  Methods  of  Analysis  (1916),  page  74. 


102,         >  t    ;  TECHNICAL  METHODS  OF  ANALYSIS 

w?th  ^  drop,  of  silicotungstic  acid  and  a  drop  of  the  dil.  HC1. 
Confirm  the  alkalinity  of  the  residue  in  the  distillation  flask  with 
phenolphthalein.  Make  up  the  distillate,  which  may  amount 
to  1000-1500  cc.  to  a  convenient  volume  (the  solution  may  be 
concentrated  on  the  steam  bath  without  loss  of  nicotine),  mix 
well  and  pass  through  a  large  dry  filter  if  not  clear.  Test  a  por- 
tion with  methyl  orange  to  assure  its  acidity.  Pipette  an  aliquot, 
containing  about  0.1  gram  of  nicotine,  into  a  beaker  (if  the  sam- 
ples contain  very  small  amounts  of  nicotine,  an  aliquot  containing 
as  little  as  0.01  gram  of  nicotine  may  be  used),  add  to  each  100  cc. 
of  liquid  3  cc.  of  the  dil.  HC1,  or  more  if  the  necessity  is  indicated 
by  the  test  with  methyl  orange,  and  add  1  cc.  of  silicotungstic 
acid  solution  for  each  0.01  gram  of  nicotine  supposed  to  be  present. 
Stir  thoroughly  and  let  stand  overnight.  Before  filtering,  stir 
the  precipitate  to  see  that  it  settles  quickly  and  is  in  crystalline 
form;  then  filter  on  an  ashless  filter  paper,  and  wash  with  cold  dil. 
HC1  (1  :  1000).  Transfer  the  paper  and  precipitate  to  a  weighed 
platinum  crucible,  dry  carefully,  and  ignite  until  all  carbon  is 
destroyed.  Finally  heat  over  a  Teclu  or  Meker  burner  for  not  more 
than  ten  minutes.  The  weight  of  the  residue  multiplied  by  0.114 
gives  the  weight  of  nicotine  present  in  the  aliquot. 

Ash. — Incinerate  2  grams  of  the  sample  in  a  weighed  platinum 
dish.  Moisten  with  water,  dry  and  again  ignite.  Repeat  until  no 
more  particles  of  carbon  remain.  Cool  in  a  desiccator  and  weigh. 

Dissolve  the  ash  in  hot  water  and  filter.  Save  the  filtrat<~. 
Ignite  and  weigh  the  water-insoluble  ash.  Cool  the  filtrate  and 
titrate  with  0.1  N  acid  and  methyl  orange.  Report  the  alkalinity 
of  the  water-soluble  ash  as  the  number  of  cc.  of  0.1  N  acid  required 
to  neutralize  the  water-soluble  ash  from  1  gram  of  the  sample. 

Dissolve  the  water-insoluble  ash  in  25  cc.  of  0.5  N  HC1  and 
titrate  the  excess  with  0.1  N  alkali  and  methyl  orange.  Deduct 
the  number  of  cc.  of  0.1  N  alkali  from  125  and 'divide  by  2.  This 
will  give  the  alkalinity  of  the  water-insoluble  ash  in  the  same 
terms  as  above.  (In  some  cases  it  may  be  necessary  to  use  double 
the  amount  of  0.5  N  acid.  In  that  case  subtract  the  cc.  of  0.1  N 
alkali  from  250  and  divide  by  2.) 

After  titration  of  the  water-insoluble  ash,  add  cone.  HC1  and 
boil.  Filter  the  bulk  of  the  solution  through  an  ashless  filter  and 
add  cone.  HC1  to  the  residue.  Warm,  dilute,  and  filter  through 


GENERAL  ORGANIC  ANALYSES  103 

the  same  filter.  Wash  with  distilled  water,  ignite,  and  weigh  as 
"  hydrochloric  acid-insoluble  ash." 

NOTES. — (1)  Cigarette  tobacco  contains  about  1.0-3.3%  of  nicotine  (av. 
about  1.7%),  cigars  about  1.5%,  chewing  tobacco  about  1.1%. 

(2)  Cigarette  papers.  Nearly  all  cigarette  papers  have  chemical  fillers, 
presumably  to  improve  their  burning  qualities  and  color.  These  generally 
consist  of  carbonates  and  oxides  of  Al,  Ca  and  Mg.  The  best  papers  are 
made  from  pure  linen  sized  with  starch.  A  little  KNOs  is  also  sometimes 
added. 

REFERENCE.  —  Azor  Thurston:  "Analysis  of  Cigarettes,  Cigars  and 
Tobacco."  Bulletin  No.  2,  Agr.  Commission  of  Ohio,  Dairy  and  Food  Div., 
Bureau  of  Drugs,  Nov.,  1914. 


NICOTINE  SOLUTION 

General. — This  method  is  for  the  analysis  of  nicotine  solutions 
for  use  in  preparing  specially  denatured  alcohol  according  to 
Formula  No.  4.  The  tobacco  denaturant  must  conform  to  the 
following  analytical  requirements: 

Determination  of  Nicotine. — Measure  20  cc.  of  the  solution 
into  a  special  250  cc.  dephlegmating  flask  (Fig.  5)  ;*  add  10  cc.  of 
0.1  N  KOH;  make  the  liquid  up  to  50  cc.  and  distill  in  a  current  of 
steam  until  the  distillate  is  no  longer  alkaline  (about  500  cc.). 
Wash  the  distillate  into  a  700  cc.  flask  and  fill  two  other  flasks 
with  the  same  amount  of  distilled  water.  Add  8  drops  of  resa- 
zurin  solution  f  to  each  flask  as  an  indicator,  and  add  1  drop  of 
0.1  N  acid  to  one  blank  and  1  drop  of  0.1  N  alkali  to  the  other. 
This  should  give  in  the  case  of  the  acid  solution  a  pink  coloration 
and  in  the  case  of  the  alkali  solution  a  blue  coloration  by  trans- 
mitted light.  Then  titrate  the  nicotine  distillate  with  0.1  N 
H2SO4  and  make  comparisons  with  the  2  blanks  until  the  nicotine 
distillate  shows  an  end  point  of  all  red  and  no  blue  on  transmitted 
light.  This  end  point  is  difficult  to  detect  without  some  practice 
and  it  should  be  approached  with  care.  The  best  way  to  observe 
the  final  end  point  is  to  place  all  three  flasks  in  a  line  on  white 

*  United  States  Internal  Revenue  Regulations  No.  30  specifies  a  Kjeldahl 
flask  fitted  with  a  suitable  bulb  tube,  but  we  have  found  the  special  flask 
more  convenient  and  equally  accurate. 

f  Resazurin  Solution:  Dissolve  0.2  gram  of  the  crystals  in  distilled  water, 
add  40  cc.  of  0.1  N  NH3  solution  and  dilute  to  1  liter. 


104 


TECHNICAL  METHODS  OF  ANALYSIS 


paper  and  have  a  sheet  of  white  paper  back  of  them.  A  com- 
parison of  color  can  be  made  much  more  easily  in  this  way.  Not 
less  than  23.2  cc.  of  0.1  N  H2S04  should  be  required  for  the  neu- 
tralization. (This  is  equivalent  to  1.88%  of  nicotine,  which  is 
the  minimum  amount  that  is  demanded  in  the  tobacco  denaturant.) 
CALCULATION.— 

0  16218 
Cc.  of  0.1  N  H2S04  required  X—        — =per  cent  of  nicotine. 


Fio.  5. — Flask  for  Nicotine  Determination. 

Test  of  Coloring  Matter. — The  original  formula  for  nicotine 
denaturant  required  that  it  be  colored  with  a  mixture  of  blue  and 
yellow  dyes,  thus  giving  a  green  solution.  On  August  11,  1916, 
due  to  the  scarcity  of  dyestuffs,  the  Treasury  Department  ruled 
that  the  yellow  dye  may  be  omitted  and  the  denaturant  colored 
only  with  methylene  blue. 

In  case  the  denaturant  is  of  a  green  color,  proceed  as  follows 
for  the  test  of  coloring  matter: 

Take  1  cc.  of  the  denaturant  and  make  up  to  100  cc.  with  water, 
acidulating  with  a  few  drops  of  H2SO4.  Immerse  in  this  solution 
a  piece  of  white  cotton  cloth  and  boil  the  solution.  Continue 
the  process,  adding  more  cloth  and  more  water  if  necessary,  until 


GENERAL  ORGANIC  ANALYSES  105 

all  the  blue  color  in  the  solution  is  fixed  on  the  cloth.  Then  add  a 
piece  of  white  woolen  cloth  and  boil  the  bath  as  before  until  all 
the  yellow  color  is  fixed  upon  the  cloth.  Both  the  cotton  and 
woolen  cloths  should  show  decided  colors — the  cotton  blue  and  the 
woolen  yellow. 

If  the  denaturant  is  blue,  no  dyeing  test  is  required. 

Intensity  of  Color. — If  the  denaturant  is  green,  it  must  contain 
sufficient  coloring  matter  so  that  when  observed  in  an  eighth-inch 
cell  of  Levibond's  tintometer  it  will  show  a  color  of  an  intensity 
not  less  than  No.  24  yellow  combined  with  No.  3  blue. 

If  the  denaturant  is  blue,  proceed  as  follows:  Dilute  1  cc.  of 
the  denaturant  material  with  100  cc.  of  water  and  compare  50  cc. 
of  this  solution  in  a  50  cc.  Nessler  tube  with  50  cc.  of  a  solution 
containing  5  grams  of  c.  P.  copper  sulfate  (OuSC^-SH^O)  in  100  cc. 
of  water.  The  color  of  the  diluted  nicotine  solution  should  be 
at  least  as  intense  as  that  of  the  copper  solution. 

NOTES. — (1)  The  original  regulations  called  for  the  use  of  rosolic  acid  as 
indicator.  Resazurin,  however,  gives  a  better  end  point  and  hi  a  letter  from 
the  Commissioner  of  Internal  Revenue  at  Washington,  dated  September  4, 
1913,  the  use  of  the  latter  was  sanctioned. 

(2)  Resazurin  crystals  are  made  by  Theodore  Schuchardt,  Corlits,  Ger- 
many, and  may  be  obtained  from  Eimer  &  Amend,  New  York,  N.  Y. 

REFERENCES. — Regulations  No.  30  Revised,  United  States  Internal  Rev- 
enue—July 15,  1907.  Treasury  Decision  (1223),  September  5,  1907. 


CHAPTER  IV 
ANALYSIS  OF  METALS 

SAMPLING  IRON  AND  STEEL 

General. — Select  at  random  a  sufficient  number  of  bars,  rods, 
rails,  I-beams,  or  car  axles,  etc.,  as  the  case  may  be,  to  represent 
the  shipment  and  carefully  mark  them.  From  each  of  these  pieces 
procure  a  sample  composed  of  mixed  borings  weighing  between 
1  and  2  ounces. 

Location  of  Borings. — In  order  to  eliminate  as  far  as  possible 
the  effect  of  possible  segregation,  take  the  borings  at  different 
points  of  the  piece,  selection  being  made  with  reference  to  the 
rapidity  with  which  the  different  portions  may  have  cooled.  This 
is  preferably  done  on  a  cross-section  of  the  piece.  For  example 
in  sampling  a  steel  rail,  make  one  boring  close  to  the  outside  of 
the  head,  one  at  the  center  of  the  head,  another  at  the  middle  of 
the  web,  and  one  near  the  center  of  the  foot.  Where  access  to  a 
cross-section  is  impossible,  take  borings  from  the  outside  which 
will  represent  as  nearly  as  possible  the  desired  locations. 

Cleaning  the  Surface. — When  borirgs  are  to  be  made  from  a 
longitudinal  surface,  remove  all  rust  and  scale  by  means  of  an 
emery  wheel,  emery  cloth,  or  other  abrasive;  in  no  case,  however, 
should  any  considerable  portion  of  the  first  borings  be  discarded. 
When  drilling  into  a  cross  section,  discard  enough  of  the  borings 
to  insure  absence  of  rust  or  dirt  from  the  portion  taken. 

Size  of  Borings. — In  order  that  a  perfect  rr  ixing  of  the  samples 
from  different  parts  of  the  piece  may  be  pcssitle,  it  is  desirable 
to  have  borings  in  the  form  of  small  thin  chips,  rather  than  long, 
spiral  turnings.  This  may  be  accomplished  by  slightly  dulling 
the  cutting  edge  of  a  half-inch  twist  drill  or  by  using  a  half-inch 
flat  drill. 

Freedom  from  Contamination. — It  is  absolutely  essential  that 
the  utmost  care  be  taken  to  prevent  contamination  of  the  sample 

106 


ANALYSIS  OF  METALS  107 

with  grease,  oil,  or  dirt  of  any  kind.  Brush  the  piece  of  iron  or 
steel  to  be  sampled  free  from  any  loose  material  which  may  adhere 
to  it;  collect  the  borings  on  a  clean  white  sheet  of  paper.  Use  no 
oil,  grease,  or  other  lubricating  substance  on  the  drill. 

Place  the  combined  borings  from  each  piece  in  clean,  wide- 
mouthed,  glass-stoppered  bottles;  stopper  tightly  and  carefully 
mark  each  bottle  for  identification. 

CARBON  STEEL 

General. — This  method  covers  the  analysis  of  plain  carbon 
steels,  i.e.,  those  containing  only  C,  Mn,  P,  Si  and  S. 

In  those  cases  where  an  alternative  method  is  given,  the  latter 
is  to  be  used  only  when,  on  account  of  lack  of  chemicals  or  appa- 
ratus, the  first  method  cannot  be  employed. 

Preparation  of  Sample. — The  points  to  be  observed  in  sampling 
steel  for  analysis  are  as  follows: 

(1)  Samples  must  be. drillings  or  chips  cut  by  some  machine 
tool  without  the  application  of  water,  oil,  or  other  lubricant,  and 
free  from  scale,  grease,  dirt  or  other  foreign  substance.     If  sam- 
ples are  taken  by  drilling,  the  diameter  of  the  drill  should  be  not 
less  than  0.5  nor  more  than  0.75  inch. 

(2)  Samples  must  be  uniformly  fine  and  well  mixed  before 
analysis. 

(3)  If  the  composition  of  the  surface  of  a  sample  piece  has 
been  altered  by  case  hardening  or  decarbonization,  do  not  include 
in  the  sample  for  analysis  drillings  which  represent  this  outer 
surface. 

(4)  Heat-treated  samples  should  be  annealed  before  sampling. 

(5)  Round  or  flat  samples  up  to  and  including  1  inch  in  thick- 
ness must  be  drilled  through  the  entire  thickness  of  metal;    or, 
if  the  sample  is  taken  on  a  milling  machine,  it  must  be  taken  by 
machining  off  the  entire  cross  section. 

(6)  From  material  having  a  cross  section  larger  than  1  inch 
samples  should  be  taken  at  any  point  midway  between  the  outside 
and  the  center  by  drilling  parallel  to  the  axis.     If  this  is  not  prac- 
ticable, the  piece  may  be  drilled  on  its  side,  but  do  not  collect  the 
drillings  until  they  represent  the   above-named   portion   of  the 
sample. 


108 


TECHNICAL  METHODS   OF  ANALYSIS 


(7)  Whenever  a  sample  is  received  in  the  form  of  drillings, 
they  should  always  be  examined  for  oil  and  other  foreign  matter. 
Any  oil  must  be  completely  removed  with  ether  and  the  drillings 
then  thoroughly  dried.  If  foreign  particles  are  present,  go  over 
the  sample  with  a  magnet  and  use  only  that  portion  for  analysis 
which  is  picked  up  by  it. 

Total  Carbon. — Determine  carbon  by  direct  combustion  in  the 
electric  furnace.  The  general  arrangement  of  the  combustion 
apparatus  is  as  follows  (see  Fig.  6) : 


h    g 


FIG.  6. — Apparatus  for  Determining  Carbon  in  Steel. 

(a)  Oxygen  tank. 

(6)  Safety  jar  for  H2SO4. 

(c)  CaCl2jar. 

(d)  Soda-lime  jar. 

(e)  Raskins'  multiple  tube  electric  furnace. 
(/)  U-tube  for  granular  Zn. 

(g)  U-tube  for  CaCl2. 

(h)  Soda-lime  absorption  tube  for  CO2. 

(f)  Bottle  for  Ba(OH)2  solution   (exhaustion  and  gas  speed 
indicator). 

The  combustion  apparatus  should  be  tested  for  leaks  from 
time  to  time  (see  Blair:  "  Chemical  Analysis  of  Iron,"  page  138, 
Fig.  63).  Before  weighing  the  absorption  tubes  in  the  morning 


ANALYSIS  OF  METALS  109 

connect  them  to  the  combustion  apparatus  and  pass  oxygen 
through  for  ten  minutes,  weigh  and  again  pass  oxygen  through 
for  thirty  minutes  and  weigh.  This  should  be  continued  until 
the  weight  is  constant. 

For  steels  containing  0.30-1.50%  carbon,  take  2  grams  of 
fine  drillings  not  over  0.25  mm.  thick.  For  lower  percentages  of 
C,  take  3-5  grams  of  drillings 'bet ween  20-  and  60-mesh  size.  Trans- 
fer the  sample  to  an  alundum  or  clay  boat,  protected  by  a  layer 
of  ignited  A^Os  or  alundum.  Place  the  drillings  in  as  compact  a 
mass  as  possible.  If  curly  drillings  are  scattered  along  the  entire 
length  of  the  boat  instead  of  being  put  in  a  deep,  compact  body, 
borings  that  are  a  little  thick  will  frequently  be  found  to  contain 
still  unburned  metal.  Drillings  lying  in  close  contact  heat  each 
other  to  incandescence  during  burning  with  oxygen. 

Introduce  the  boat  with  the  charge  into  the  center  of  the 
combustion  tube,  maintained  at  a  temperature  of  1000°  C.  Admit 
oxygen  at  the  rate  of  25  bubbles  per  ten  seconds  or  250  cc.  every 
ten  minutes.  As  soon  as  the  steel  begins  to  burn,  there  is  at 
first  a  rapid  evolution  of  gas,  which  quickly  ceases.  When  oxida- 
tion of  the  charge  is  completed,  oxygen  begins  to  flow  at  normal 
speed  again.  Allow  thirty  minutes  for  oxidation  of  the  sample 
and  sweeping  of  all  C02  from  the  combustion  tube  into  the  absorp- 
tion apparatus. 

Weigh  the  absorption  tube  and  from  the  weight  of  CO2  calcu- 
late the  per  cent  of  C  in  the  sample. 

Wt.  of  C02 

CALCULATION. — —  X  27.28  =  per  cent  C. 

Wt.  of  sample 

NOTES. — (1)  In  case  of  very  heavy  drillings,  those  that  will  not  pass  a  20- 
mesh  sieve,  the  analysis  should  be  made  by  solution.  Dissolve  2-5  grams  of 
steel,  using  75  cc.  per  gram  of  a  solution  of  copper  potassium  chloride.  Follow 
the  procedure  described  for  the  determination  of  Total  Carbon  in  Pig  and 
Cast  Iron  on  page  130.  This  method,  however,  is  not  reliable  for  alloy  steels 
and  should  be  used  on  plain  steels  only  when  drillings  cannot  be  burned 
3ompletely  by  direct  combustion. 

(2)  After  refilling  the  CaCl2  U-tube  (g)  the  contents  should  be  saturated 
with  CO2,  as  the  fresh  drier  may  absorb  CO2  and  thereby  cause  lower  results 
it  first. 

(3)  Soda-lime  should  be  hydroxides  of  Na  and  Ca.     The  most  satisfactory 
soda-lime  for  carbon  combustions  in  steel  is  12-mesh  size  and  contains  15% 
)f  H20. 

(4)  Soda-lime  absorption   tubes  should  be  filled   three-quarters  full  with 


110  TECHNICAL  METHODS  OF  ANALYSIS 

soda-lime    and   the   remainder   with    CaCl2.     The    CaCl2  will    absorb   any 
moisture  which  might  be  liberated  by  the  soda-lime  during  absorption- of  CO2. 

(5)  Soda-lime  tubes  will  absorb  from  0.6-0.7  gram  of  CO2  before  it  is 
necessary  to  renew  the  chemicals.     Saturation  will  be  indicated  by  precipita- 
tion of  BaCO3  in  the  Ba(OH)2  solution  (i). 

(6)  The  same  grade  of  CaCl2  and  of  soda-lime  should  be  used  in  the  train 
preceding  and  following  the  combustion  furnace. 

Graphitic  Carbon. — Weigh  10  grams  of  steel  in  a  200  cc.  beaker 
and  add  150  cc.  of  HNOs  (1  :  3).  Heat  the  beaker  on  the  steam 
bath  until  the  steel  is  all  dissolved.  Filter  on  a  loose-bottom 
Gooch  crucible  through  asbestos  and  wash  with  water,  HC1 
(1:1),  H20,  NH4OH  (1%),  H20,  HC1  (1  :  1),  H20,  and  again 
H2O.  Dry  for  one  hour  at  100°  C.  Transfer  the  asbestos  with 
the  carbon  to  the  combustion  boat  and  determine  the  carbon  as 
under  total  carbon. 

Combined  Carbon. — This  is  the  difference  between  the  total 
and  the  graphitic  carbon. 

Manganese  (Bismuthate  Method). — Titration  with  sodium 
arsenite  (Method  I,  below)  is  sufficiently  accurate  for  ordinary  pur- 
poses. In  case  of  disputes,  however,  or  where  extreme  accuracy  is 
desired,  the  titration  should  be  made  with  ferrous  ammonium 
sulfate  and  KMnCU  (Method  II).  The  procedure  up  to  the 
point  of  titration  is  the  same  in  either  case,  as  follows:  Dissolve 
exactly  1  gram  of  drillings  in  50  cc.  of  HNO3  (1  :  3)  in  a  200  cc. 
Erlenmeyer  flask,  cool  and  add  about  0.5  gram  of  sodium  bis- 
muthate.  Boil  until  the  pink  color  has  disappeared  and  dissolve 
any  precipitate  of  MnO2  by  adding  a  few  drops  of  a  saturated 
solution  of  FeS04  or  of  Na2S2Os;  then  heat  until  all  nitrous 
oxide  fumes  have  been  driven  off,  cool  to  60°  F.,  add  1  gram  of  Na 
bismuthate  and  shake  the  flask  vigorously  for  a  few  minutes. 
Add  50  cc.  of  3%  HNOs*  and  filter  the  solution  into  a  suction 
flask  through  an  extra  porous  alundum  thimble.  The  thimble 
should  not  be  filled  so  full  that  any  of  the  solution  comes  in  con- 
tact with  the  rubber  connection.  Wash  with  50-100  cc.  of  the 
same  acid  and  finally  with  water.  Titrate  the  filtrate  by  one  of 
the  following  methods: 

*  This  3%  HNO3  should  be  prepared  by  adding  60  cc.  of  cone.  HNO3 
to  1940  cc.  of  H2O;  then  add  4  or  5  grams  of  bismuthate,  shake  and  let  stand 
overnight  before  using.  This  destroys  lower  oxides  of  nitrogen  which  have  a 
tendency  to  cause  low  results. 


ANALYSIS  OF  METALS  111 

METHOD  I. — Titrate  the  filtrate  in  the  flask  with  standard 
sodium  arsenite  solution  until  2  drops  produce  no  further  change 
in  color.  Until  the  end  point  is  reached,  the  arsenite  solution  will 
produce  a  clear  spot  where  it  strikes  the  liquid. 

Sodium  Arsenite  Solution. — For  each- liter  dissolve  2.5  grams  of 
anhydrous  Na2COs  in  distilled  water,  add  1  gram  of  c.  P.  As20s 
to  the  hot  Na2COs  solution  and  boil  until  the  As2Os  is  dissolved. 
Cool  and  dilute  to  1  liter. 

STANDARDIZATION. — Measure  into  a  300  cc.  Erlenmeyer  flask 
exactly  20  cc.  of  0.05  N  KMnO4  solution.  Dilute  to  150  cc.,  add 
15  cc.  of  cone,  water-white  HNOs  and  titrate  with  arsenite  solution 
in  the  same  manner  as  above.  Make  the  standardization  in 
triplicate,  and  if  agreement  is  satisfactory,  take  the  average.  Cal- 
culate the  Mn  factor  of  the  solution. 

0.0110 

CALCULATION. — Mn  factor  = . 

cc.  of  arsenite  used 

METHOD  II. — Add  to  the  filtrate  in  the  flask  an  excess  of  stand- 
ard ferrous  ammonium  sulfate  solution,  then  titrate  back  the 
excess  with  0.05  N  KMnQt  solution  to  the  appearance  of  a  faint 
permanent  pink  color. 

CALCULATION. — Run  a  blank,  exactly  as  in  the  regular  deter- 
mination, to  obtain  the  equivalent  of  the  KMnCX  solution  in  terms 
of  the  ferrous  ammonium  sulfate  solution. 

Subtract  the  number  of  cc.  of  KMnCX  solution  used  in  the 
back  titration  from  the  KMnQi  equivalent  of  the  ferrous  ammo- 
nium sulfate  added.  This  gives  the  volume  of  KMnO*  required 
by  the  Mn  in  the  sample,  which,  multiplied  by  the  Mn  factor  of 
the  KMnOi,  gives  the  amount  of  Mn  in  the  sample. 

Standard  Solutions. — (a)  0.05  N  KMnCU:  Dissolve  1.58  grams 
of  pure  KMnO4  in  water  and  dilute  to  1  liter. 

(b)  Ferrous  Ammonium  Sulfate:  Dissolve  20  grams  of 
Fe(NH4)2(SO4)2-6H20  in  water,  add  50  cc.  of  cone.  H2S04  and 
dilute  to  1  liter. 

STANDARDIZATION. — Standardize  the  KMnCU  solution  against 
standard  sodium  oxalate  of  the  U.  S.  Bureau  of  Standards  as 
follows:  In  a  300  cc.  Erlenmeyer  flask  dissolve  0.150  gram  of 
sodium  oxalate  in  125  cc.  of  hot  water  (80-90°  C.)  and  add  10  cc. 
of  H2SO4  (1:1).  Titrate  at  once  with  0.05  N  KMn04,  stirring 


112  TECHNICAL  METHODS  OF  ANALYSIS 

the  liquid  vigorously  and  continuously.  The  KMn(>4  must  not 
be  added  more  rapidly  than  10-15  cc.  per  minute,  and  the  last 
0.5-1  cc.  must  be  added  dropwise,  with  particular  care  to  allow 
each  drop  to  be  fully  decolorized  before  the  next  is  added.  The 
solution  should  not  be  below  60°  C.  when  the  end  point  is  reached. 

0.0246 

CALCULATION. — Mn  f actor  = T      •  ^ -. 

cc.  KMnO*  used 

If  the  Fe  factor  of  the  KMn04  has  already  been  determined 
against  Na2C2Oi  as  above,  the  Mn  factor  may  be  calculated  from 
the  Fe  factor  by  multiplying  the  latter  by  0.1967. 

Phosphorus. — Dissolve  2  grams  of  the  sample  in  a  500  cc. 
Erlenmeyer  flask  in  60  cc.  of  HN03  (1  :  3).  To  the  boiling  solution, 
free  from  red  fumes,  add  5  cc.  of  saturated  KMnO4  solution.  Con- 
tinue boiling  until  the  pink  color  disappears.  If  no  precipitate  of 
brown  oxide  of  manganese  remains,  add  a  little  more  KMnOi. 
When  a  permanent  brown  precipitate  does  remain,  cool  the  flask 
and  add  a  crystal  of  tartaric  acid.  Boil  this  solution  until  clear, 
remove  the  flask  from  the  hot  plate  and  after  two  or  three  minutes 
add  15  cc.  of  cone.  NILiOH.  Bring  back  with  a  little  HNO3  if  a 
precipitate  of  Fe(OH)3  remains.  Warm  to  80°  C.,  add  60  cc. 
of  molybdate  solution  and  shake  five  minutes.  Let  stand  0.5 
hour,  or  until  the  precipitate  settles.  Filter  at  once  through  an 
11  cm.  filter  paper,  wash  the  yellow  precipitate  five  times  with 
2%  HN03,  then  with  1%  KN03  solution  (NaN03  must  not  be 
used)  until  free  from  add  (approximately  15  times). 

Place  the  filter  and  contents  in  the  original  flask,  which  has 
been  thoroughly  rinsed  with  water,  add  approximately  50  cc.  of 
cold  distilled  water  and  a  measured  excess  of  standard  NaOH 
from  a  burette,  5  cc.  at  a  time,  in  sufficient  amount  to  completely 
dissolve  the  yellow  precipitate.  Cork  the  flask  and  agitate  vio- 
lently until  the  filter  paper  is  disintegrated.  Add  3  drops  of  1% 
phenolphthalein  solution  with  a  medicine  dropper  and  titrate 
with  standard  HNO3  to  the  disappearance  of  the  pink  color. 

CALCULATION. — Run  a  blank  titration  the  same  way  as  in  the 
regular  determination  to  obtain  the  value  of  the  NaOH  solution 
in  terms  of  the  HNO3  solution.  Subtract  the  number  of  cc.  of 
HN03  used  from  the  number  corresponding  to  the  volume  of 
NaOH  added.  The  difference  is  the  cc.  of  HNO3  equivalent  to 
the  P  in  the  sample.  This  multiplied  by  the  value  of  the  HNOs 


ANALYSIS  OF  METALS  113 

in  terms  of  P  gives  the  weight  of  P  in  the  sample.     This  weight 
divided  by  the  weight  of  steel  taken  X 100  =  per  cent  P. 

SOLUTIONS. — (A)  Molybdate  Solution: 

(1)  151  grams  of  MoO3  (85%); 
600  cc.  of  water; 

150  cc.  of  NH4OH  (cone). 

(2)  1000  cc.  of  water; 

675  cc.  of  HNOs  (cone.); 
800  cc.  of  solution  (1). 

To  prepare  solution  (1)  pour  all  of  the  MoOs  into  the  water. 
Shake  to  get  in  suspension  and>  before  it  settles,  quickly  pour  the 
NH4OH  into  the  bottle.  Shake  until  the  powder  is  dissolved. 
To  prepare  solution  (2)  mix  the  acid  and  water  and  cool  thoroughly. 
Then  by  means  of  a  funnel  pour  in  rapidly  all  of  solution  (1). 
Shake  and  add  a  few  crystals  of  sodium  or  ammonium  phos- 
phate. Shake  and  let  stand  overnight  before  using.  Use  only 
the  clear  supernatant  liquid. 

(B)  Standard  Nitric  Acid:    Dilute  10  cc.  of  cone.  HNO3  to 
1  liter.     (The  HNOs  must  be  water  white.) 

(C)  Standard  Sodium  Hydroxide:   Dissolve  8  grams  of  NaOH 
in  400  cc.  of  water,  add  sufficient  Ba(OH)2  solution  to  precipitate 
all  carbonates,  filter  at  once  and  make  up  to  1  liter. 

(D)  1  %  KNOz  Solution  (for  washing) :  10  grams  per  liter. 

(E)  2%  Nitric  Add  (for  washing):   20  cc.  of  cone.  HNOs  per 
liter. 

STANDARDIZATION. — First,  determine  the  strength  of  the 
HN03  in  terms  of  the  NaOH. 

Second,  determine  the  strength  of  the  HNOs  in  terms  of  phos- 
phorus by  titrating  0.5  gram  of  pure  yellow  ammonium  phos- 
phomolybdate  by  the  above  method.  (The  phosphomolybdate 
should  be  dried  for  one  hour  at  100°  C.  before  using.) 

_, ,  0.00825 

CALCULATION — P  f actor  = TTXT/^ j- 

cc.  HN03  used 

The  standard  ammonium  phosphomolybdate  may  be  prepared 
as  follows:  Acidify  a  dilute  solution  of  Na2HPO^  with  HNOs,.  add 
an  excess  of  MoOs  solution,  filter,  wash  the  precipitate  thoroughly 
with  hot  water,  dry  at  150°  C.  and  keep  in  glass-stoppered  vial. 
Determine  the  content  of  phosphorus  by  the  pyrophosphate 


114  TECHNICAL  METHODS  OF  ANALYSIS 

method.*     Pure  ammonium  phosphomolybdate  contains   1.65% 
of  phosphorus. 

NOTES. — See  under  the  Alternative  Method  below. 

Phosphorus  (Alternative  Method).  —  Instead  of  titrating 
the  yellow  precipitate,  filter  on  a  9  cm.  filter  paper  which  has  been 
previously  dried  and  weighed  in  a  glass-stoppered  weighing  bottle. 
Wash  the  precipitate  at  least  5  times  with  2%  HNOa  to  remove 
all  Fe  salts.  Absorb  with  a  blotter  the  excess  of  moisture  from 
the  paper  and  precipitate  and  dry  in  the  oven  at  100°  C.  for  one 
hour.  Weigh  the  paper  and  contents  in  the  weighing  bottle. 
Using  2  grams  of  steel,  the  weight  of  precipitate  in  milligrams 
X  0.00825X100=  per  cent  phosphorus. 

NOTES. — (1)  In  neutralizing  solutions  to  which  NH4OH  has  been 
added,  HNO3  should  be  added  until  the  solution  is  straw  color,  otherwise  a 
small  amount  of  iron  may  separate  causing  high  results. 

(2)  It  is  essential  that  the  yellow  precipitate  be  washed  with  solutions  of 
exactly  the  strength  specified  and  until  free  from  acid. 

(3)  When  running  a  number  of  samples,  the  flask  containing  the  filter 
and  yellow  precipitate  must  be  kept  tightly  corked,  and  alkali  should  not  be 
added  until  the  remainder  of  the  operation  can  be  promptly  carried  through. 

(4)  When  the  alternative  method  of  weighing  the  yellow  precipitate  is 
used,  care  must  be  observed  that  the  filter  paper  is  previously  dried  and 
weighed  in  a  weighing  bottle  and  that  the  final  weight  of  filter  and  contents 
is  made  in  exactly  the  same  manner  as  the  first  weight  of  the  filter. 

Silicon. — Weigh  4  grams  of  steel  into  a  12  cm.  casserole  or 
evaporating  dish  and  add  60  cc.  of  silicon  mixture  (see  below). 
When  effervescence  ceases,  rinse  the  sides  of  the  dish  with  water 
and  cover  with  a  watch  glass.  Place  on  the  hot  plate  and  boil 
slowly  but  continuously  to  dryness.  Bake  to  dehydrate  SiO2, 
and  cool.  Take  up  with  75  cc.  of  HC1  (1  :  3)  and  bring  to  a  boil. 
Keep  at  the  boiling  point  until  the  solution  is  clear.  Filter  while 
hot  through  an  11  cm.  filter,  washing  alternately  with  hot  HC1 
(1:1)  and  hot  water  until  free  from  Fe,  then  wash  the  paper  free 
from  acid.  Ignite  in  a  platinum  crucible  and  weigh  as  SiC^. 
Calculate  to  Si.  (If  the  precipitate  is  red,  volatilize  with  HF.  and 
weigh  again.  The  loss  in  weight  is  SiCb.  Calculate  to  Si.) 

CALCULATION.— SiO2  X  0.4693  =  Si. 

*  Dissolve  a  weighed  amount  of  the  yellow  precipitate  in  NH4OH  and 
precipitate  with  excess  of  magnesia  mixture.  Filter,  ignite  and  weigh  as 
Mg2P2O7.  (See  page  527.) 


ANALYSIS  OF  METALS  115 

Silicon  Mixture. — Into  1500  cc.  of  water  pour  500  cc.  of 
cone.  HNOs,  and  then  150  cc.  of  cone.  H2SO4- 

CAUTION. — Mix  in  the  above  order,  adding  the  H2SO4  very  slowly,  and  let 
cool  before  shaking. 

Sulfur  (Evolution  Method). — Weigh  5  grams  of  steel  into  a 
500  cc.  Florence  flask  provided  with  a  double  perforated  stopper 
carrying  a  2-bulb  safety  tube,  extending  below  the  surface  of  the 
liquid,  and  an  exit  tube  for  gas,  the  latter  connected  to  a  delivery 
tube  extending  to  the  bottom  of  a  tall  glass  tumbler.  Place  30 
cc.  of  CdCl2  solution  in  the  tumbler  and  fill  two-thirds  with  water. 
Add  100  cc.  of  HC1  (1  :  1)  to  the  drillings  in  the  flask.  Place  the 
flask  over  an  Argand  burner,  heat  gently  at  first,  and,  when  the 
drillings  are  dissolved,  boil  until  the  steam  drives  the  last  trace  of 
£[28  from  the  evolution  flask.  Disconnect  the  flask,  add  2  cc.  of 
starch  indicator  *  and  30  cc.  of  cone.  HC1  to  the  solution  in  the 
tumbler,  titrating  at  once  with  standard  iodine  solution  to  the 
appearance  of  a  permanent  blue.  From  the  factor  of  the  iodine 
solution  calculate  the  amount  of  S. 

SOLUTIONS. — (a)  Cadmium  Chloride  Solution:  Dissolve  30 
grams  of  CdCl2  in  300  cc.  of  H2O  and  add  this  to  800  cc.  of 
H2O  and  1200  cc.  of  NH4OH. 

(6)  Iodine  Solution:  Dissolve  4  grams  of  iodine  and  8  grams 
of  KI  in  a  little  H2O  and  make  up  to  1  liter. 

STANDARDIZATION. — The  iodine  solution  should  be  standardized 
against  10  cc.  of  0.1  N  sodium  thiosulfate  solution,  very  accurately 
pipetted  out,  and  the  factor  calculated  so  that  it  will  give  per  cent 
S  on  a  5-gram  sample. 

CALCULATION.— 1  cc.  of  0.1  N  Na2S2O3  =  0.001603  gram  S. 

Then  S  factor  = — — X 10  X  — 

cc.  of  iodine  used  5 

0.003206 


cc.  of  iodine  used 

NOTES. —  (1)  Care  must  be  taken  to  prevent  drillings  from  sticking  to  the 
neck  of  the  wet  flask. 

(2)  When  all  H2S  has  been  driven  over,  the  tube  extending  into  the  tumbler 
will  become  hot  from  condensed  steam,  and  further  heating  should  be  avoided. 

*  See  page  12. 


116  TECHNICAL  METHODS  OF  ANALYSIS 

(3)  In  cases  of  extreme  accuracy  the  aqua  regia  method  should  be  used. 
(See  Blair,  7th  Edition,  page  66.) 

(4)  In  case  of  very  coarse  drillings,  which  dissolve  slowly,  considerable 
acid  will  be  carried  over  and  neutralize  the  NHs  in  the  CdCl2  solution.     In 
such  cases  care  must  be  taken  to  keep  the  solution  up  to  its  original  strength 
in  NHa.     If  such  samples  are  encountered  it  is  preferable  to  use  the  Elliott 
Method  as  described  on  page  132. 

REFERENCES. — Blair:  "The    Chemical    Analysis    of  Iron";    Lord    and 
Demorest:    "Metallurgical  Analysis." 


ALLOY  STEEL 

General. — This  method  covers  the  analysis  of  alloy  carbon 
steels,  i.e.,  those  containing,  in  addition  to  C,  Mn,  P,  Si,  and  S, 
one  or  more  of  the  following:  Cu,  Ni,  Cr,  V,  W,  Mo  and  Ti. 

In  those  cases  where  an  alternative  method  is  given,  the  latter 
is  to  be  used  only  when,  on  account  of  lack  of  chemicals  or  appa- 
ratus, the  first  method  cannot  be  employed. 

Sampling. — The  points  to  be  observed  in  sampling  alloy  steels 
for  analysis  are  the  same  as  those  mentioned  under  Carbon 
Steels  on  page  107. 

Total  Carbon. — Use  the  procedure  for  Carbon  Steels,  page 
108,  omitting  Note  1. 

Manganese  (Bismuthate  Method). — Dissolve  1  gram  of 
steel  in  60  cc.  of  HC1  (1:1).  When  solution  is  complete  add 
HNOs,  drop  by  drop,  to  oxidize  the  Fe.  Add  an  equal  volume  of 
EbO  and  boil  ten  minutes.  Filter  and  wash  any  WOs  with 
dilute  HC1  (1  :  7).  Replace  HC1  in  the  filtrate  with  HNO3  by 
evaporating  nearly  but  not  quite  to  dryness,  removing  the  last 
traces  with  AgNO3.  Then  add  75  cc.  of  HNO3  (1  :  3).  Cool 
and  proceed  according  to  the  Bismuthate  method  for  Manganese 
in  Carbon  Steel,  page  110,  titrating  with  standard  sodium  arsenite 
solution  as  there  described. 

Manganese  (Alternative  Method). — In  case  the  Cr  content 
of  the  steel  is  over  2%,  proceed  as  follows :  Dissolve  1  gram  of  steel 
in  60  cc.  of  HC1  (1:1).  Proceed  as  in  the  bismuthate  method  just 
described  until  the  last  traces  of  chlorides  have  been  replaced  by 
HNOs  by  evaporation.  Add  100  cc.  of  colorless  cone.  HNOa, 
set  on  the  hot  plate  and  heat  to  incipient  boiling.  Then  drop  in 
powdered  NaClOa  or  KClOa,  a  little  at  a  time,  adding  each  portion 


ANALYSIS  OF  METALS  117 

when  the  effervescence  produced  by  the  preceding  portion  has 
ceased.  By  the  time  2-2.5  grams  have  been  added  the  Mn02 
will  have  separated  as  a  fine  brown  powder.  Add  0.5  gram  more 
of  chlorate  and  boil  gently  ten  minutes.  If  any  SiC>2  is  present 
in  the  solution  after  three  or  four  minutes'  boiling,  add  a  few 
drops  of  pure  HF.  Then  add  1  gram  more  of  the  chlorate  and  25 
cc.  of  cone.  HNOs  and  boil  ten  minutes  longer.  Remove  from  the 
plate  and  cool  by  setting  the  beaker  in  water.  When  the  MnC>2 
has  settled,  filter  without  dilution  through  a  Gooch  crucible  with 
a  removable  bottom  and  asbestos  mat.  Finally  transfer  the 
MnC>2  to  the  filter  and  wash  the  beaker  and  filter  mat  with  color- 
less *  cone.  HNOa  3  or  4  times,  or  until  the  filtrate  is  colorless. 
This  can  be  done  without  using  more  than  15—20  cc.,  by  adding 
only  a  little  each  time  and  letting  each  portion  run  through  before 
adding  the  next.  Finally  wash  with  a  little  cold  water. 

After  washing  the  Mn(>2  with  cold  water  till  free  from  acid 
(letting  each  successive  portion  of  water  run  entirely  through  before 
adding  the  next,  so  as  not  to  use  in  all  more  than  20  cc.),  wash  the 
asbestos  and  precipitate  back  into  the  beaker,  which  always  has 
some  MnC>2  adhering  to  it. 

To  the  asbestos  and  MnC>2  in  the  beaker  add  standard  ferrous 
ammonium  sulfate  solution  (see  note)  from  a  burette,  5  cc.  at  a 
time,  until  after  stirring  and  warming  the  MnC>2  is  completely 
dissolved.  Break  up  with  a  glass  rod  all  lumps  of  asbestos  and 
precipitate.  Add  a  little  water  and  run  in  standard  KMn04 
solution  (see  note)  till  the  pink  color  remains  permanent  for 
two  or  three  minutes.  Read  the  burette  and  deduct  the  amount 
of  KMn04  from  its  equivalent  of  ferrous  ammonium  sulfate  solu- 
tion. The  difference  is  the  amount  of  standard  KMnOi  solution 
equivalent  to  the  Mn  present  in  the  precipitate.  Multiply  this 
difference  by  the  Mn  factor  of  the  KMnC>4  solution  and  divide  by 
the  weight  of  sample  taken.  This  result  multiplied  by  100  gives 
the  per  cent  of  Mn  in  the  sample. 

NOTE. — The  standard  ferrous  ammonium  sulfate  and  standard  KMnO4 
solution,  described  under  determination  of  Manganese  in  the  method  for 
Carbon  Steels  (page  111),  should  be  used  for  this  titration.  The  Mn  factor 

*  If  the  HNOs  is  colored  by  lower  oxides  of  N  (from  standing  and  the  action 
of  light),  it  can  be  purified  by  blowing  a  strong  current  of  air  through  until 
it  becomes  colorless. 


118  TECHNICAL  METHODS  OF  ANALYSIS 

is  not  the  same,  however,  as  when  the  bismuthate  method  is  used.     In  the 
bismuthate  method  the  following  reaction  takes  place: 


In  the  above  reaction  1  Mn  is  equivalent  to  5  Fe  and  the  Mn  factor  may  be 
calculated  from  the  Fe  factor  of  the  KMnO4  by  the  following  equation  : 

Mn  factor  =  Fe  factor  X  ^7—7. 
279  .  20 

=  Fe  f  actor  X  0.1967. 

When  the  MnO2  is  titrated  in  the  method  above  described,  however,  the 
following  reaction  takes  place  : 


In  this  reaction  1  Mn  is  equivalent  to  2  Fe  and  the  Mn  factor  may  be  cal 
culated  from  the  Fe  factor  of  the  KMnO4  by  the  following  equation: 

54  93 
Mn  factor  =  Fe  factor  X 


111.68 
=  Fe  factor XO. 4919. 

Phosphorus. — Dissolve  2-5  grams  of  steel  in  HNOs  (1  :  3)  in  a 
porcelain  dish,  evaporate  to  dryness  and  ignite  to  dull  red;  cool, 
dissolve  in  HC1  (1:1),  filter  and  convert  to  nitrate  by  evaporating 
nearly  to  dryness  with  HNOs  several  times.  Proceed  as  under 
"  Phosphorus  "  in  Carbon  Steel,  page  112. 

Silicon. — In  alloy  steels  containing  no  tungsten  determine  Si 
as  in  Carbon  Steels,  page  114. 

NOTES. — (1)  Silicious  residues  are  likely  to  be  contaminated  with  Ti  and 
Al  and  should  be  evaporated  with  HF  and  H2SO4. 

(2)  When  W  is  present,  the  WO3  and  SiO2  are  weighed  together  and  sep- 
arated as  described  later  under  Tungsten  (page  126). 

Sulfur. — Dissolve  5  grams  of  steel  in  50  cc.  of  cone.  HC1  and 
50  cc.  of  cone.  HNOs.  Evaporate  to  about  50  cc.  and  cautiously 
add  2  grams  of  Na2COs.  Transfer  the  solution  to  a  5-inch  por- 
celain dish  and  evaporate  to  dryness.  Dissolve  the  residue  in 
100  cc.  of  HC1  and  evaporate  to  10  cc.,  then  add  100  cc.  of  H^O 
and  10  cc.  of  HC1.  Filter,  heat  to  boiling,  and  precipitate  the 
SOs  with  10  cc.  of  a  hot  saturated  solution  of  BaCl2,  added  drop 
by  drop,  and  let  stand  overnight.  Filter  while  hot,  wash  with  a 
little  very  dilute  HC1  and  finally  with  cold  water.  Dry,  ignite 


ANALYSIS  OF  METALS  119 

and  weigh  as  BaS04.  If  this  ignited  precipitate  is  reddish  in  color, 
it  shows  that  Y^Os  has  been  carried  down  with  the  BaSO4.  In 
this  case  fuse  with  Na2COs,  dissolve  in  water,  filter,  acidulate  the 
filtrate  with  HC1,  boil  and  proceed  as  before.  Calculate  the  BaSC>4 
toS. 

CALCULATION.— BaSO4  X  0.1373  =  S. 

Copper. — Dissolve  5  grams  of  sample  in  a  mixture  of  150  cc.  of 
water  and  12  cc.  of  cone.  H2SO4.  Dilute  to  about  500  cc.  with  hot 
water,  heat  to  boiling  and  add  3  grams  of  sodium  thiosulfate  dis- 
solved in  10  cc.  of  hot  water.  Boil  a  few  minutes,  let  the  precip- 
itate settle,  filter  and  wash  with  hot  water.  Dry  the  precipitate 
(which  besides  the  CuS  may  contain  graphite,  silica,  etc.),  transfer 
to  a  small  beaker,  burn  the  filter  and  add  the  ash  to  the  main 
portion.  Digest  the  whole  with  aqua  regia,  dilute  with  hot  water, 
filter,  wash,  add  a  few  drops  of  H^SCU,  evaporate  to  fumes  of  SOa, 
cool,  dissolve  in  water,  add  15  cc.  of  cone.  HNOs,  dilute  to  about 
250  cc.  and  determine  the  Cu  by  electrolysis.  (See  page  145.) 

NOTES. — (1)  In  the  case  of  a  steel  insoluble  in  acid  or  containing  tungsten, 
treat  as  described  for  Manganese  (Bismuthate  method)  and  filter  off  the  WO3. 
To  this  filtrate  add  12  cc.  of  cone.  H^SCX,  evaporate  to  fumes  of  SOs,  dilute  to 
500  cc.  with  hot  water  and  proceed  as  described  above. 

(2)  Instead  of  determining  the  Cu  by  electrolysis,  it  may  be  determined  as 
CuO.  Dilute  the  sulfate  solution,  obtained  by  any  of  the  methods  men- 
tioned above,  with  water  to  about  50  cc.,  add  an  excess  of  NH4OH,  filter, 
wash  with  ammoniacal  water,  and  pass  H^S  through  the  cold  solution.  Filter, 
and  wash  with  H2S  water.  Dissolve  the  sulfide  in  aqua  regia  in  a  small  por- 
celain dish,  evaporate  nearly  to  dryness,  dilute  with  hot  water,  heat  to  boiling 
and  add  a  slight  excess  of  a  dilute  solution  of  NaOH  or  KOH.  Filter  on  a 
small  ashless  filter,  wash  with  hot  water,  dry,  transfer  the  precipitate  to  a 
platinum  crucible;  burn  the  filter  and  add  its  ash  to  the  precipitate;  moisten 
the  whole  with  HNO3,  and  heat,  very  gently  at  first,  increasing  the  heat 
slowly  to  redness.  Cool,  and  weigh  as  CuO.  Calculate  to  Cu. 

CALCULATION. — CuO  X0.7989  =  Cu. 

Nickel. — Dissolve  1  gram  of  steel  drillings  in  a  150  cc.  beaker 
with  20  cc.  of  HC1  (1  :  1).  When  action  ceases,  add  10  cc.  of 
HN03  (1:1).  Boil  until  red  fumes  have  been  driven  off,  add  100 
cc.  of  citric  acid  solution,  dilute  to  300  cc.,  and  add  with  a  pipette 
exactly  5  cc.  of  standard  AgNOs  solution.  Now  add  just  suf- 
ficient NILtOH  to  destroy  the  cloudiness,  then  2  cc.  of  KI  solu- 
tion, and  titrate  with  standard  KCN  solution  to  the  disappear- 
ance of  turbidity.  The  end  point  is  easy  for  an  experienced  operator 


120  TECHNICAL  METHODS  OF  ANALYSIS 

to  detect,  and  is  not  reached  as  long  as  a  drop,  when  striking  the 
solution,  produces  a  spot  clearer  than  the  liquid  around  it.  As 
soon  as  the  end  point  is  reached  all  turbidity  will  have  disappeared. 

The  cyanide  first  reacts  with  the  nickel,  then  attacks  the  iodide. 
If  it  is  thought  that  the  end  point  is  passed,  add  a  measured 
amount  of  AgNOs  until  a  turbidity  just  appears.  It  is  best  to  have 
another  beaker  containing  a  solution  to  be  titrated,  and  to  which 
no  AgNOs  has  been  added,  placed  beside  the  one  being  titrated  so 
as  to  have  a  clear  solution  of  the  same  color  to  compare  with. 
If  the  citric  acid  was  dirty,  the  solutions  will  be  cloudy  and  should 
be  filtered  before  AgNO3  is  added. 

SOLUTIONS. — (1)  Standard  Silver  Nitrate:  Dissolve  2.885  grams 
of  AgNOs  in  water  and  dilute  to  X  liter. 

(2)  Potassium  Iodide:   Dissolve  50  grams  of  KI  in  250  cc.  of 
water. 

(3)  Citric  Acid  Solution: 

380  grams  c.  P.  (NH4)2SO4; 
270  cc.  cone.  NH4OH; 
1430  cc.  H2O; 
240  grams  c.  p.  citric  acid. 

NOTE. — In  case  (NH4)2SO4  is  not  available  the  solution  may  be  made 
as  follows : 

(a)  Pour  166  cc.  of  cone.  H2SO4  into  250  cc.  of  H2O. 

(6)  Pour  712  cc.  of  cone.  NH4OH  into  880  cc.  of  H2O. 

Then  pour  (a)  into  (b)  very  carefully,  as  considerable  heat  is  produced; 
and  finally  dissolve  240  grams  of  citric  acid  in  the  mixture. 

(4)  Standard  Cyanide:  Dissolve  8.850  grams  of  pure  KCN  (or 
9.030  grams  of  98%  KCN)  and  10  grams  of  KOH  in  distilled 
H20  and  dilute  to  2000  cc. 

STANDARDIZATION. — The  KCN  solution  is  most  conveniently 
standardized  against  a  U.  S.  Bureau  of  Standards  3.50%  nickel 
steel,  the  same  procedure  being  followed  as  above,  each  cc.  of  the 
above  solution  being  equivalent  to  approximately  0.10%  nickel. 
An  additional  titration  must  be  made  in  order  to  obtain  the  relation 
between  the  AgNOs  and  the  KCN  solution.  This  is  accomplished 
in  the  solution  after  titration  for  standardization  by  adding 
exactly  10  cc.  of  standard  AgNOs  to  the  solution  and  running  in 
standard  KCN  to  the  disappearance  of  turbidity.  One-half  of 
the  amount  of  KCN  here  required  is  to  be  subtracted  from  the 


ANALYSIS  OF  METALS  121 

amount  used  in  each  determination.  Example:  Suppose  that 
10  cc.  of  AgNOs  required  5.2  cc.  of  KCN  to  destroy  the  turbidity. 
Suppose  further  that  it  took  5.6  cc.  of  KCN  in  the  actual  deter- 
mination. Then  5.6 — 2.6*  =  3.0  cc.  KCN  actually  required  by  the 
sample  to  destroy  turbidity.  Hence 

(3.0  cc.XNi  Factor)  v 

—  X100=  per  cent  Ni. 
(wt.  of  sample) 

Assuming  the  standard  steel  contains  exactly  3.50%  Ni,  then 

0.0350 


Ni  f actor  = 


(cc.  KCN  required) — (cc.  KCN  equiv.  to  5  cc.  AgNOs) 


NOTES. — (1)  The  presence  of  sulfates  is  necessary  to  obtain  a  sharp  end 
reaction.  Agl  is  soluble  in  a  large  excess  of  NH4OH,  so  care  should  be  taken 
to  have  the  solution  only  slightly  alkaline  with  NH4OH.  But  it  must  be 
alkaline. 

(2)  If  the  titrated  solutions  are  allowed  to  remain  in  open  beakers  for 
some  time  a  white  film  forms  on  the  surface,  but  no  account  is  to  be  taken  of  it. 

3.  When  2%  or  more  Cr  is  present,  proceed  exactly  as  described  above 
except  to  add  200  cc.  of  the  citric  acid  solution  instead  of  100  cc. 

(4)  The  AgNO3  solution  used  should  not  be  stronger  than  that  indicated 
above,  for  when  a  strong  silver  solution  is  used,  the  Agl,  instead  of  forming  a 
turbid  solution,  settles  out  as  a  curdy  precipitate,  which  does  not  readily  react 
with  the  cyanide. 

(5)  Such  elements  as  V,  Cr,  W,  Mo  or  Mn  do  not  interfere,  even  when 
present  in  large  amounts  in  the  sample.  Copper,  however,  is  titrated  with 
KCN,  but  is  usually  present  in  negligible  quantities.  If  its  presence  is  sus- 
pected, nickel  should  be  determined  by  the  dimethylglyoxime  method  (below). 

Nickel  (Alternative  Method). — Dissolve  1  gram  of  the  sample 
in  25  cc.  of  HC1  (1:1).  When  solution  is  complete,  add  HN03, 
drop  by  drop,  to  oxidize  Fe.  Add  an  equal  volume  of  water  and 
boil  ten  minutes.  Filter  into  a  600  cc.  beaker  and  wash  with  dil. 
HC1.  Boil,  and  add  10  grams  of  citric  acid  dissolved  in  50  cc.  of 
water.  Dilute  to  approximately  300  cc.,  render  slightly  alkaline 
with  NttiOH,  then  add  a  slight  excess  of  acetic  acid  and  heat  to 
boiling.  Now  add  about  20  cc.  of  dimethylglyoxime  solution,  or 
5  times  as  much  dimethylglyoxime  as  there  is  Ni  present.  Then 
add  NEUOH  until  the  solution  smells  slightly  of  NHa  or  reacts 
alkaline.  While  still  hot,  filter  on  a  weighed  Gooch  crucible, 
*  One-half  of  5.2  cc. 


122  TECHNICAL  METHODS  OF  ANALYSIS 

wash  well,  dry  at  110-120°  C.  for  forty-five  minutes  and  weigh. 
Calculate  to  Ni. 

CALCULATION. — Nickel  glyoximeX  0.2031  =  Ni. 

Chromium. — Dissolve  1  gram  of  steel  in  20  cc.  of  H^SCX  (1  :  3). 
When  solution  is  complete,  add  HNOs  drop  by  drop,  until  Fe  is 
oxidized.  (5  cc.  of  HNOs  (1  •'  3)  is  generally  sufficient.)  Boil  to 
remove  nitrous  fumes  and  dilute  to  150  cc.  with  hot  water.  Add 
to  the  boiling  solution  (a  pipette  is  convenient)  a  few  drops  at  a 
time  of  strong  KMnO4  solution,  boiling  between  each  addition, 
until  a  permanent  precipitate  of  Mn02  is  produced  which  does  not 
disappear  after  twenty  minutes'  boiling.  An  excess  over  the 
amount  necessary  to  do  this  should  be  avoided  as  it  will  render 
reduction  of  excess  KMnO4  to  MnC>2  very  difficult  and  will  neces- 
sitate prolonged  boiling.  Remove  from  the  heat  and  let  settle. 
If  reduction  of  excess  KMnC>4  to  MnO2  is  complete,  the  precipitate 
will  settle  quickly  leaving  a  clear  yellow  supernatant  liquid.  If 
reduction  is  not  complete,  the  precipitate  will  not  settle  quickly 
and  will  leave  a  pink  or  reddish  supernatant  liquid  and  must  be 
boiled  again.  Filter  the  cold  solution,  preferably  into  a  500  cc. 
Erlenmeyer  flask;  add  5  cc.  of  syrupy  HsPCX,  and  titrate,  adding 
a  known  excess  of  ferrous  ammonium  sulfate,  and  determining  the 
excess  with  standard  KMnC>4.  Subtract  the  KMnO4  required 
for  the  excess  titration  from  the  ferrous  ammonium  sulfate  orig- 
inally added  (in  terms  of  the  KMnO4)  and  calculate  the  difference 
to  Cr. 

The  HaPCU  decolorizes  ferric  salts,  giving  a  better  end  point, 
and  should  also  be  added  to  the  Fe(NH4)2(S04)2  solution  when 
obtaining  its  relation  to  the  KMnC>4  solution. 

SOLUTIONS. — (1)  Ferrous  Ammonium  Sulfate:  Dissolve  50 
grams  of  Fe(NH4)2  (864)2 -6H2O  in  1900  cc.  of  distilled  water  and 
add  100  cc.  of  cone.  H2SC>4. 

(2)  Permanganate:  Dissolve  1.58  grams  of  KMnO*  in  water 
and  dilute  to  1  liter. 

STANDARDIZATION. — The  Cr  factor  of  the  KMnCU  solution  is  ob- 
tained by  standardizing  against  0.7  gram  of  pure  Fe(NH4)2(SO4)2- 
6H2O  dissolved  in  15  cc.  of  cone.  H2SO4+150  cc.  of  H2O  to  ob- 
tain the  Fe  factor  and  calculating  from  this  the  Cr  factor  (also 
the  vanadium  factor  if  desired). 


ANALYSIS  OF  METALS  123 

CALCULATION. — Since  0.7  gram  of  Fe(NH4)2 (864)2  -GH^O  is 
equivalent  to  exactly  0.1  gram  of  Fe,  therefore  the  amount  of 

Fe  equivalent  to  1  cc.  of  the  KMnCU  =  —  — . 

cc.  KMnO4  used 

Since  1  Cr  is  equivalent  to  3  Fe  in  this  reaction,  we  have : 

52  0 
Cr  f actor  =  Fe  f actor  X — JT-T 

=  Fef actor  X  0.3 104. 

Vanadium  (Qualitative  Test). — Dissolve  0.5  gram  of  sample  in 
10  cc.  of  H2S04  (1  :  3),  heating  until  action  ceases.  Add  5  cc.  of 
cone.  HNOs  and  boil  until  no  more  red  fumes  are  evolved.  If  tung- 
sten is  present,  filter.  Pour  half  of  the  solution  into  each  of  two 
6-inch  test  tubes.  Then  add  to  one  tube  5  cc.  of  water  and  to  the 
other  5  cc.  of  3%  HfoCfe  solution.  If  V  is  present,  the  tube  to 
which  the  peroxide  was  added  will  be  distinctly  redder  than  the 
other,  even  if  there  be  only  a  few*  hundredths  of  a  per  cent  of  V 
in  the  sample.  If  Ti,  but  no  V,  is  present,  the  color  will  be  a 
clear  yellow.  If  a  red  color  is  produced,  V  is  present  and  pos- 
sibly Ti  also.  Add  0.05  N  FeSC>4  solution,  1  cc.  at  a  time,  shaking 
after  each  addition,  until  the  red  color  gradually  fades.  If  Ti 
is  present,  the  red  will  change  to  a  clear  yellow.  If  none  is  present, 
the  red  will  gradually  fade  out  without  changing  to  yellow. 

Vanadium  (Quantitative). — Dissolve  5  grams  of  drillings  in 
30  cc.  of  dil.  HC1  (1  :  1)  in  a  small  covered  beaker.  When  dis- 
solved, add  a  few  drops  of  HF,  warm,  and  add  gradually  1  or  2  cc. 
of  HNO3  to  oxidize  the  Fe.  Evaporate  to  about  10  cc.  Cool  and 
pour  into  a  150  cc.  separatory  funnel  with  a  very  short  stem. 
Wash  out  the  beaker  with  warm  HC1  (1:1)  transferring  all  the 
solution  to  the  funnel.  To  keep  the  volume  small,  use  successive 
small  portions  of  5-6  cc.  of  acid  in  washing.  The  total  volume  of 
solution  in  the  funnel  should  not  exceed  40  cc.  Now  cool  the 
funnel  and  contents  and  cautiously  add  45-50  cc.  of  ether,  pre- 
viously saturated  with  HC1.  Stopper  and  shake  vigorously  for 
five  minutes,  keeping  cool  by  holding  under  running  water.  Set 
the  funnel  in  a  rack  and  let  stand  until  the  ether  separates  and  the 
line  between  the  two  layers  is  sharp.  Then  remove  the  stopper 


124  TECHNICAL  METHODS  OF  ANALYSIS 

carefully  and  draw  off  the  aqueous  solution  down  to  the  stop-cock, 
being  careful  to  empty  the  stem.  Add  5-6  cc.  of  HC1  (1  :  1)  to 
the  ether  in  the  funnel  and  shake  again.  Let  separate  as  before, 
and  draw  off  the  acid,  adding  this  to  the  first  extract.  It  is  desir- 
able to  use  as  little  acid  as  possible  in  washing,  as  it  takes  up  some 
Fe  from  the  ether  and  increases  that  to  be  subsequently  removed 
from  the  aqueous  solution. 

During  the  whole  operation  the  ether  and  the  funnel  should 
feel  cool  to  the  hand;  if  allowed  to  become  too  warm,  vapor  pres- 
sure may  blow  the  stopper  out.  The  aqueous  solution  contains 
some  dissolved  ether,  a  little  Feds  (which  should  not  exceed  2% 
of  that  in  the  original  solution)  and  the  whole  of  the  chlorides  of 
V,  Ni,  Co,  Mn,  Al,  and  Cu.  Evaporate  this  solution  to  dryness 
several  times  with  a  large  excess  of  HC1  to  reduce  vanadic  acid  to 
divanadyl  chloride,  according  to  the  equation: 

V2O5+6HC1  =  2VOC12+3H2O+C12. 

Add  5  cc.  of  cone.  H2S04  and  evaporate  until  all  HC1  is  expelled 
and  fumes  of  80s  appear.  By  this  operation  divanadyl  sulfate 
is  formed: 

2VOC12+2H2S04==V202(S04)2+4HC1. 

Let  cool  and  dilute  to  200-300  cc.  Warm  to  about  60°  C.  and 
titrate  with  standard  KMnC>4  solution.  The  reaction  is: 

5V2O2(S04)2+2KMn04+8H2S04 

=  5V2O2(S04)3+K2S04+2MnS04+8H20. 

Comparing  this  with  the  reaction  for  titrating  ferrous  iron : 
10FeS04+2KMn04+8H2SO4 

=  5Fe2($04)3+K2S04+2MnS04+8H2O 
we  have  10V  :  510  =  lOFe  :  558 

or,  V  =  0.9133  Fe. 

Hence,  the  value  of  the  permanganate  solution  in  terms  of  Fe, 
multiplied  by  0.9133,  gives  its  value  in  terms  of  V. 

NOTES. — (1)  Small  amounts  of  ferric  salts  do  not  interfere  with  the  reac- 
tion, but  when  Cr  is  present  to  the  extent  of  2%  or  over,  the  color  of  the 


ANALYSIS  OF  METALS  125 

chrome  salt  masks  the  end  reaction.  The  color  of  the  divanadyl  sulfate  is 
pale  blue,  while  that  of  the  chromium  sulfate  is  green.  It  is,  therefore,  impos- 
sible to  tell  from  the  color  of  the  solution  under  the  conditions  whether  the 
sample  contains  V  or  not,  the  discoloration  of  the  permanganate  solution 
being  the  only  indication  of  its  presence. 

(2)  Run  a  blank  on  the  reagents  along  with  the  sample  and  deduct  from  the 
titration  before  calculating  to  V. 

Chromium  and  Vanadium. — Dissolve  1  gram  of  steel  in  50  cc. 
of  water  and  10  cc.  of  cone.  H^SO*  in  a  500  cc.  beaker  and  proceed 
as  described  previously  under  Chromium  until  the  solution  is 
ready  to  titrate.  Then  add  a  standard  ferrous  ammonium  sul- 
fate solution  until  the  solution  loses  all  brown  tints  and  assumes  a 
practically  colorless  shade  in  plain  vanadium  steels  or  a  green  color 
in  chrome  steels.  Then  add  a  few  more  cc.  to  make  sure  of  an 
excess.  Now  add  standard  KMnCX  solution,  slowly  and  with 
vigorous  agitation  of  the  solution,  until  a  very  faint  pink  is  ob- 
tained that  persists  after  thirty  seconds'  stirring.  Should  even 
as  much  as  5  or  6%  of  Cr  be  present,  a  practiced  operator  can 
easily  detect  the  pink  tints  through  the  chrome  green.  If  it  is 
desired  to  know  the  chromium  content,  the  amount  of  ferrous 
ammonium  sulfate  and  KMnCX  solutions  used  should  be  recorded 
and  the  Cr  content  calculated  as  described  previously  under  this 
element. 

Next,  just  destroy  the  pink  tinge  with  ferrous  ammonium  sul- 
fate solution.  The  solution  is  now  ready  for  the  vanadium  titra- 
tion. Add  2  cc.  of  a  2%  solution  of  potassium  ferricyanide 
(always  use  the  same  amount)  and  drop  in  slowly,  and  with  stirring, 
standard  ferrous  ammonium  sulfate  until  a  drop  produces  a  green 
color  free  from  yellow  tints.  If  much  Cr  is  present,  add  ferrous 
ammonium  sulfate  until  the  green  chromium  color  begins  to  darken. 
It  is  well  to  add  from  time  to  time  during  the  titration  a  drop  of 
the  indicator  and  note  if  a  green  coloration  is  produced  at  the 
point  where  the  drop  mixes  with  the  solution.  The  Fe  value  of 
the  ferrous  ammonium  sulfate  multiplied  by  0.9133  gives  the 
amount  of  V  present. 

A  "  blank  "  must  be  run  on  a  steel  free  from  V  but  otherwise 
of  similar  composition.  Also,  it  is  best  to  run  at  the  same  time  a 
V  determination  on  a  steel  containing  a  known  amount  of  V. 

.  NOTES. — (1)  The  presence  of  Cr  increases  the  blank.     If  Cu  is  present,  it 
will  precipitate  out  when  ferricyanide  is  added.     In  such  case,  add  ferri- 


126  TECHNICAL  METHODS  OF  ANALYSIS 

cyanide  before  the  MnO2  is  filtered  off,  and  filter  off  the  copper  ferricyanide 
with  the  MnO2.  If  a  further  precipitate  is  produced  when  ferricyanide  is  added 
for  titration,  run  another  determination  using  double  the  amount  of  ferri- 
cyanide to  precipitate  the  Cu.  Nickel,  if  present,  will  also  slowly  precipitate 
with  ferricyanide.  Mo  does  not  interfere.  If  the  sample  is  a  W  steel,  when 
it  is  dissolved  it  should  be  digested  until  the  precipitated  WO3  is  a  bright  yellow. 
Then  enough  permanganate  should  be  added  to  cause  the  precipitate  to  be 
colored  chocolate  by  the  MnO2  formed. 

(2)  It  is  absolutely  essential  in  V  and  Cr  titrations,  when  coming  back 
with  permanganate,  to  add  the  latter  until  3  drops  give  a  faint  pink  which 
remains  visible  after  thirty  seconds'  stirring.  The  ferrous  ammonium  sul- 
fate  should  be  added  until  3  drops  produce  a  distinct  darkening  of  the  green 
but  not  a  blue.  A  better  way  for  an  analyst  unfamiliar  with  the  reaction  is 
to  add  an  excess  of  permanganate  and  titrate  the  excess  with  standard  arsenite. 

Tungsten. — Weigh  accurately  1  gram  of  drillings  into  a  250  cc. 
beaker,  add  10  cc.  of  aqua  regia  (75  cc.  of  cone.  HC1+25  cc.  of 
cone.  HNOs),  and,  after  violent  action  ceases,  evaporate  to  dryness. 
Dissolve  the  residue  by  boiling  with  20  cc.  of  HC1  (1  :  1)  and  a  few 
drops  of  HNOs.  Now  dilute  with  100  cc.  of  H^O  and  boil  until 
the  WOs  precipitate  is  bright  yellow.  Filter,  wash  well  with 
hot  HC1  (1:1)  but  no  water,  to  remove  all  Fe.  Ignite  in  a  plat- 
inum crucible  until  all  paper  is  burned  off,  but  do  not  heat  the  WOs 
hotter  than  a  dull  red.  Cool  in  a  desiccator  and  weigh. 

Add  3  drops  of  EbSCX  and  5  cc.  of  HF  and  evaporate  off  the 
acids  under  a  good  hood,  finally  driving  off  the  H^SCX  by  heating 
the  crucible  near  the  top.  This  evaporation  must  be  carried  out 
with  extreme  care  to  avoid  loss  by  spattering.  Heat  to  dull  red 
and  weigh.  The  loss  in  weight  is  Si02.  Calculate  to  Si. 

CALCULATION.— SiO2  X  0.4693  =  Si. 

The  residue  of  WOs  always  contains  some  Fe20s.  To  correct 
for  this,  fuse  it  with  5  grams  of  Na2COs  and  a  few  small  crystals 
of  NaNOs  until  all  WOs  is  dissolved.  Dissolve  the  cold  cake  with 
hot  water  and  filter  off  the  residue  of  Fe2Os.  Wash  well  with  hot 
water,  burn  off  the  paper  and  weigh  the  residue.  Subtract  the 
weight  so  obtained  from  the  weight  of  the  impure  WOs  after  the 
SiO2  was  driven  off.  The  difference  is  the  weight  of  the  pure  WOs. 
Calculate  to  tungsten. 

CALCULATION.— WO3  X  0.7931  =  W. 

NOTE. — If,  when  filtering  the  WO3,  some  of  the  precipitate  adheres  to  the 
sides  of  the  beaker,  wash  the  acid  out  of  the  beaker,  then  remove  with  a  few  cc. 
of  NH4OH,  rinsing  into  the  platinum  crucible  with  a  little  water.  Evaporate 
to  dryness  and  then  place  the  filter  paper  in  this  crucible  to  ignite. 


ANALYSIS  OF  METALS  127 

Molybdenum  (Qualitative  Test). — Dissolve  0.5  gram  of  drill- 
ings in  25  cc.  of  HC1  (1  :  1).  Add  2  grams  of  KC1O3  and  heat 
until  the  residue  is  bright  yellow,  if  W  is  present.  Filter  and  add 
to  the  filtrate  10  grams  of  KOH  dissolved  in  10  cc.  of  water.  Boil 
for  several  minutes.  Filter  and  pour  the  solution  into  a  large 
test-tube.  Add  HG1  until  crystals  of  KC1  begin  to  form,  then  add  a 
few  grains  of  granulated  tin  and  heat  just  to  boiling  but  no  more. 
Cool  and  add  0.5  gram  of  KCNS.  If  Mo  is  present,  a  red  color 
develops,  the  depth  of  color  depending  upon  the  amount  present. 

The  precipitation  with  KOH  is  to  separate  out  the  Fe,  which 
would  also  give  a  red  color  with  KCNS.  The  solution  must  not 
be  heated  too  long  with  the  tin  present,  otherwise  the  delicacy  of 
the  test  will  be  impaired.  The  test  will  indicate  the  presence  of 
as  little  as  0.2%  of  Mo  or  less. 

Molybdenum  (Quantitative). — Place  2  grams  of  drillings  in  a 
450  cc.  beaker  and  cover  with  50  cc.  of  cone.  HC1.  Heat  to 
boiling  and  add  cone.  HNOs,  a  few  drops  at  a  time.  Con- 
tinue to  heat  the  solution  and  add  HNOs,  a  few  drops  at  a  time, 
until  the  sample  is  in  solution  and  the  Fe  is  oxidized.  Very  little 
more  HNOa  should  be  added  than  necessary  to  oxidize  the  Fe. 
A  black  film  of  carbonaceous  matter  will  remain.  Evaporate  to 
the  beginning  of  pastiness,  add  50  cc.  of  hot  water  and  10  cc.  of 
HC1  and  boil  a  few  minutes.  The  WOs  separates,  if  present. 
Filter  and  wash  with  hot  water  acidulated  with  HC1.  To  the 
filtrate  add  a  solution  of  NaOH,  shaking  the  flask  well  during  the 
addition,  until  most  of  the  free  acid  is  neutralized,  but  not  until  a 
darkening  in  color  takes  place.  Transfer  the  solution  to  a  sep- 
aratory  funnel. 

Open  the  stop-cock  of  the  funnel  so  that  the  solution  runs  out 
in  drops,  and  let  the  drops  fall  into  a  500  cc.  graduated  flask  con- 
taining 150  cc.  of  a  6%  solution  of  NaOH  heated  nearly  to  boiling. 
Shake  the  flask  vigorously  while  the  stream  of  drops  is  running  in. 
This  is  important,  as  otherwise  some  Mo  will  be  carried  down  with 
the  Fe(OH)s.  Finally  wash  the  funnel.  The  Fe  and  most  of  the 
Cr  are  precipitated  as  hydroxides.  A  little  Cr  goes  into  the  fil- 
trate as  chromate. 

Fill  the  500  cc.  flask  up  to  the  mark,  mix  well  and  filter  through 
a  large  paper  into  a  250  cc.  graduated  flask,  rejecting  the  first 
few  cc.  of  filtrate.  Transfer  250  cc.  of  the  filtrate  to  a  500  cc. 


128  TECHNICAL  METHODS  OF  ANALYSIS 

beaker  and  add  HC1  until  the  solution  is  just  acid  to  methyl 
orange,  then  add  4  cc.  of  cone.  HC1  in  excess.  Add  a  few  drops  of 
sulfurous  acid  to  reduce  the  small  amount  of  CrOs  usually  present, 
and  boil.  Add  40  cc.  of  NH*  acetate,  made  by  adding  30%  acetic 
acid  to  cone.  NILiOH  until  the  latter  is  neutralized.  Now  add 
40  cc.  of  a  1%  Pb  acetate  solution,  stir  well,  filter  through  a  close 
filter  paper  and  wash  well  with  hot  water.  Ignite  in  a  porcelain 
crucible  and  weigh  as  lead  molybdate.  Calculate  to  Mo. 
CALCULATION.— PbMoO4  X  0.2614  =  Mo. 

NOTES. — (1)  When  the  sample  is  dissolved  and  oxidized  with  HNO3,  a 
little  molybdic  acid  may  precipitate,  and  would  appear  with  the  WO3  if  any 
were  present. 

(2)  The  treatment  with  NaOH  forms  Na2MoO4  which  is  soluble,  while  the 
Fe  separates  as  Fe(OH)3.     If  the  acid  solution  is  not  added  slowly  and  with 
vigorous  stirring  the  Fe(OH)3  will  carry  down  with  it  some  molybdic  acid. 
Ammonium  acetate  is  added  to  reduce  the  acidity,  according  to  the  disso- 
ciation theory. 

(3)  If  much  W  is  present,  the  WO3  should  be  dissolved  in  NaOH  solution, 
diluted  to  50  cc.,  HC1  added  until  the  solution  is  acid  and  then    20  cc.  in 
excess,  and  the  solution  evaporated  to  10  cc.,  diluted  to  50  cc.  and  boiled; 
the  WO3  filtered  off  and  the  filtrate  added  to  the  main  filtrate. 

Titanium  (Qualitative  Test). — See  Vanadium  (Qualitative). 

Titanium  (Quantitative). — Add  to  1  gram  of  sample  in  a  500 
cc.  flask  40  cc.  of  H2SO4  (1  :  3).  Heat  to  boiling  until  no  more 
action  takes  place.  Disregard  any  residue.  Dilute  to  250  cc. 
and  add  NHtOH  until  a  slight  precipitate  forms,  then  add  a  few 
grams  of  Na2S20s  and  a  few  drops  of  H^SC^,  or  enough  to  make  the 
solution  clear.  Heat  until  all  Fe  is  reduced,  as  shown  by  testing  a 
drop  with  KCNS;  then  add  a  solution  containing  25  cc.  of  water, 
15  cc.  of  cone.  NBLtOH,  and  10  grams  of  KCN.  Heat  to  boiling 
for  several  minutes.  Prepare  a  filter  by  shaking  two  9  cm.  filter 
papers  in  a  flask  with  water  until  well  macerated  and  then  pouring 
the  pulp  through  a  funnel  containing  a  platinum  cone.  Place  this 
funnel  in  a  suction  flask  and  pour  the  solution  through,  using 
suction.  The  solution  should  filter  quickly  to  prevent  oxidation  of 
Fe.  Wash  well  with  water. 

Burn  the  paper  and  contents  in  a  platinum  crucible  until  all 
paper  is  consumed;  then  add  4  grams  of  KHSO4,  which  has  been 
previously  fused  to  remove  water;  fuse,  and  maintain  at  bright 
red  heat  for  several  minutes.  Cool,  then  add  water  enough  to 


ANALYSIS  OF  METALS  129 

half  fill  the  crucible  and  5  cc.  of  H2S04,  and  heat  until  the  cake  is 
all  dissolved.  Cool,  transfer  to  a  Nessler  tube  or  other  color  com- 
paritor,  dilute  to  100  cc.  and  add  3  cc.  of  H202  (ordinary  3% 
solution).  If  Ti  is  present,  a  yellow  color  will  immediately  appear. 
To  the  other  tube  add  100  cc.  of  5%  H2S04,  3  cc.  of  H202  and 
standard  titanium  sulfate  solution  a  little  at  a  time,  shaking 
after  each  addition,  until  the  color  matches  the  color  of  the 
solution  of  the  sample.  The  Ti  in  the  sample  will  then  be  the 
same  as  the  amount  added  to  the  comparison  tube. 

NOTES. — (1)  H2O2  containing  acetanilide  or  any  other  preservative  should 
not  be  used.  The  pure  3%  H2O2  solution  is  satisfactory. 

(2)  Standard  Titanium  Solution:  Ignite  pure  TiO2  at  dull  red  heat  to  con- 
stant weight.  Weigh  0.5  gram  of  the  anhydrous  powder  in  a  platinum 
crucible  with  5  grams  of  pure  KHSC>4.  Melt  cautiously  and  keep  at  a  low  red 
heat  for  5-10  minutes  until  the  TiO2  all  dissolves  and  the  liquid  becomes 
clear.  Partially  cool  the  crucible  and  add  5  cc.  of  cone.  H2SO4,  then  heat 
again  till  the  mass  liquefies.  Cool,  and  put  the  crucible  and  contents  into 
200-300  cc.  of  water  containing  5%  of  H2SO4.  When  the  fusion  is  dis- 
solved, wash  and  remove  the  crucible.  The  TiO2  should  dissolve  to  a  clear 
solution.  If  any  residue  remains,  filter  it  out,  wash,  ignite  and  weigh,  and 
deduct  it  from  the  TiO2  taken,  using  the  difference  in  calculating  the  strength 
of  the  solution.  Finally,  dilute  the  solution  with  5%  H2S(>4  till  1  cc.  contains 
0.001  gram  of  titanium. 

TiO2X0.6005  =  Ti. 

REFERENCES. — Lord  and  Demorest:  "Metallurgical  Analysis,"  Fourth 
Edition;  Blair:  "Chemical  Analysis  of  Iron";  Johnson:  "  Chemical  Analysis 
of  Special  Steels." 

PIG  AND  CAST  IRON 

General. — This  method  applies  to  all  classes  and  grades  of  pig, 
charcoal  and  cast  irons.  Where  an  alternative  procedure  is  given, 
the  latter  is  to  be  used  only  when,  on  account  of  lack  of  chemicals 
or  apparatus,  the  first  method  cannot  be  employed. 

Sampling. — The  points  to  be  observed  in  sampling  iron  for 
analysis  are  as  follows: 

(1)  The  sample  should  preferably  be  drillings  taken  without 
the  application  of  water,  oil  or  other  lubricant,  and  should  be  free 
from  sand,  dirt  or  other  foreign  matter.  A  magnet  must  not  be 
used  in  separating  the  iron  from  foreign  matter  on  account  of  the 
danger  of  losing  graphitic  carbon  which  is  non-magnetic. 


130  TECHNICAL  METHODS  OF  ANALYSIS 

(2)  All  samples  should  be  ground  uniformly  in  a  hardened  steel 
mortar. 

(3)  Drillings  in  the  case  of  cast  iron  should  represent  the 
entire  cross  section  of  material  less  than  1  inch  thick.     On  material 
over  1  inch  thick,  the  sample  should  be  taken  midway  between 
the  surface  and  the  center. 

(4)  Drillings  in  the  case  of  pig  iron  should  be  taken  midway 
between  the  surface  and  the  center. 

Total  Carbon. — Determine  total  carbon  by  the  solution-com- 
bustion method.  For  the  general  arrangement  of  the  combustion 
apparatus,  see  page  108. 

Dissolve  1  gram  of  sample,  using  75  cc.  of  a  solution  of  copper 
potassium  chloride.  Stir  constantly  with  a  mechanical  stirrer 
until  the  sample  is  dissolved  (see  Note  1)  or  let  stand  overnight. 
(Complete  solution  is  shown  by  the  disappearance  of  all  Cu  from 
the  bottom  of  the  beaker.)  Filter  on  a  previously  ignited  asbestos 
mat  in  a  loose  bottom  Gooch  crucible.  Wash  5  times  with  HC1 
(1  :  10),  then  5  times  with  water.  Do  not  let  air  draw  through 
the  mat  and  residue  during  filtering  and  subsequent  washing. 
Transfer  the  mat  and  contents  to  the  combustion  boat,  being  care- 
ful not  to  lose  any  of  the  carbon,  and  dry  at  100°  C. 

Introduce  the  boat  with  the  residue  into  the  center  of  the  com- 
bustion tube,  which  is  maintained  at  850-900°  C.  for  this  deter- 
mination (also  that  of  graphitic  carbon).  Admit  oxygen  at  the 
approximate  rate  of  26  bubbles  per  ten  seconds,  or  250  cc.  every 
ten  minutes.  As  soon  as  the  carbon  begins  to  burn,  there  is  at 
first  a  rapid  evolution  of  gas,  which  quickly  ceases.  When  the 
oxidation  of  the  residue  is  completed,  the  oxygen  begins  to  flow 
at  normal  speed  again.  Allow  thirty  minutes  for  oxidation  of  the 
carbon  residue  and  sweeping  of  all  CO2  from  the  combustion  tube 
into  the  absorption  apparatus.  Weigh  the  CC>2  formed  and  cal- 
culate to  C. 

CALCULATION.— CO2  X  0.2728  =  C. 

Copper  Potassium  Chloride  Solution:  Dissolve  900  grams  of 
2KCl-CuCl2-2H2O  in  2700  cc.  of  water  and  add  215  cc.  of  cone. 
HC1.  Filter  the  solution  through  glass  wool  and  asbestos. 

NOTES. — (1)  We  have  found  the  rotating  electrode  a  very  convenient 
ptirrer  for  getting  the  sample  into  solution.  Of  course  no  current  should  be 
passed  when  it  is  used  for  this  purpose 


ANALYSIS  OF  METALS  131 

(2)  This  method  cannot  be  used  if  the  material  is  an  alloy  iron.     In  this 
case  a  portion  of  the  sample  passing  a  20-  but  not  a  30-mesh  sieve  must  be 
mixed  with  2  grams  of  litharge  and  the  carbon  determined  by  direct  com- 
bustion at  1000°  C.     A  "blank"  must  be  carefully  determined  upon  the 
litharge  at  the  same  temperature  before  using,  and  this  blank  deducted  from 
the  weight  of  CO2  found. 

(3)  See  also  notes  (2)  to  (6)  inclusive,  under  Total  Carbon  in  Carbon 
Steel,  page  109. 

Graphitic  Carbon. — Weigh  1  gram  of  sample  into  a  200  cc. 
beaker  and  add  60  cc.  of  HNO3  (1  :  3).  Heat  the  beaker  on  the 
steam  bath  until  the  iron  is  all  dissolved.  Filter  on  a  loose  bottom 
Gooch  crucible  through  asbestos  and  wash  with  water;  HC1 
(1  :  1);  H2O;  NHjOH  (1%);  H2O;  HC1  (1:1);  H2O;  and  H2O, 
in  the  order  indicated.  Transfer  the  asbestos  and  contents  to 
the  combustion  boat,  heat  until  dry  in  the  oven  at  100°  C.  and 
determine  carbon  in  the  regular  way. 

Combined  Carbon. — Combined  C  equals  total  C  minus  gra- 
phitic C. 

In  special  cases  the  combined  C  may  be  determined  colori- 
metrically  as  follows: 

Dissolve  0.2  gram  of  sample  in  6  cc.  of  HNOs  (1  :  3)  in  a  small 
test  tube,  filter,  washing  with  the  least  possible  amount  of  water, 
and  compare  the  color  with  a  standard  pig  iron  run  in  the  same 
manner.  The  standard  iron  must  not  vary  more  than  0.1%  in 
carbon  from  the  unknown. 

Manganese  (Bismuthate  Method). — Dissolve  1  gram  of  drill- 
ings in  25  cc.  of  HNOs  (1  :  3)  in  a  small  beaker.  When  dissolved, 
filter  into  a  200  cc.  Erlenmeyer  flask,  wash  with  30  cc.  of  HNO3 
(1  :  3),  cool  the  filtrate,  add  about  0.5  gram  of  Na  bismuthate, 
boil  until  the  pink  color  has  disappeared  and  dissolve  any  pre- 
cipitate of  MnO2  by  .adding  a  few  drops  of  a  saturated  solution  of 
FeSO4  or  of  sodium  thiosulfate;  then  heat  until  all  nitrous  fumes 
have  been  driven  off,  cool  to  60°  F.,  add  about  0.5  gram  of  Na 
bismuthate  and  shake  the  flask  vigorously  for  a  few  minutes. 
Add  50  cc.  of  3%  HNOs*  and  filter  the  solution  into  a  suction 
flask  through  an  extra-porous  alundum  thimble,  taking  care  not 
to  fill  the  thimble  so  full  that  any  of  the  solution  comes  in  contact 

*  This  acid  is  prepared  by  adding  60  cc.  of  cone.  HNO3  to  1940  cc.  of  H2O 
and  then  adding  3-4  grams  of  Na  bismuthate  and  shaking.  It  should  be 
allowed  to  stand  overnight  before  using. 


132  TECHNICAL  METHODS  OF  ANALYSIS 

with  the  rubber  connection.  Wash  with  50-100  cc.  of  the  same 
acid  and  finally  with  water.  From  here  proceed  as  directed  on 
page  111,  using  for  the  standardization  an  iron  of  known  man- 
ganese content  instead  of  a  steel. 

Phosphorus.  —  Dissolve  1  gram  of  the  sample  in  a  250  cc.  beaker 
with  100  cc.  of  HN03  (1  :  3).  Add  5  cc.  of  saturated  KMnO4  solu- 
tion and  boil  until  the  excess  KMnC>4  is  decomposed  and  the  solu- 
tion contains  precipitated  Mn02.  Add  a  few  crystals  of  tartaric 
acid  and  boil  until  the  solution  clears,  then  a  few  minutes  longer, 
to  drive  off  all  nitrous  fumes.  Filter  into  a  500  cc.  Erlenmeyer 
flask  and  wash  the  precipitate  thoroughly  with  hot  water.  Add 
15  cc.  of  cone.  NELtOH  and  proceed  as  described  under 
Phosphorus  in  Carbon  Steel  on  page  112. 

Silicon.  —  Weigh  1  gram  of  the  iron  into  a  12  cm.  casserole  or 
evaporating  dish  and  add  60  cc.  of  silicon  mixture  (see  Note  2). 
When  effervescence  ceases,  rinse  the  sides  of  the  dish  with  water 
and  cover  with  a  watch  glass.  Place  on  the  hot  plate  and  boil 
slowly  but  continuously  until  a  white  crust  of  FeSO4  forms  and 
SOs  fumes  appear.  Remove  the  dish  from  the  hot  plate  and  cool. 
Dilute  immediately  with  75  cc.  of  HC1  (1  :  3)  and  bring  to  a  boil; 
keep  at  the  boiling  point  until  the  solution  is  clear.  Filter  while 
hot  through  an  11  cm.  filter,  washing  with  hot  HC1  (1  :  1)  and 
hot  water  alternately  until  SiC>2  and  paper  are  free  from  iron. 
Then  wash  the  paper  free  from  acid.  Ignite  strongly  and  weigh 
as  SiC>2.  Calculate  to  Si. 

CALCULATION.—  SiO2  X  0.4693  =  Si. 

NOTES.  —  (1)  If  the  precipitate  is  red  from  undissolved  Fe,  volatilize  with 
HF.  Ignite  and  weigh  again.  The  loss  in  weight  is  SiO2.  Calculate  to  Si. 

(2)  Silicon  Mixture.—  To  1500  cc.  of  water  add  500  cc.  cone.  HNO3  and 
then  150  cc.  of  cone.  I^SCX  with  constant  stirring. 


Sulfur  (Evolution  Method).  —  Proceed  as  on  page  115. 

NOTE.  —  In  the  case  of  very  coarse  drillings  which  dissolve  slowly,  consid- 
erable acid  may  be  carried  over  and  neutralize  the  NH3  in  the  CdCl2  solu- 
tion. In  such  cases  care  must  be  taken  to  keep  the  solution  up  to  original 
strength  in  NH3.  If  such  samples  are  encountered,  it  is  preferable  to  use  the 
Elliott  Method  as  described  below. 

Sulfur  (Elliott  Evolution  Method).  —  Thoroughly  mix  5  grams 
of  the  sample  with  0.25  gram  of  pure,  finely  powdered  anhydrous 


ANALYSIS  OF  METALS  133 

potassium  ferrocyanide,  and  wrap  in  an  11  cm.  filter  paper.  Place 
in  a  small  porcelain  crucible,  cover  and  anneal  at  750-850°  C. 
for  twenty  minutes  in  a  closed  muffle.  Cool  slowly  outside  the 
muffle.  The  material  should  be  covered  practically  completely 
by  the  charred  paper,  if  the  temperature  has  not  been  above 
850°  C.  or  if  it  has  not  been  in  the  muffle  too  long.  After  cooling, 
crush  the  contents  of  the  crucible  slightly  in  a  glass  mortar  and 
finally  transfer  to  a  500  cc.  Florence  flask. 

Connect  the  evolution  flask  with  a  condensing  tube  (lX8-in. 
test  tube)  containing  about  2  inches  of  water  and  standing  in  a 
conical  beaker  filled  with  cold  water.  A  tube  from  this  dips  into 
a  second  test  tube  containing  60  cc.  of  CdCb  solution,  which  again 
is  connected  with  another  test  tube  containing  more 
(See  Fig.  7.) 


FIG.  7. — Apparatus  for  Sulfur  in  Iron.     (Elliott  Evolution  Method.) 

Add  50  cc.  of  cone.  HC1  to  the  evolution  flask  and  heat  until  the 
sample  is  in  solution  and  all  H^S  has  been  driven  over.  Discon- 
nect the  apparatus  and  wash  the  CdS  into  a  tumbler.  Add  3  cc. 
of  starch  solution  and  15  cc.  of  cone.  HC1  and  titrate  at  once  with 
standard  iodine  solution  to  the  appearance  of  a  permanent  blue. 

SOLUTIONS. — (a)  Cadmium  Chloride  Solution. — Dissolve  20 
grams  of  CdCU  in  water  with  the  aid  of  a  few  drops  of  HC1. 
Then  add  NHiOH  until  the  precipitate  completely  redissolves. 
Make  slightly  acid  with  acetic  acid  and  then  add  20  cc.  excess. 
Dilute  to  2  liters. 

(6)  Standard  Iodine  Solution. — The  same  as  used  in  the  pre- 
vious evolution  method  (page  115). 

(c)  Starch  Solution. — The  same  as  already  described  in  the 
previous  evolution  method  (see  page  12). 

STANDARDIZATION. — Standardize  exactly  as  described  under 
Sulfur  in  Carbon  Steel  (page  115). 


134  TECHNICAL  METHODS  OF  ANALYSIS 

NOTE. — Copper,  titanium  and  vanadium  are  sometimes  called  for  in  this 
class  of  material,  and  they  may  be  detected  and  quantitatively  determined 
as  described  in  Blair,  7th  edition,  pages  184-185. 

REFERENCES. — Blair:  "  Chemical  Analysis  of  Iron."  Lord  and  Demorest : 
"  Metallurgical  Analysis." 

TIN  IN  TIN  ORES 

General. — Tin  seldom  exists  in  nature  in  the  metallic  state. 
It  occurs  both  in  veins  and  in  alluvial  deposits.  Cassiterite 
or  tin-stone  is  its  most  important  ore.  This  is  a  tin  oxide  (SnO2) 
and  generally  occurs  in  alluvial  deposits.  The  color  of  the  oxide 
may  be  black,  brown,  reddish  yellow,  red  and  brownish  white. 
The  streak  is  white  to  brownish.  When  pure  the  ore  contains 
78.77%  Sn.  Its  sp.  gr.  is  6.8-7.1.  Another  ore  is  stannite 
(sp.  gr.  4.3^4.52),  a  compound  of  Sn,  S,  Fe,  Cu,  and  sometimes 
Zn. 

The  impurities  most  frequently  associated  with  the  oxide  are 
pyrite,  arsenopyrite,  wolframite  (tungstate  of  Fe  and  Mn), 
chalcopyrite,  titaniferous  iron,  columbite,  iron  oxide,  tourmaline, 
and  sometimes  blende  and  galena.  To  determine  whether  the 
mineral  is  SnC>2,  fuse  a  finely  ground  portion  in  a  porcelain  crucible 
with  3  or  4  times  its  weight  of  NaCN  and  dissolve  the  mass  in 
water.  A  tin  globule,  or  globules,  will  be  found  if  the  material 
is  SnC>2.  The  sample  may  also  be  mixed  with  Na2COs  and  char- 
coal and  fused  on  charcoal  in  a  reducing  flame. 

When  in  veins  the  gangue  generally  consists  of  granite,  slate, 
syenite,  quartz  or  feldspar,  and  often  carries  garnets  and  zircons. 
Fluorspar  is  also  frequently  present,  and  by  some  is  considered  a 
good  indicator  of  tin-stone. 

Portions  of  the  deposit  are  often  very  rich,  but  average  ore, 
whether  from  veins  or  placers,  carries  only  1-5%  SnO2-  On 
this  account  samples  can  very  rarely  be  assayed  by  fire,  or  even 
analyzed  in  the  wet  way  directly.  Owing  to  its  high  specific 
gravity,  however,  we  can  resort  to  washing  and  concentration, 
thus  separating  it  from  gangue  and  some  other  impurities. 
Wolframite,  unfortunately,  has  a  sp.  gr.  of  7.2-7.5,  slightly 
higher  than  SnO2.  This  necessitates  subsequent  purification  when 
this  mineral  is  present.  If  the  tin-stone  carries  much  iron  oxide, 
this  must  be  removed  with  acids,  otherwise  the  resulting  tin  will 


ANALYSIS  OF  METALS  135 

not  collect  in  a  button,  but  will  contain  Fe  and  be  a  porous  and 
magnetic  mass.     The  following  are  the  steps  in  the  assay: 

1.  Concentration. 

2.  Roasting  concentrates. 

3.  Panning  concentrates  and  boiling  in  aqua  regia. 

4.  Panning  concentrates  again. 

5.  Assaying  final  concentrates. 

If  the  concentrates  obtained  from  the  first  panning  are  very 
pure,  some  of  the  later  steps  may  be  omitted. 

Concentration. — Weigh  500-1000  grams  of  ore,  crushed  at  least 
as  fine  as  40-mesh  size.  If  crushed  too  fine,  the  SnC>2  will  slime 
badly,  but  it  must  be  fine  enough  to  liberate  SnC>2  from  the  gangue. 
Carefully  pan  the  ore  again  and  again  until  no  more  concentrates 
can  be  obtained.  This  is  done  by  placing  the  ore  in  a  shallow  pan, 
running  a  little  water  into  the  pan  and  shaking.  Then  carefully 
pour  off  the  lighter  constituents  of  ore  or  tailings,  allowing  the 
heavy  metallic  compounds  to  settle  to  the  bottom.  Do  not  pan 
too  closely;  if  a  little  gangue  is  left  with  the  concentrates  it  does 
no  harm.  Discard  the  waste  matter  or  tailings. 

Roasting. — Dry  the  concentrates  (consisting  of  SnO2,  pyrite, 
and  whatever  heavy  material  happens  to  be  in  the  ore,  together 
with  a  small  amount  of  gangue)  and  then  place  in  a  clay  or  iron 
roasting  dish.  Place  this  in  a  muffle,  the  bottom  of  which  is 
hardly  red,  and  heat  slowly.  When  the  odor  of  862  can  no  longer 
be  detected,  remove  the  dish,  cool,  and  stir  a  little  fine  charcoal 
into  the  ore.  This  reduces  sulfates,  arsenates  and  antimoniates 
to  lower  forms  and  enables  Sb  and  As  to  be  set  free,  and  is  espe- 
cially necessary  when  As  is  present.  Roast  again,  and  repeat 
until  a  dead  roast  is  obtained.  This  point  is  reached  when  no 
more  fumes  of  SO2  or  As2Os  are  given  off.  Everything  in  the 
concentrates  should  now  be  in  the  form  of  oxides.  They  can  now 
be  panned  to  remove  oxides  of  iron  and  silica  and  then  treated 
with  acid,  or  treated  with  acid  directly  and  then  panned. 

Treatment  with  Acid. — Boil  the  concentrates  in  aqua  regia, 
in  which  SnC>2  is  insoluble.  This  practically  removes  everything 
except  some  SiO2,  TiC>2  and  compounds  insoluble  in  aqua  regia. 
If  much  SiC>2  is  present,  pan  again.  In  some  cases  it  is  well  to 
grind  finely  the  tailings  from  this  concentration  and  pan  again. 


136  TECHNICAL  METHODS  OF  ANALYSIS 

Dry  the  total  concentrates,  weigh  and  grind  to  pass  an  80-mesh 
sieve. 

Assaying. — The  concentrates  are  now  ready  for  assaying, 
which  may  be  done  by  various  methods.  The  following  cyanide 
method  of  Levol  has  been  found  to  give  excellent  results.  On 
clean  ores  or  concentrates  it  is  very  accurate,  but  in  ores  con- 
taining much  foreign  matter,  the  assay  is  rendered  much  more 
difficult  and  the  time  of  the  fusion  must  be  increased. 

Mix  5-10  grams  of  concentrates  with  4  times  as  much  NaCN. 
(Poison!)  Have  a  good  layer  of  NaCN  in  the  bottom  of  the 
crucible,  next  put  in  the  mixture  of  concentrates  and  NaCN  and 
then  place  a  layer  of  NaCN  on  top.  Use  Battersea  A  or  Denver 
fire  clay  crucible  of  similar  size.  Heat  very  s  owly  at  first  in  a 
Fletcher  gas  muffle  furnace  and  just  fuse  to  reduce  SnO2  to  Sn 
and  then  keep  just  fused  for  twenty  to  thirty  minutes.  Increase 
the  temperature  ten  to  fifteen  minutes  longer,  remove  from  the 
fire,  tap  gently  and  transfer  to  some  place  where  the  fumes  will 
not  be  carried  into  the  laboratory. 

The  purer  the  SnO2,  the  shorter  is  the  necessary  period  of 
fusion.  With  some  ores  the  fusion  may  be  completed  in  ten 
minutes  with  good  results,  but  ordinarily  the  above  time  will  be 
required  for  a  satisfactory  fusion.  Never  let  the  fuson  boil, 
which  causes  low  results. 

Let  the  crucible  become  perfectly  cold,  being  careful  not  to  dis- 
turb during  cooling.  Break  the  crucible  and  free  the  button  from 
the  mass.  If  decomposition  of  the  ore  is  complete,  a  clean  bright 
tin  button  should  be  obtained.  If  fusion  is  incomplete,  some  ore 
will  still  remain  undecomposed  and  the  entire  fusion  must  be 
repeated.  Free  the  button  entirely  from  cyanide,  dry  and  weigh. 
Calculate  the  per  cent  of  total  metal  in  the  original  ore. 

On  very  high-grade  ores,  containing  50%  or  better  of  Sn,  it  is 
often  possible  to  fuse  the  ore  directly  with  NaCN,  omitting  con- 
centration, roasting  and  acid  treatment.  If  these  steps  are  omit- 
ted it  may  be  necessary,  in  order  to  obtain  a  clean  button,  to  add  a 
little  Na2COs  to  the  fusion  mixture  in  order  to  take  care  of  silica. 
A  trial  fusion  should  be  made  first,  however,  with  cyanide  alone 
and  then  if  a  satisfactory  button  is  not  obtained,  another  fusion 
should  be  made  by  adding  a  little  Na2COs. 

The  button  may  contain,  besides  metallic  Sn,  small  amounts  of 


ANALYSIS  OF  METALS  137 

Sb  and  other  metals.  In  order  to  obtain  the  true  tin  content  of  the 
ore  it  is  necessary  to  determine  the  amount  of  tin  in  the  button. 
This  may  be  done  by  the  volumetric  method  described  under 
Solder  on  page  155.  The  percentage  of  tin  obtained  should,  of 
course,  be  calculated  back  to  the  original  ore. 

ZINC  (SPELTER) 

General. — Spelter  ordinarily  used  for  brass  and  similar  alloys 
is  usually  classified,  according 'to  the  amounts  of  Pb  and  other 
impurities  present,  into  four  grades:  A,  "  High  Grade  ";  B,  "  Inter- 
mediate ";  C,  "  Brass  Special  ";  and  D,  "  Selected."  A  fifth  and 
still  lower  grade,  "  Prime  Western,"  is  principally  used  for  gal- 
vanizing. These  grades  are  covered  by  the  specifications  of  the 
American  Society  for  Testing  Materials  in  its  Triennial  Standards 
for  1918,  pages  437-438. 

The  methods  of  sampling  and  analysis  described  below  are 
those  generally  accepted  in  the  United  States  as  standard  in 
all  the  larger  laboratories  of  both  producers  and  consumers  of 
zinc  and  zinc  products.  The  methods  of  analysis  are  those 
originally  proposed  by  Elliott  and  Storer  and  Price.  Alternative 
methods  are  only  to  be  used  when  apparatus  or  chemicals  required 
in  the  preferred  method  are  not  available. 

Sampling. — Select  10  slabs  at  random  from  a  carload  and  saw 
each  slab  completely  across  from  the  middle  of  one  long  side  to 
the  middle  of  the  other  and  use  the  sawdust  for  analysis.  Or,  drill 
three  9  mm.  (f  inch)  holes  along  one  diagonal  of  each  slab,  boring 
completely  through  and  taking  care  to  make  fine  drillings.  The 
holes  should  be  drilled  as  nearly  as  possible  at  the  middle  and  half- 
way between  either  end  and  the  middle  of  such  diagonals.  Go 
over  the  drillings  or  sawings  with  a  powerful  magnet  to  take  out 
any  iron  which  may  have  come  from  the  drill  or  saw,  and  mix  the 
sample  thoroughly.  The  drill  or  saw  must  be  thoroughly  cleaned 
before  use,  and  no  lubricant  shall  be  used  in  either  drilling  or  saw- 
ing. 

Lead  (Electrolytic  Method).— Place  8.643  *  grams  of  sample  in 

*  An  empirical  factor  weight  8.643  is  used  instead  of  the  theoretical  one 
(8.662)  according  to  the  American  Society  for  Testing  Materials:  Triennial 
Standards,  1918  and  E.  F.  Smith's  "  Electro  Analysis,"  Fourth  Edition,  page 
102. 


138  TECHNICAL  METHODS  OF  ANALYSIS 

a  400  cc.  beaker  and  add  sufficient  water  to  cover.  Then  add 
gradually  and  cautiously  30  cc.  of  cone.  HNOs.  When  action  is 
complete,  boil  the  solution  for  a  few  minutes  to  expel  nitrous  fumes. 
Wash  the  watch  glass  and  the  sides  of  the  beaker  and  transfer  the 
solution  to  a  250  cc.  beaker.  Dilute  to  200  cc.  and  electrolyze, 
using  a  rotating  platinum  cathode  and  a  stationary  platinum  gauze 
anode,  with  a  current  of  5  amperes.  The  time  required  for  elec- 
trolysis is  from  thirty  to  forty-five  minutes,  depending  upon  the 
amount  of  Pb  present.  Test  the  solution  for  complete  depo- 
sition of  Pb  by  washing  the  watch  glasses  and  sides  of  the  beaker 
until  the  depth  of  the  solution  is  increased  about  0.5  inch.  Then 
continue  the  current  for  fifteen  minutes,  and  if  the  newly  exposed 
surface  is  still  bright,  the  Pb  is  completely  deposited.  Wash  the 
anode  three  or  four  times  with  distilled  water,  once  with  alcohol 
and  then  dry  in  the  oven,  or  on  the  hot  plate,  at  210°  C.  for  0.5 
hour  and  weigh  as  PbCb. 

The  weight  of  PbCb  in  milligrams,  divided  by  100,  will  give  the 
percentage  of  Pb.  The  PbC>2  deposit  can  be  readily  removed  by 
covering  the  anode  with  dil.  HNOs  and  inserting  a  piece  of  Cu. 

Lead  (Alternative  "  Lead  Acid  "  Method)  .—Place  in  a  350  cc. 
beaker  25,  15,  10  or  5  grams  of  drillings  or  sawings,  according  to 
whether  the  spelter  is  of  Grade  A,  B,  C,  or  D,  respectively,  and  add, 
according  to  the  size  of  sample  taken,  300,  180,  120  or  60  cc.  of 
"  lead  acid."*  After  all  but  about  1  gram  of  Zn  is  dissolved,  filter 
on  a  close  filter  and  wash  out  the  beaker  twice  with  "  lead  acid  " 
from  a  wash  bottle.  Wash  the  undissolved  matter  from  the 
filter  into  the  original  beaker  with  water  and  dissolve  with  a  small 
amount  of  hot  HNO3  (1  :  1).  Add  40  cc.  of  "  lead  acid/'  and 
evaporate  on  the  hot  plate  until  strong  fumes  of  SOs  escape.  When 
cool,  add  35  cc.  of  water  (which  is  the  quantity  of  water  evaporated 

*  "  Lead  acid  "  is  a  solution  of  one  volume  of  H2SO4  in  seven  volumes  of 
water,  saturated  with  PbSO4.  It  is  prepared  as  follows:  Pour  300  cc.  of  cone. 
H2SO4  into  1800  cc.  of  water;  dissolve  1  gram  of  lead  acetate  in  300  cc.  of 
water  and  add  to  the  hot  solution  with  stirring.  Let  the  solution  settle  for 
several  days  and  siphon  off  through  a  thick  asbestos  filter  for  use.  When 
"  lead  acid  "  is  used,  it  is  unnecessary  to  consider  the  solubility  of  PbSO4, 
since  the  solution  is  always  brought  back  to  the  same  volume  as  the  volume 
of  "  lead  acid  "  originally  added;  consequently  when  the  PbSO4  is  filtered, 
no  more  lead  remains  in  the  filtrate  than  was  originally  added  in  the  "  lead 
acid." 


ANALYSIS  OF  METALS  139 

from  the  "  lead  acid  ")>  and  heat  to  boiling.  Add  the  first  filtrate 
(containing  the  greater  part  of  the  zinc,  and  possibly  a  small 
amount  of  PbSO4),  stir  well,  and  let  stand  for  at  least  five  hours, 
preferably  overnight.  Filter  on  a  Gooch  crucible,  wash  with 
"  lead  acid,"  then  with  a  mixture  of  equal  parts  of  alcohol  and 
water,  and  finally  with  alcohol  alone.  Set  the  Gooch  crucible 
inside  a  porcelain  crucible  in  order  to  avoid  reduction  of  PbSO4 
by  the  flame  gases  and  mechanical  disintegration  of  the  asbestos 
mat.  Ignite  for  five  minutes  at  the  full  heat  of  a  Tirrill  burner. 
Cool  and  weigh  as  PbSCX.  Calculate  to  Pb. 

CALCULATION.— PbSO4  X  0.6833  =  Pb. 

Iron. — Place  25  grams  of  the  sample  in  a  tall  700  cc.  beaker 
and  dissolve  cautiously  in  125  cc.  of  cone.  HNOs.  Boil,  dilute  to 
about  300  cc.,  add  10  grams  of  NUiCl  and  then  NILjOH  until 
precipitated  Zn(OH)2  has  redissolved.  Boil,  let  settle  and  filter 
on  an  11  cm.  S.  <fe  S.  "  Back  Ribbon  "  or  similar  filter  paper. 
Wash  with  dil.  NELjOH  and  with  hot  water.  Dissolve  the  pre- 
cipitated Fe(OH)3  with  hot  H2SO4  (1  :  4);  wash  with  hot  water; 
dilute  the  filtrate,  if  necessary,  so  that  it  will  contain  about  5% 
of  H2SO4  and  pass  through  the  Jones  reductor.*  Wash  first  with 
150  cc.  of  5%  H2S04  and  then  with  100  cc.  of  water  and  titrate 
with  KMn(>4  solution,  containing  approximately  0.2  gram  per 
liter.  1  cc.  of  KMnC>4  solution  will  equal  about  0.000334  gram  of 
Fe.  Run  a  "  blank  "  with  the  same  amounts  of  acid  and  water 
and  correct  accordingly. 

Standardization. — Standardize  the  KMnC^  against  sodium 
oxalate  obtained  from  the  Bureau  of  Standards,  using  the  following 
procedure:  Weigh  in  duplicate  0.0200  gram  portions  of  Na2C2C>4 
into  a  200  cc.  Erlenmeyer  flask,  dissolve  in  50-75  cc.  of  hot  water 
(80-90°  C.),  and  add  10  cc.  of  H2S04  (1:1).  Titrate  at  once 
with  the  KMnC>4  solution  to  be  standardized,  stirring  vigorously 
and  continuously.  About  49-50  cc.  of  KMnC^  solution  will 
probably  be  required.  The  KMnC>4  must  not  be  added  more 
rapidly  than  10-15  cc.  per  minute  and  the  last  0.5-1  cc.  must  be 
added  with  particular  care  to  allow  each  drop  to  be  fully  decolor- 
ized before  the  next  is  added.  The  solution  should  not  be  below 

*  For  manipulation  of  the  Jones  reductor  see  page  148.  If,  before  passing 
the  solution  through  the  reductor,  a  large  amount  of  PbSO4  is  present,  it  is 
well  to  filter  it  off  so  as  to  prevent  clogging  the  reductor. 


140  TECHNICAL  METHODS  OF  ANALYSIS 

60°  C.  at  the  time  the  end  point  is  reached.  The  use  of  a  small 
thermometer  as  a  stirring  rod  will  be  found  convenient  in  this 
titration. 

0.0167 

CALCULATION. — Fe  factor  = . 

cc.  KMn04  used 

Cadmium. — Place  25  grams  of  drillings  in  a  tall  500  cc.  beaker; 
add  250  cc.  of  water  and  55  cc.  of  cone.  HC1  and  stir.  When 
action  has  almost  ceased,  add  more  acid  with  stirring,  using  about 
2  cc.  at  a  time,  and  letting  stand  after  each  addition  of  acid,  until 
finally  all  but  about  2  grams  of  Zn  has  been  dissolved.  About 
60  cc.  of  acid  in  all  are  usually  required.  It  is  best  to  allow  the 
first  55  cc.  of  acid  to  act  overnight. 

Filter,  first  transferring  one  of  the  undissolved  pieces  of 
zinc  to  the  filter  paper,  and  wash  twice  with  water.  Discard  the 
filtrate.  Wash  the  undissolved  matter  on  the  filter  paper  into  a 
500  cc.  beaker;  cover,  and  dissolve  in  HNOs.  Transfer  to  a 
casserole,  add  20  cc.  of  H2S04  (1:1)  and  evaporate  until  fumes  of 
80s  appear.  Take  up  with  about  100  cc.  of  water,  boil,  cool,  and 
let  stand  until  any  PbSO^  present  settles  completely.  Filter  off 
the  PbSC>4,  wash  with  water,  retain  the  filtrate  and  discard  the 
PbSO4.  Dilute  the  filtrate  to  400  cc.,  add  about  10  grams  of 
NELiCl,  and  pass  in  H^S  for  one  hour.  It  is  occasionally  necessary 
to  start  precipitation  of  the  CdS  by  the  addition  of  a  drop  or  two 
of  NELiOH  to  the  dilute  solution. 

Let  stand  until  the  precipitate  has  settled,  and  then  filter  off 
the  impure  CdS  in  a  loose-bottomed  Gooch  crucible.  Remove 
the  CdS  by  carefully  punching  out  the  bottom  into  a  tall  200  cc. 
beaker.  Wipe  off  any  CdS  remaining  on  the  sides  of  the  crucible, 
using  a  little  asbestos  pulp;  add  60  cc.  of  H2SO4  (1:5)  and  boil 
for  0.5  hour.  In  the  case  of  spelters  carrying  large  amounts  of 
Cd,  it  may  be  necessary  to  add  more  acid.  The  dilute  acid  dis- 
solves CdS  and  ZnS,  but  not  PbS. 

Filter  and  dilute  to  300  cc. ;  add  about  5  grams  of  NKiCl  and 
precipitate  with  H^S  again,  in  order  to  get  rid  of  traces  of  Zn. 
In  case  a  large  amount  of  Cd  is  present,  a  third  precipitation  may 
be  necessary.  After  the  final  precipitation,  let  settle,  filter  and 
transfer  to  a  weighed  platinum  dish;  cover,  and  dissolve  in  HC1 
(1  :  3).  Also  dissolve  the  sulfide  remaining  on  the  filter  paper  in 
hot  HC1  (1  :  3)  and  add  it  to  solution  in  the  platinum  dish.  Add 


ANALYSIS  OF  METALS  141 

a  little  H2S04  and  evaporate  the  solution  on  the  hot  plate  until 
copious  SOs  fumes  escape.  Dilute  with  water,  add  a  few  cc.  of 
cone.  HNOs  to  oxidize  any  filter  paper  shreds,  and  again  evap- 
orate the  solution  until  fumes  of  SOs  come  off  freely.  Remove  the 
excess  of  H^SCX  by  heating  the  dish  cautiously,  and  finally  heat 
to  between  500°  and  600°  C.,  or  to  dull  redness,  and  weigh  as 
CdSO4.  Calculate  to  Cd. 

CALCULATION.—  CdSO4  X  0.5392  =  Cd. 

Cadmium  (Alternative  Method).  —  Proceed  as  above  until  the 
CdS  has  been  dissolved  in  HC1.  Oxidize  with  HNOs  and  filter 
from  any  sulfur.  Transfer  the  solution  to  a  200  cc.  beaker,  add  a 
drop  or  two  of  phenolphthalein  and  then  pure  NaOH  or  KOH 
solution  until  a  permanent  red  color  is  obtained.  Add  a  strong 
solution  of  pure  KCN,  with  constant  stirring,  until  the  precipitate 
of  Cd(OH)2  is  completely  redissolved.  Avoid  using  excess  of  KCN. 
Dilute  the  solution  to  200  cc.  and  electrolyze  with  a  current  of 
5  amperes,  using  a  rotating  platinum  anode  or  cathode.  (The  Cd 
deposits  on  the  cathode.)  The  time  required  is  one  to  two  hours. 
The  solution  should  always  be  tested  for  Cd  as  follows:  Raise 
the  liquid  in  the  beaker  *  and  then  note  after  twenty  minutes 
the  newly  exposed  surface  of  the  electrode.  If  it  is  still  bright 
the  Cd  is  completely  deposited.  Finally  wash  the  electrode  with 
distilled  water  and  then  with  alcohol.  Dry  at  100°  C.,  coo'  and 
weigh.  The  increase  is  metallic  Cd. 

REFERENCES.  —  Report  of  Sub-committee  of  Division  of  Industrial  Chem- 
ists and  Chemical  Engineers.  J.  Ind.  Eng.  Chem.  7,  547  (June,  1915). 

ZINC  DUST 

General.  —  Commercial  zinc  dust  is  bought  and  sold  upon  its 
actual  reducing  power,  which  is  measured  by  the  amount  of 
metallic  Zn  present  or,  as  it  is  termed  in  the  trade,  "  available 
zinc." 

The  determination  of  the  amount  of  available  Zn,  by  means  of 
K2Cr2O7,  and  H2SO4,  depends  upon  the  following  reaction  : 


Standardization  of    Solution.  —  Prepare   a   solution   of    pure 
containing  about  40  grams  per  liter.     Pipette  exactly 
*  As  under  "  Lead  (Electrolytic  Method)  "  above. 


142  TECHNICAL  METHODS  OF  ANALYSIS 

10  cc.  of  this  solution,  with  certified  pipette,  into  an  Erlenmeyer 
flask.  Add  about  150  ce.  of  water,  3  cc.  of  cone.  H2SO4  and  15  cc. 
of  10%  KI  solution.  Titrate  the  liberated  iodine  with  0.1  N  thio- 
sulfate,  adding  a  little  starch  indicator  when  the  end  point  has 
been  nearly  approached.  The  exact  end  point  is  indicated  by  a 
change  in  color  from  dark  brownish  green  to  clear  light  green. 
This  change  is  very  sharp.  Calculate  the  exact  strength  of  the 
bichromate  solution  from  the  factor:  1  cc.  0.1  N  thiosulfate 
=  0.004903  gram  K2Cr2O7. 

NOTE. — It  is  possible  to  obtain  K2Cr2O7  sufficiently  pure  so  that  the 
solution  does  not  need  to  be  standardized. 

Procedure. — Weigh  accurately  1  gram  of  zinc  dust  into  a  350 
cc.  beaker,  add  50  cc.  of  standard  K2Cr2O7  solution  and  dilute 
with  about  200  cc.  of  distilled  water.  Then  add,  drop  by  drop, 
with  constant  stirring,  20  cc.  of  dilute  H2SO4  at  the  rate  of  1  cc. 
per  minute.  It  is  very  important  that  the  liquid  should  be  con- 
stantly stirred  and  no  bubbles  of  hydrogen  should  escape.  Finally, 
add  5  cc.  of  cone.  H2S04  and  let  stand  until  there  is  no  further 
action.  There  will  generally  be  more  or  less  metallic  Pb  which 
will  not  be  attacked.  Heat  just  to  boiling  and  then  cool  to  room 
temperature.  Transfer  the  iquid  to  a  500  cc.  flask  and  dilute 
exactly  to  the  mark.  Mix  thoroughly  and  pipette  200  cc.  into  a 
beaker;  add  15  cc.  of  10%  KI  solution  and  titrate  with  0.1  N 
thiosulfate  as  previously  described.  Calculate  the  amount  of 
K2Cr2C>7  equivalent  to  the  thiosulfate  titration  and  multiply  by 
2.5.  Subtract  this  from  the  total  amount  of  K2Cr20?  in  the 
50  cc.  originally  taken  and  from  the  difference  calculate  the  amount 
of  metallic  Zn. 

CALCULATION.— K2Cr2O7  X  0.6666  =  Zn. 

REFERENCE.  —  Classen  :  "  Ausgewahlte  Methoden  der  Analytischen 
Chemie,"  Vol.  1,  page  353. 

BRASS  AND  BRONZE 

General. — This  method  covers  the  analysis  of  alloys  of  the 
brass  or  bronze  type  containing  two  or  more  of  the  following 
elements:  Cu,  Pb,  Sn,  Zn,  P,  Fe,  Ni,  Mn,  As,  Sb,  and  Al  (the 
latter  only  in  small  amounts).  It  does  not  include  white  metals 


ANALYSIS  OF  METALS  143 

and  aluminum  alloys,  containing  considerable  Al.  The  sample 
for  analysis  should  be  in  the  shape  of  very  fine  drillings  free  from 
oil,  iron,  dirt,  or  other  foreign  matter.  If  the  composition  of  the 
alloy  is  unknown,  a  qualitative  analysis  should  be  made,  using  a 
5-gram  sample. 

In  those  cases  where  an  alternative  method  is  given,  the  latter 
is  to  be  used  only  when,  on  account  of  lack  of  chemicals  or  appa- 
ratus, the  first  method  cannot  be  employed. 

Phosphorus. — Dissolve  1  gram  of  the  sample  in  15  cc.  of  fum- 
ing HNOs  and  evaporate  on  the  hot  plate  until  most  of  the  free 
acid  is  expelled.  Add  10  cc.  of  cone.  HC1  and  evaporate  to  dry- 
ness.  Dissolve  the  residue  in  10  cc.  of  HC1  and  50  cc.  of  water, 
heat  to  boiling  and  precipitate  the  Pb,  Sn,  and  Cu  with  granulated 
c.  P.  metallic  Zn,  20-mesh.  Use  an  excess  of  the  Zn  and  let  the 
reaction  continue  until  no  Pb,  Sn,  or  Cu  remains  in  the  solution. 
Just  before  filtering  add  5-10  cc.  of  cone.  HC1  to  the  solution. 
Filter  immediately  on  a  rapid  filter,  in  the  cone  of  which  has  been 
placed  1-2  grams  of  c.  P.  granulated  20-mesh  zinc.  Wash  well 
with  hot  water  and  neutralize  this  solution  (approximately  150  cc. 
in  volume)  with  NH^OH,  adding  the  latter  only  until  a  permanent, 
heavy,  curdy,  white  precipitate  forms.  Bring  back  again  with 
cone.  HNOs,  adding  approximately  5  cc.  in  excess.  Heat  the 
solution  to  70°  C.  and  precipitate  the  phosphorus  by  adding  60  cc. 
of  ammonium  molybdate  solution.  Shake  for  five  minutes  and 
let  the  solution  stand  at  least  0.5  hour,  or  until  the  yellow  precip- 
itate has  completely  settled.  Filter  through  an  11  cm.  filter  paper, 
wash  the  precipitate  five  times  with  2%  HN03,  then  with  1% 
KNOs  solution  until  free  from  acid  (approximately  fifteen 
times) . 

Place  the  filter  and  contents  in  the  original  flask,  which  has 
been  thoroughly  rinsed  with  water,  and  add  approximately  50  cc. 
of  cool  distilled  water  and  a  measured  amount  of  standard  NaOH 
from  a  burette,  5  cc.  at  a  time  (sufficient  to  completely  dissolve  the 
yellow  precipitate).  Cork  the  flask  and  agitate  violently  until 
the  filter  paper  is  disintegrated;  add  3  drops  of  1%  phenolphtha- 
lein  solution  with  a  medicine  dropper,  and  titrate  with  standard 
HNOs  to  the  disappearance  of  the  pink  color.  The  same  standard 
acid  and  alkali  may  be  used  as  employed  for  determining  Phos- 
phorus in  Steel,  as  described  on  page  113. 


144  TECHNICAL  METHODS  OF  ANALYSIS 

CALCULATION.— Subtract  the  number  of  cc.  of  HNO3  used 
from  the  number  corresponding  to  the  volume  of  NaOH  added. 
The  difference  is  the  cc.  of  HNO3  equivalent  to  the  phosphorus  in 
the  sample,  and  this,  multiplied  by  the  value  of  the  HNO3  in  terms 
of  phosphorus,  gives  the  weight  of  phosphorus  in  the  sample. 
This  weight  multiplied  by  100  gives  the  per  cent  of  phosphorus. 

Tin. — (a)  If  the  alloy  contains  over  1.5%  of  Sn:  Weigh  1  gram 
into  a  250  cc.  beaker,  add  15  cc.  of  dil.  HN03  (2:1),  cover  imme- 
diately with  a  watch  glass  and,  when  violent  action  ceases,  boil 
until  no  more  red  fumes  are  given  off.  Place  the  beaker  on  a 
water  bath  and  digest  for  one-half  hour.  Dilute  with  50  cc.  of 
water  and  filter  at  once,  if  the  alloy  contains  phosphorus,  washing 
very  thoroughly  with  2%  HN03. 

Test  the  last  drops  of  the  filtrate  with  a  little  potassium  ferro- 
cyanide  or  ammonium  sulfide  solution;  neither  solution  should 
give  any  precipitate.  Place  the  filter  paper  and  contents  in  a 
weighed  porcelain  crucible,  smoke  off  the  paper  and  ignite  for  fif- 
teen minutes  in  the  full  heat  of  a  Tirrill  burner.  Cool  in  a  desic- 
cator and  weigh.  This  represents  Sn02-fSb204+P2O5,  together 
with  traces  of  Fe,  Cu  and  Pb.  (Save  these  mixed  oxides.)  The 
phosphorus  and  antimony  are  separately  determined,  as  below, 
and  subtracted  from  the  above  weight.  The  remainder  is  SnO2. 
Calculate  to  Sn. 

CALCULATION.— SnO2  X0.7877  =  Sn. 

(b)  If  the  alloy  contains  less  than  1 .5%  of  Sn:  Dissolve  5  grams 
in  40  cc.  of  HNO3  (2:1)  and  treat  as  above  described.  In  this 
case  the  filtrate  should  be  made  up  to  volume  and  an  aliquot 
equivalent  to  1  gram  taken  for  the  subsequent  determinations  of 
Cu,  Pb  and  Zn. 

NOTE. — In  the  case  of  brass  or  bronze  containing  less  than  10%  tin  and  less 
than  0.7%  phosphorus,  no  further  purification  of  the  mixed  oxides  is  necessary; 
but  if  above  these  limits,  the  mixed  oxides  must  be  purified  as  follows :  Fuse  the 
ignited  precipitate  with  a  mixture  of  finely  powdered  sulfur  and  Na2CO3  in  the 
proportion  of  1  part  of  the  precipitate  to  3  parts  each  of  sulfur  and  of  Na2CO3  in 
a  covered  porcelain  crucible  until  the  odor  of  SO2  has  disappeared.  Cool  and 
dissolve  the  fusion  in  hot  water;  add  an  excess  of  NaaSOs  to  convert  any 
polysulfides  to  monosulfides,  filter  and  wash  the  precipitate  thoroughly. 
This  precipitate  contains  Cu,  Pb,  and  Fe.  Dissolve  in  dil.  HNO3  (1  :  3). 
Determine  the  Cu  and  Pb  electrolytically  and  the  Fe  with  NH4OH  in  the 
regular  way.  Calculate  the  weights  thus  found  to  the  oxides  and  subtract 
from  the  original  precipitate. 


ANALYSIS  OF  METALS  145 

CALCULATIONS.—       P  X  2.2886  =  P205. 
SbXl.2662  =  Sb2O4. 
PbO2X0.9331  =  PbO. 
FeX  1.4298  =  Fe203. 
CuX  1.2517  =  CuO. 

Copper  and  Lead. — (a)  When  lead  is  10%  or  less:  Dilute  the 
filtrate  from  the  Sn  determination  to  approximately  200  cc.  and 
add  cone.  HNOs  until  the  solution  contains  approximately  10%. 
Then  add  1  cc.  of  cone.  H2SC>4.  Electrolyze  the  solution  in  a 
beaker,  starting  with  2  amperes  current  and  gradually  working 
up  to  3,  as  the  blue  color  of  the  solution  disappears.  Use  either 
a  rotating  anode  or  a  rotating  cathode  and  continue  the  electrolysis 
for  forty-five  minutes.  At  the  end  of  this  time  stop  the  rotation 
of  the  electrode  but  do  not  turn  off  the  electrolysis  current.  Lower 
the  beaker  and  shut  off  the  current  just  before  the  electrodes  come 
out  of  the  solution.  Quickly  wash  the  electrodes  with  a  stream  of 
distilled  water  from  a  wash  bottle.  Remove  and  immerse  imme- 
diately in  methyl  alcohol.  Then  burn  off  the  alcohol  in  the  air 
keeping  the  electrode  in  constant  motion.  Cool  in  a  desiccator 
and  weigh.  The  cathode  contains  the  Cu  in  the  metallic  state  and 
the  anode  contains  the  Pb  as  Pb02. 

Test  the  solution  for  complete  removal  of  Cu  and  Pb  by 
further  electrolysis  with  fresh  electrodes  and  weigh  any  further 
deposit  which  may  form. 

CALCULATION.— PbO2  X  0.8643  =  Pb.* 

NOTES. — (1)  In  case  no  Pb  is  present,  the  addition  of  4  cc.  of  cone.  H2SO4 
before  electrolyzing  aids  materially  in  getting  a  good  copper  desposit. 

(2)  Extreme  care  must  be  exercised  that  the  electrodes  are  completely 
dry  before  weighing.     The  alcohol  should  be  changed  frequently,  as  it  soon 
absorbs  water  and  drying  becomes  difficult. 

(3)  In  case  there  is  only  a  trace  of  Pb  present,  a  separate  5-gram  sample 
should  be  run  for  this  element  alone. 

(b)  In  the  case  of  alloys  containing  more  than  10%  of  Pb 
the  PbO2  is  likely  to  flake  off  the  anode  and  electrolysis  is  not  a 
suitable  method.  Proceed  therefore  as  follows: 

To  the  filtrate  from  the  Sn  determination,  add  10  cc.  of  cone. 
H2S04.  Evaporate  the  solution  until  fumes  of  80s  come  off 
*  Empirical  factor  (page  137). 


146  TECHNICAL  METHODS  OF  ANALYSIS 

freely.  Then  cool  thoroughly  and  add  150  cc.  of  water;  boil  and 
let  stand  until  perfectly  cool.  Filter  the  PbSC^  on  a  weighed 
Gooch  crucible,  and  wash  with  a  5%  solution  of  H2SO4,  and  then 
with  a  mixture  of  equal  parts  of  alcohol  and  water  until  the 
washings  are  free  from  acid.  The  alcohol  should  not  be  run  into 
the  main  filtrate  as  it  will  interfere  with  the  subsequent  elec- 
trolysis for  Cu.  It  is  used  merely  to  remove  the  acid  of  the  first 
washing  liquid. 

•  Dry  in  the  oven  to  remove  alcohol  and  moisture,  then  set 
the  Gooch  crucible  inside  of  a  platinum  crucible  and  ignite  to  a 
dull  red  heat.  Cool  in  a  desiccator  and  weigh  as  PbSO.*.  Cal- 
culate to  Pb. 

CALCULATION.— PbSO4  X  0.6833  =  Pb. 

NOTE. — In  case  this  procedure  is  followed,  the  Cu  is  determined  by  elec- 
trolysis of  the  filtrate  as  above  described. 

Zinc. — To  the  filtrate  *  from  the  Cu  and  Pb  determinations 
add  5  cc.  (not  more)  of  cone.  H2SO4  and  evaporate  to  the  appear- 
ance of  80s  fumes.  Cool,  rinse  into  a  suitable  beaker,  and  dilute 
to  approximately  150  cc.  Add  50  cc.  of  30%  NaOH  solution  and 
electrolyze  the  solution,  using  a  current  of  3  amperes  and  2.5  volts, 
and  a  cathode  which  has  been  plated  with  Cu.  The  cathode  used 
previously  in  the  determination  of  Cu  is  very  suitable.  The  Zn 
generally  deposits  out  in  fifteen  minutes.  After  weighing  the 
deposit,  however,  dissolve  off  the  Zn  in  HC1  (1:1),  wash,  dry  and 
weigh ;  then  electrolyze  for  ten  minutes  more  in  the  same  solution 
to  insure  the  complete  removal  of  all  Zn.  The  manipulation  for 
this  determination  is  exactly  as  in  the  Cu  determination  and  the 
Zn  is  weighed  as  metallic  zinc. 

NOTES. — (1)  The  amount  of  zinc  weighed  on  the  electrode  should  not  be 
over  0.1  gram.  If,  therefore,  the  alloy  contains  more  than  10%  of  Zn,  dilute 
the  filtrate  from  the  Cu  and  Pb  determinations  to  a  suitable  volume  in  a  volu- 
metric flask  and  take  an  aliquot  that  will  yield  not  more  than  0.1  gram  of  Zn. 

(2)  If  Pb  has  been  determined  as  PbSO4  and  10  ccy  of  H2SO4  used,  add 
25  cc.  more  of  the  30%  NaOH  solution  to  take  care  of  the  extra  acid. 

(3)  Blanks  should  be  run  frequently  on  the  NaOH  to  make  sure  that  it 
contains  no  Zn.     J.  T.  Baker's  c.  p.  NaOH  (electrolytic)  has  been  found  satis- 
factory. 

*0r  to  an  aliquot.     (See  Note  1.) 


ANALYSIS  OF  METALS  147 

Zinc  (Alternative  Method). — In  the  nitrate  from  the  electrol- 
ysis of  Cu  and  Pb  precipitate  the  Fe  and  Al  as  hydroxides  by  the 
addition  of  an  excess  of  NHiOH.  Filter  and  determine  Zn  in  the 
nitrate  as  follows: 

Add  cone.  HC1  to  the  above  solution  until  it  is  faintly  acid, 
then  add  2  cc.  in  excess.  Now  add  an  excess 'of  a  10%  solution 
of  NEU  or  Na  phosphate  and  heat  to  boiling.  Add  NELiOH 
rapidly  until  all  the  precipitate  redissolves.  Bring  back  to  acidity 
slowly  with  acetic  acid  and  add  1  cc.  excess.  Stir  briskly,  care 
being  exercised  that  the  policeman  does  not  touch  the  sides  of  the 
beaker,  until  the  precipitate  becomes  crystalline.  Set  the  beaker 
aside  for  several  hours,  filter  on  a  weighed  Gooch  crucible,  wash 
with  hot  water,  ignite  and  weigh  as  Zn2P2O7.  Calculate  to  Zn. 

CALCULATION.— Zn2P207  X  0.4289  =  Zn. 

Manganese. — Dissolve  10  grams  in  70  cc.  of  HNOs  (1  :  1), 
adding  only  a  small  amount  of  acid  at  a  time  to  avoid  loss  by  foam- 
ing. Evaporate  to  approximatly  half  volume.  Add  30-40  cc. 
of  water,  filter  off  any  Sn02  and  wash  the  precipitate  thoroughly 
with  hot  water.  In  case  both  Mn  and  Fe  are  desired,  make  up 
the  solution  to  volume,  retaining  one-half  for  the  determination 
of  Fe  and  the  remainder  for  the  Mn. determination.  Most  sam- 
ples of  so-called  manganese  bronze  contain  a,  very  small  amount 
of  Mn,  in  which  case  take  an  aliquot  representing  5  grams.  In  no 
case,  however,  should  the  aliquot  taken  for  analysis  contain  over 
0.015  gram  of  Mn.  Remove  the  Cu  and  Pb  by  electrolysis  and 
evaporate  to  50-75  cc.;  cool  to  tap  water  temperature  and  add 
approximately  0.5  gram  of  sodium  bismuthate.  Let  stand  for 
several  minutes  with  occasional  shaking.  Place  an  alundum 
filtering  tube  in  a  Gooch  crucible  holder,  making  the  connection 
with  rubber.  Filter  the  solution  through  the  alundum  with  suc- 
tion. The  alundum  tube  should  fit  well  down  into  the  glass  cru- 
cible holder  and  the  solution  should  at  no  time  come  within  0.5 
inch  of  the  place  where  the  rubber  connection  is  made  on  the  out- 
side of  the  tube.  Titrate  the  filtered  solution  at  once  with  stand- 
ard sodium  arsenite  solution. 

NOTE. — The  arsenite  solution  is  made  to  contain  approximately  1  gram 
As2O3  per  liter.  The  solution  described  under  Manganese  in  Steel  on  page  111, 
is  satisfactory. 


148  TECHNICAL  METHODS  OF  ANALYSIS 

Manganese  (Alternative  Method). — In  case  the  estimations 
of  Sn  and  Mn  only  are  desired,  evaporate  the  filtrate  from  the  Sn 
determination  to  small  bulk.  Add  50  cc.  of  cone.  HNOs  (which 
must  be  water-white)  and  bring  to  a  boil.  Add  2-3  grams  of 
KClOs,  a  few  crystals  at  a  time,  and  boil  until  the  Mn(>2  is  com- 
pletely precipitated  and  all  nitrous  fumes  are  driven  off.  Filter 
through  a  Gooch  crucible  and  wash  free  from  add  with  hot  water, 
allowing  all  HNOs  to  run  through  the  filter  before  starting  to  wash 
with  water.  Transfer  the  asbestos  and  precipitate  to  the  original 
flask  and  add  a  measured  excess  of  standard  ferrous  ammonium 
sulfate  solution,  5  cc.  at  a  time.  Agitate  until  the  brown  MnO2  is 
dissolved.  It  may  be  necessary  to  break  up  some  of  the  lumps 
with  a  stirring  rod  before  solution  is  possible.  Now  titrate  the 
excess  of  ferrous  iron  to  a  pink  color  with  standard  KMn04. 
(The  same  standard  ferrous  ammonium  sulfate  and  KMn(>4 
solutions  may  be  used  as  are  used  for  the  determination  of  Chro- 
mium in  Steel,  page  122.)  Deduct  from  the  amount  of  ferrous 
ammonium  sulfate  used  (expressed  in  terms  of  the  KMn04  solu- 
tion) the  amount  of  KMnCU  required  for  the  back  titration.  The 
difference  is  the  amount  of  standard  KMnCU  solution  consumed  by 
the  Mn  present  in  the  precipitate.  Calculate  the  Mn  factor  of 
the  KMnC>4  solution  by  multiplying  its  Fe  factor  by  0.4919. 

Iron. — Use  a  5-gram  aliquot  from  the  Mn  determination,  or,  in 
case  this  element  is  not  determined,  dissolve  5-10  grams  of  the 
finely  divided  sample  in  HNOs,  boil  until  nitrous  fumes  are  ex- 
pelled and  dilute  with  100  cc.  of  water.  Filter  off  any  meta- 
stannic  acid  and  wash  thoroughly  with  hot  water.  Add  a  small 
amount  of  NILiCl  to  the  filtrate  and  an  excess  of  NH4OH  suf- 
ficient to  redissolve  any  white  Zn(OH)2  formed.  Heat  to  boiling, 
filter  and  wash  the  precipitate  with  hot  water  until  the  washings 
are  free  from  Cu.  Dissolve  in  hot  HC1  (1:1)  and  repeat  the 
process.  After  the  second  precipitation,  dissolve  the  Fe(OH)s  by 
pouring  hot  H2SO4  (1:4)  through  the  filter  paper,  washing  the 
filter  thoroughly  with  the  1  :  4  acid  and  hot  water.  Dilute  until 
the  solution  contains  5%  of  H2S04.  Meanwhile  prepare  the  Jones 
reductor*  as  follows: 

*  The  Jones  reductor  consists  of  a  glass  tube  about  30  cm.  long  and  18  mm. 
inside  diameter  with  a  glass  stopcock  at  the  bottom.  In  filling  it,  first  place 
a  platinum  spiral  or  a  few  glass  beads  in  the  bottom  and  then  a  plug  of  glass 


ANALYSIS  OF  METALS  149 

Connect  the  suction  bottle  with  a  vacuum  pump,  fill  the 
reductor  while  the  stop-cock  is  closed  (or  nearly  so)  with  warm  5% 
H2S04  and  then  open  the  stop-cock  so  that  the  acid  runs  through 
slowly.  Continue  to  pour  acid  in  until  200  cc.  have  passed  through, 
then  close  the  cock  while  a  small  quantity  of  liquid  is  still  left  in  the 
funnel.  Remove  the  filtrate  and  again  pass  through  100  cc.  of 
warm  5%  acid.  Test  this  with  0.1  N  KMnO4  solution.  A  single 
drop  should  color  it  permanently;  if  it  does  not,  repeat  the  wash- 
ing. Be  sure  that  no  air  enters  the  reductor.  (If  it  is  impos- 
sible to  obtain  an  acid  solution  which  does  not  color  with  1  drop 
of  KMnC>4  solution,  the  entire  filtrate  may  be  titrated  and  the 
determination  used  as  a  negative  "  blank  "  in  the  determination.) 

Pour  the  acid  iron  solution  while  hot  (but  not  boiling)  through 
the  reductor  at  a  rate  not  exceeding  50  cc.  per  minute.  Wash 
out  the  beaker  with  5%  H^SCU  and  follow  the  iron  solution  with- 
out interruption  with  175  cc.  of  warm  acid,  and  finally  with 
75  cc.  of  distilled  water,  leaving  the  funnel  partially  filled.  Remove 
the  filter  bottle  and  cool  the  solution  under  the  water  tap.  Add 
10  cc.  of  dil.  H2S04  and  titrate  to  a  faint  pink  with  0.05  N  KMn04 
solution  directly  in  the  filter  bottle.  Calculate  the  titration  to  Fe. 

CALCULATION.— 1  cc.  0.05  N  KMn04  =  0.00279  gram  Fe. 

NOTE. — If  the  alloy  contains  tin,  the  iron  obtained  from  the  purification 
of  the  SnO2  precipitate  must  be  added  to  that  found  in  the  main  solution. 

Arsenic. — Weigh  3-10  grams  of  the  sample  (according  to  the 
amount  of  As  present)  into  a  Kjeldahl  flask;  add  a  solution  of 
FeCls  (made  by  dissolving  20  grams  Fe20s  in  150  cc.  cone.  HC1) ; 
distill  slowly,  collecting  the  distillate  in  a  liter  Erlenmeyer  flask. 
When  the  distillation  is  complete  (after  two-thirds  of  the  solution 
has  distilled  over)  neutralize  the  distillate  with  stick  NaOH  or 
strong  NaOH  solution;  acidify  again  with  HC1  and  bring  back 
until  faintly  alkaline  with  NaHCOs  solution  (the  solution  must  be 

wool  followed  by  a  thin  layer  of  asbestos  such  as  is  used  for  Gooch  crucibles. 
Finally  fill  the  tube  with  amalgamated  zinc  to  within  about  5  cm.  of  the  top 
and  cover  it  with  a  little  glass  wool  serving  as  a  filter. 

The  amalgamated  zinc  may  be  prepared  as  follows:  Dissolve  5  grams  of 
mercury  in  25  cc.  of  HNO3  (1  '.  1),  dilute  to  250  cc.  and  transfer  to  a  heavy 
liter  flask.  Add  to  the  solution  50  grams  of  granulated  zinc  (20-30-mesh 
size),  shake  the  mixture  thoroughly  for  1-2  minutes  and  then  pour  off  the 
solution  and  wash  the  zinc  free  from  acid  with  distilled  water. 


150  TECHNICAL  METHODS  OF  ANALYSIS 

kept  cool  during  this  process) ;  add  a  few  drops  of  starch  solution 
and  titrate  with  0.01  N  iodine  solution;  calculate  to  As. 

A  "  blank  "  distillation  should  always  be  made,  using  the 
same  amount  of  reagents  but  omitting  the  sample.  The  titration 
obtained  on  the  "  blank  "  should  be  subtracted  from  that  required 
by  the  sample. 

The  iodine  solution  must  always  be  freshly  standardized 
against  pure  As203  and  the  factor  thus  obtained. 

Standard  0.01  N  Iodine  Solution.— Dissolve  1.27  grams  of 
resublimed  iodine  and  2  grams  of  KI  in  200  cc.  of  water  in  a  cas- 
serole. When  the  solution  is  complete,  transfer  to  a  graduated 
flask  and  dilute  to  1  liter.  (Or,  dilute  100  cc.  of  the  laboratory 
stock  solution  of  0.1  N  iodine  to  1  liter.)  Standardize  the  solu- 
tion against  c.  P.  As2C>3  as  follows: 

Weigh  out  0.1000  gram  of  As203  into  a  small  beaker,  dissolve 
in  NaOH  solution  (2-3  grams  of  NaOH  and  10  cc.  of  H2O). 
Dilute  to  250  cc.  in  a  volumetric  flask  with  CO2-free  distilled 
water.  Acidify  50  cc.  of  this  stock  solution  with  5  cc.  of  cone. 
HC1  and  then  make  slightly  alkaline  with  NaHCOs.  Titrate  with 
the  iodine,  using  starch  as  an  indicator.  Calculate  the  arsenic 
•  factor  of  the  solution. 

0.00757 

CALCULATION. — As  factor  =— — ,. 

cc.  Iodine  required 

Antimony. — Dissolve  5-10  grams  of  the  sample  in  a  500  cc. 
Erlenmeyer  flask  in  30  cc.  of  cone.  HNOs.  Add  sufficient  pure  tin 
so  that  the  ratio  Sn  :  Sb  is  at  least  3:1,  otherwise  the  Sb  will  not 
be  completely  precipitated.  Evaporate  the  solution  to  10  cc. 
and  then  dilute  with  hot  water  to  250  cc.  Boil  for  fifteen  to 
twenty  minutes  and  then  let  the  precipitate  settle  with  the  flask 
at  an  angle  of  45°.  The  precipitate  should  settle  out  well.  If  it 
does,  carefully  decant  as  much  of  the  solution  as  possible,  but  do 
not  lose  any  of  the  precipitate.  If  the  precipitate  does  not  settle 
out  well,  decant  through  a  Gooch  crucible  and  then  return  the 
precipitate  and  asbestos  to  the  flask.  If  much  Cu  is  present,  it  is 
advisable  to  add  more  hot  water  and  let  settle;  then  decant  again. 
The  object  is  to  get  rid  of  most  of  the  Cu. 

Add  15  cc.  of  cone.  H2SO4  and  4-5  grams  of  K2S(>4  to  the 
flask  and  evaporate  to  white  fumes.  Do  not  drive  off  all  free 
H2S04  so  that  the  melt  becomes  hard  on  cooling.  Then  add  0.5 


ANALYSIS -OF  METALS  151 

gram  of  powdered  tartaric  acid.  Heat  strongly  until  the  solution 
becomes  light  colored,  or  until  all  of  the  carbon  is  destroyed.  If 
necessary,  add  a  little  HN03  and  heat  to  the  appearance  of  80s 
fumes.  This  treatment  leaves  the  Sb  in  the  proper  condition  for 
titration.  Cool,  add  50  cc.  of  water  and  10  cc.  of  cone.  HC1,  and 
heat  to  solution  of  all  that  is  soluble.  Cool  very  thoroughly. 
Add  110  cc.  more  water  and  10  cc.  more  acid.  Cool  again  and 
then  titrate  at  once  with  0.1  N  KMnO4.  The  end  point  is  distinct 
but  it  fades  after  a  short  time.  From  the  known  Sb  factor  of  the 
KMn04  solution,  calculate  the  per  cent  of  Sb. 

NOTE. — The  KMnO4  solution  should  be  standardized  against  c.  p.  anti- 
mony and  the  value  of  the  solution  in  terms  of  Sb  calculated,  then  the  personal 
error  in  the  end  point  will  be  the  same  as  in  the  actual  analysis.  The  same 
KMnO4  solution  may  be  used  as  is  described  under  Antimony  in  White  Metals 
on  page  155.  The  method  of  standardization  is  also  there  described. 

Nickel. — Whenever  a  bronze  is  found  to  contain  over  15%  of 
Pb,  nickel  is  very  apt  to  be  present.  For  the  determination,  add 
5  cc.  of  cone.  H2SO4  to  the  solution  from  which  Cu  and  Pb  have 
been  removed,  and  evaporate  to  SOs  fumes.  Dilute  with  50  cc. 
of  water  and  heat  until  all  soluble  salts  are  dissolved.  Quickly 
pour  this  solution  into  50  cc.  of  30%  NaOH  solution.  Heat  to 
boiling,  whereupon  any  Ni  should  be  precipitated  as  the  apple 
green  Ni(OH)2.  Dilute  the  solution  to  150  cc.,  let  the  precipitate 
settle  and  filter  through  a  weighed  Gooch  crucible.  Wash  thor- 
oughly with  hot  water.  Transfer  the  filtrate  to  the  original  beaker 
and  dissolve  all  the  Ni(OH)2  through  the  Gooch  crucible  with  the 
least  possible  amount  of  warm  dil.  H2SO4.  Wash  the  Gooch 
crucible  thoroughly  and  reprecipitate  the  Ni  by  pouring  the  solu- 
tion into  10  cc.  more  of  30%  NaOH  solution  diluted  to  about  30  cc. 
Heat  to  boiling.  Let  the  precipitate  settle  and  filter  through  the 
same  Gooch  crucib'e.  Wash  with  hot  water,  ignite  at  a  white 
heat  and  weigh  as  NiO.  Calculate  to  Ni. 

CALCULATION.— NiO  X  0.7858  =  Ni. 

NOTE. — If  zinc  is  desired,  and  has  not  already  been  determined,  add  the 
second  filtrate  to  the  first,  evaporate  if  necessary,  and  transfer  to  a  250  cc. 
beaker  for  electrolysis.  Electrolyze  as  previously  described  under  Zinc. 

Aluminum. — This  element  is  best  determined  after  removal  of 
zinc  by  electrolysis.  Acidify  the  solution,  which  is  now  alkaline 


152  TECHNICAL  METHODS  OF  ANALYSIS 

with  NaOH,  with  cone.  HC1  and  precipitate  Fe  and  Al  by  adding  a 
slight  excess  of  NH4OH  and  bringing  to  a  boil.  Let  settle,  filter 
and  wash  thoroughly  with  hot  water.  Ignite  strongly  in  a  platinum 
crucible  and  weigh  as  Fe203+Al203.  Fuse  with  a  considerable 
excess  of  anhydrous  KHS04,  take  up  the  fusion  with  H2O  and  add 
sufficient  cone.  H2S04  to  give  an  acid  concentration  of  5%.  Warm 
the  solution,  pass  through  a  Jones  reductor  and  titrate  the  Fe 
with  0.05  N  KMnCU.  Calculate  to  Fe20s  and  subtract  from  the 
weight  of  combined  oxides  to  obtain  the  AbOs.  Calculate  to  Al. 
CALCULATION.— A12O3  X  0.5303  =  Al. 

NOTE. — Inasmuch  as  the  NaOH  which  has  been  used  for  the  zinc  electrol- 
ysis may  contain  an  appreciable  amount  of  Fe  or  Al,  a  blank  determination 
should  be  made  upon  an  equal  amount  of  NaOH  solution  and  any  Fe  and  Al 
so  obtained  should  be  subtracted. 

REFERENCE.— Price  and  Meade:  "  Technical  Analysis  of  Brass  and  the 
Non-ferrous  Alloys." 


NICKEL  SILVER 

General. — Nickel  Silver  (German  Silver)  is  an  alloy  of  Cu,  Ni 
and  Zn,  containing  occasionally  small  amounts  of  Pb,  Fe,  Mn  and 
other  minor  impurities. 

The  method  of  analysis  here  described  has  been  devised  to 
take  advantage  of  the  well-known  dimethylglyoxime  precipitation 
of  Ni  and  has  given  excellent  satisfaction  in  this  laboratory. 
Repeated  comparisons  with  other  methods  have  demonstrated 
that  it  gives  accurate  results  and  requires  much  less  time  and 
manipulation. 

Copper. — Weigh  1  gram  of  the  alloy  into  a  beaker  and  dissolve 
in  15  cc.  of  HNOs  (1  :  1).  When  solution  is  complete  and  all 
nitrous  fumes  have  been  removed  by  boiling,  dilute  to  a  suitable 
volume  for  electrolysis,  adding  sufficient  cone.  HNOs  to  give 
an  acid  concentration  of  approximately  10%  if  rotating  electrodes, 
or  3%  if  the  stationary  type  is  employed.  When  using  rotating 
electrodes  and  a  10%  acid  concentration,  a  current  density  increas- 
ing from  2  amperes  at  the  beginning  to  3  amperes  near  the  end  of 
the  electrolysis,  works  very  satisfactorily.  In  the  case  of  sta- 
tionary electrodes  and  a  3%  acid  concentration,  a  current  of  0.5 
ampere  is  preferable.  With  rotating  electrodes  it  is  possible  to 


ANALYSIS  OF  METALS  153 

remove  all  copper  in  one  hour.     The  metallic  Cu  is  weighed  as 
such  on  the  electrode  in  the  usual  manner.     (See  page  145.) 

Lead. — Small  amounts  of  Pb  may  be  present  as  an  impurity  in 
the  Zn  used  in  the  alloy.  This  will  be  entirely  deposited  on  the 
anode  as  Pb(>2  and  may  be  weighed  as  such,  calculating  to  metallic 
Pb. 

CALCULATION.— Pb02  X  0.8643  =  Pb.* 

Nickel. — After  the  removal  of  the  Cu  and  any  Pb  present 
transfer  the  solution  to  a  500  cc.  volumetric  flask  and  dilute  to  the 
mark.  Pipette  100  cc.,  representing  0.2  gram,  into  a  600  cc. 
beaker.  Make  slightly  but  distinctly  alkaline  with  NH4OH, 
dilute  to  approximately  400  cc.,  heat  to  incipient  boiling  and  filter 
off  any  Fe(OH)3  precipitate.  In  the  nitrate,  precipitate  nickel 
as  nickel  glyoxime  with  75  cc.  of  saturated  alcoholic  solution  of 
dimethylglyoxime.  Heat  to  slightly  below  boiling  for  one  hour, 
filter  on  a  Gooch  crucible  previously  ignited  and  weighed,  and 
wash  with  hot  water. 

Always  test  the  first  few  cc.  of  the  filtrate  with  a  few  drops  of 
dimethylglyoxime  reagent  to  make  certain  that  no  Ni  remains 
unprecipitated.  If  it  is  found  that  some  Ni  still  remains  in  the  fil- 
trate, return  the  latter  to  the  beaker,  add  a  few  cc.  more  of  the 
reagent,  heat  just  below  boiling  for  fifteen  to  twenty  minutes  more 
and  again  filter.  If  all  Ni  is  now  precipitated,  filter,  wash,  dry  for 
one  hour  at  105-120°  C.,  cool  and  weigh.  Calculate  to  metallic 
Ni  and  multiply  the  result  by  5  to  correct  for  aliquoting. 

CALCULATION. — Nickel  glyoxime  X  0.203 1  =Ni. 

Zinc. — Transfer  the  filtrate  from  the  Ni  precipitate  to  a  beaker 
and  evaporate  until  the  odor  of  NHs  can  no  longer  be  detected. 
Cool  the  solution,  transfer  to  a  500  cc.  Erlenmeyer  flask  to  avoid 
loss  by  spattering,  add  5-6  cc.  of  cone.  H2SO4  and  evaporate  the 
solution  to  the  appearance  of  dense  white  fumes.  Cool  thoroughly 
and  take  up  with  water.  Add  50  cc.  of  30%  NaOH  solution  and 
electrolyze  on  a  copper  coated  electrode  according  to  the  method 
on  page  146.  Weigh  as  metallic  Zn  and  multiply  the  weight 
by  5  to  correct  for  aliquoting. 

Impurities. — The  determination  of  Pb  has  been  already 
described.  Fe,  Mn  and  other  impurities  may  be  determined  as 
in  Brass  and  Bronze  (see  page  142). 

NOTE. — This  method  was  adapted  bv  H.  C.  Parish  of  this  laboratory. 
*  This  is  an  empirical  factor  ^ee  under  Spelter,  page  137). 


154  TECHNICAL  METHODS  OF  ANALYSIS 

WHITE  METALS 

General. — This  method  applies  to  the  analysis  of  white  alloys 
containing  Sb,  Sn,  Cu,  Zn,  Pb,  Fe,  Ni,  Mn,  Al,  and  Mg.  These 
are  most  conveniently  divided  into  (1)  Solders,  (2)  Babbitts, 
(3)  Type  Metals,  and  (4)  Aluminum  Alloys. 

In  those  cases  where  two  methods  are  given  for  the  same 
determination,  the  first  method  is  preferable  and  the  alternative 
method  should  be  used  only  when  made  necessary  by  lack  of  chem- 
icals or  apparatus  for  the  first  method. 

Sampling. — A  representative  sample  is  best  obtained  by  the 
use  of  a  hacksaw.  The  sawdust  from  the  sample  is  especially 
desirable  because  the  accuracy  of  some  of  the  methods  depends 
upon  the  fineness  of  the  sample.  In  case  a  hacksaw  cannot  be 
used,  obtain  fine  drillings  with  a  small  drill.  A  magnet  should 
always  be  passed  through  the  sample  before  starting  the  analysis. 

(1)  SOLDER 

General. — Solders  usually  consist  of  Sn  and  Pb  with  a 
small  amount  of  Sb  as  impurity. 

Tin  (Gravimetric  Method). — Weigh  accurately  0.5  gram  of 
sample  into  a  250  cc.  beaker,  add  15  cc.  of  HNOs  (2:1),  cover 
immediately  with  a  watch  glass,  and,  when  violent  action  ceases, 
boil  until  no  more  red  fumes  are  given  off.  Place  the  beaker  on 
the  water  bath  and  digest  thirty  minutes.  Dilute  with  30  cc.  of 
hot  water.  Let  the  precipitate  settle  and  filter,  washing  with 
2%  HNOs.  Place  the  filter  paper  and  contents  in  a  weighed  por- 
celain crucible.  Smoke  off  the  paper  and  ignite  fifteen  minutes 
in  the  full  heat  of  a  Tirrill  burner.  Cool  in  a  desiccator  and 
weigh.  This  represents  SnC>2+ 80204,  together  with  a  small 
amount  of  PbO.  Fuse  the  ignited  precipitate  with  a  mixture  of 
finely  powdered  sulfur  and  Na2CO3,  in  the  proportions  of  1  part 
of  precipitate  to  3  parts  each  of  S  and  Na2COs,  in  a  covered  por- 
celain crucible  until  the  odor  of  SO2  has  disappeared.  Cool  and 
dissolve  the  fusion  in  hot  water;  add  an  excess  of  Na2SOs  to  con- 
vert any  polysulfides  to  monosulfides;  filter  and  wash  the  pre- 
cipitate thoroughly. 

This  precipitate  contains  the  Pb.     Dissolve  it  in  dil.  HNOs 
(1  :  3)  and  determine  the  Pb  electrolytically  in  the  usual  way, 


ANALYSIS  OF  METALS  155 

weighing  as  PbO2  on  the  anode.  Calculate  the  weight  thus 
found  to  PbO  and  subtract  from  the  original  weight  of  the  pre- 
cipitate. (Also  calculate  it  to  Pb  and  add  to  the  main  Pb  deter- 
mination as  later  described.)  Also  calculate  the  Sb  (determined  as 
described  later)  to  Sb2O4  and  subtract  this  from  the  original 
precipitate.  The  remainder  is  SnO2.  Calculate  this  to  Sn.- 

CALCULATIONS.—      Sb  X  1.2662  =  Sb2O4. 
Pb02X0.9331  =  PbO. 
PbO2X  0.8643  =  Pb.* 

SnO2X  0.7877  =  Sn. 

Tin  (Alternative  Method). — Weigh  accurately  0.5  gram  of 
sample  into  a  300  cc.  Erlenmeyer  flask  fitted  with  a  1-hole  stopper 
carrying  a  1  mm.  capillary  tube  running  into  a  6-inch  test  tube  as 
shown  in  Fig.  8.  Add  to  the  flask  25  cc.  of  10%  Na2CO3  solution, 
50  cc.  of  hot  water,  50  cc.  of  cone.  HC1  and  1 
drop  of  5%  SbCls  solution.  Fill  the  test  tube 
one-third  full  with  10%  Na2CO3  solution  and 
insert  the  capillary  tube  into  it.  Place  on 
the  water  bath  and  heat  until  all  except  the 
Cu  and  Sb  is  dissolved,  which  requires  about 
fifteen  minutes.  Remove  the  flask  from  the 
water  bath,  fill  the  test  tube  with  10%  Na2C03 

solution  and  cool  under  running  water.     When  FlG<  8- ""  APParatus 

,      j  j  ,      ,1"     «     t    *.  £  i     for  Determination  of 

cool  add  to  the  flask  5  cc.  of  arrowroot  starch  Tin  -n  Wnite  Metais 

solution,  then  25  cc.  of  10%  Na2CO3  solution 
and  titrate  with  0.1  N  iodine,  covering  the  flask  with  a  rubber 
washer  which  fits  over  the  tip  of  the  burette.  The  starch  and 
Na2CC>3  solution  are  best  added  from  a  pipette  by  inserting  its  tip 
between  the  stopper  and  the  neck  of  the  flask,  allowing  as  little 
air  as  possible  to  enter  the  flask  as  it  causes  low  results. 

NOTE. — Standardize  the  iodine  solution  against  0.2500  gram  of  c.  p.  tin, 
following  exactly  the  details  of  this  method.  Divide  0.2500  by  the  number  of 
cc.  of  I  solution  used  for  titration.  The  quotient  is  the  factor  of  the  solution 
in  terms  of  tin. 

Antimony. — Weigh  accurately  1  gram  of  sample  into  a  500  cc. 
Pyrex  Erlenmeyer  flask.  Add  15  cc.  of  cone.  H2SC>4  and  4-5 

*  Empirical  factor. 


156  TECHNICAL  METHODS  OF  ANALYSIS 

grams  of  K2SO4.  Heat  until  the  residue  is  perfectly  white,  but 
do  not  drive  off  all  the  free  H2SO4,  which  makes  the  melt  hard  on 
cooling.  Cool  thoroughly,  add  50  cc.  of  10%  tartaric  acid  solu- 
tion and  10  cc.  of  cone.  HC1.  Heat  until  all  soluble  matter  is 
dissolved,  cool  very  thoroughly,  add  110  cc.  of  water  and  10  cc. 
more  of  cone.  HC1,  cool  again  and  titrate  at  once  with  0. 1  N 
KMnO4.  The  end  point  is  distinct  but  fades  quite  rapidly. 
From  the  known  strength  of  the  KMnCX  solution  calculate  the 
per  cent  of  Sb. 

STANDARDIZATION. — Standardize  the  KMnCU  solution  against 
c.  P.  antimony  and  calculate  the  value  of  the  solution  in  terms  of 
Sb;  then  the  personal  error  in  the  end  point  will  be  the  same  as 
in  the  actual  analysis.  Use  the  following  procedure: 

Weigh  out  exactly  0.1500  gram  of  c.  P.  antimony  and  an 
equal  quantity  of  c.  p.  tin.  Place  in  a  500  cc.  Erlenmeyer  flask, 
add  15  cc.  of  cone.  H2SO4  and  4-5  grams  of  K^SCX.  Heat  until 
the  metals  are  in  solution  or  entirely  decomposed  and  all  separated 
S  is  driven  off.  Do  not  drive  off  enough  SOs  to  cause  the  melt  to 
harden  on  cooling.  Cool,  add  50  cc.  of  10%  tartaric  acid  solution 
and  10  cc.  of  cone.  HC1,  and  heat  until  a  clear  solution  is  obtained. 
Cool  the  solution  to  tap  water  temperature;  then  add  110  cc. 
more  of  water  and  10  cc.  more  of  cone.  HC1.  Cool  again  and 
titrate  at  once  to  a  pink  color  with  KMnC>4  solution. 

0.1500 

CALCULATION. — Sb  factor  = „  ^  r  -  -. 

cc.  of  KMn(J4  used 

Lead. — To  the  filtrate  from  the  gravimetric  Sn  determination 
add  10  cc.  of  cone.  H2SO4,  and  evaporate  until  copious  fumes  of 
SOs  are  evolved.  Cool  thoroughly  and  take  up  with  100  cc.  of 
water;  boil  and  let  stand  until  perfectly  cold  (preferably  over- 
night). Filter  the  PbSC>4  on  a  weighed  ignited  Gooch  crucible 
and  wash  with  5%  H2SO4,  and  then  with  50%  ethyl  alcohol  until 
the  washings  are  free  from  acid.  Do  not  run  alcohol  into  the  main 
filtrate  as  it  will  interfere  with  subsequent  electrolysis  for  Cu. 
It  is  used  merely  for  removing  the  acid  from  the  PbSO4.  Place 
the  Gooch  crucible  inside  of  a  platinum  crucible  and  ignite.  Cool 
in  a  desiccator  and  weigh  as  PbSC>4.  Calculate  to  Pb. 

CALCULATION.— PbSO4  X  0.6833  =  Pb. 

NOTE. — Any  Pb  found  in  purifying  the  tin-antimony  oxides,  as  previously 
described,  must  be  added  to  the  amount  here  found. 


ANALYSIS  OF  METALS  157 

Copper. — Dilute  the  filtrate  from  the  Pb  determination  to 
approximately  200  cc.  and  electrolyze  for  copper  in  a  250  cc. 
beaker,  as  described  under  Brass  and  Bronze,  page  145. 

Zinc. — To  the  solution  from  which  Cu  has  been  removed, 
add  75  cc.  of  30%  NaOH  solution  and  electrolyze  as  described 
under  Brass  and  Bronze,  page  146. 

(2)  BABBITT  METALS 

General. — Babbitts  may  be  divided  into  two  general  classes: 

(A)  Those  in  which  Sn  predominates. 

(B)  Those  containing  a  high  percentage  of  Pb. 

(A)  High-Tin  Babbitts 

Tin. — Weigh  out  accurately  0.5  gram  of  sample,  transfer  to  a 
250  cc.  beaker  and  determine  Sn  and  Sb  as  oxides,  as  described 
above  under  Solder. 

Antimony. — Using  a  1  gram  sample,  determine  the  Sb  by  the 
method  previously  described  for  Sb  in  Solder. 

Copper  and  Lead. — Dilute  the  filtrate  from  the  Sn  determina- 
tion to  about  200  cc.  and  add  cone.  HNOs  until  the  solution  con- 
tains approximately  10%.  Electrolyze  as  described  under  Copper 
in  Brass  and  Bronze,  page  145.  The  Pb  will  be  deposited  at  the 
same  time  on  the  anode  as  Pb02.  Calculate  its  weight  to 
metallic  Pb. 

CALCULATION.— PbO2  X  0.8643  =  Pb.  * 

NOTE. — To  the  Cu  and  Pb  thus  determined  must  be  added  the  Cu  and  Pb 
recovered  as  impurities  from  the  SnC>2  by  the  procedure  previously  described 
in  the  method  for  Solder.  At  the  same  time  that  the  Pb  from  the  purification 
of  the  SnO2  is  deposited  on  the  anode,  the  Cu  is  deposited  on  the  cathode. 

Zinc. — To  the  liquid  from  which  the  Cu  and  Pb  have  been 
removed  add  2-3  cc.  of  cone.  H2S04,  and  evaporate  to  copious 
fumes  of  SOs.  Cool,  add  50  cc.  of  30%  NaOH  solution,  and  elec- 
trolyze for  Zn  as  described  under  Brass  and  Bronze,  page  146. 

Copper  and  Lead  (Alternative  Method). — Treat  1  gram  of 
finely  divided  sample  in  a  250  cc.  covered  beaker  with  10  cc.  of 
aqua  regia.f  Add  a  little  KClOa  and  heat;  then  add  a  little  tar- 

*  Empirical  factor. 

1  Aqua  regia.    1  part  cone.  HNO3,  3  parts  cone.  HC1. 


158  TECHNICAL  METHODS  OF  ANALYSIS 

taric  acid  and  dilute  with  water.  Make  slightly  alkaline  with 
NaOH.  If  a  precipitate  forms,  make  acid  again  with  HC1,  add 
more  tartaric  acid  and  then  make  alkaline  with  NaOH.  When 
a  clear  solution  is  obtained,  add  25  cc.  of  saturated  Na2S  solution. 
Digest  on  the  steam  bath  for  thirty  minutes,  stirring  frequently. 
Let  the  precipitate  of  PbS  and  CuS  settle;  filter  on  an  asbestos 
mat  in  a  loose  bottom  Gooch  crucible  and  wash  with  2%  Na2S  solu- 
tion. Transfer  the  asbestos  mat  and  crucible  to  a  small  beaker  and 
dissolve  the  sulfides  in  20  cc.  of  cone.  HNOs.  Dilute  to  200  cc. 
and  determine  the  Pb  and  Cu  by  simultaneous  electrolysis, 

(B)  High-Lead  Babbitts 

Tin. — Dissolve  exactly  1  gram  of  sample  in  a  250  cc.  beaker 
with  15  cc.  of  HNOs  (2  :  1).  If  the  material  is  low  in  Sn,  add 
sufficient  pure  Sn,  accurately  weighed,  so  that  the  ratio  Sn  :  Sb 
is  at  least  3:1,  otherwise  the  Sb  will  not  be  completely  precip- 
itated. Complete  the  determination  of  Sn  as  previously  described 
under  Solder,  deducting  the  equivalent  of  pure  Sn  added. 

Antimony. — Determine  Sb  in  the  same  manner  as  described 
under  Solder,  page  155. 

Lead. — Determine  Pb  as  described  under  Solder,  page  156. 

Copper. — If  Cu  is  present,  electrolyze  the  solution  as  pre- 
viously described  for  Cu  in  Solder,  page  157. 

Zinc. — If  Zn  is  present,  treat  the  liquid  from  the  Pb  deter- 
mination and  electrolyze  it  as  described  under  Zinc  in  High-Tin 
Babbitts,  above, 

(3)  TYPE  METALS 
(LINOTYPE,  STEREOTYPE,  MONOTYPE,  ETC.) 

Tin. — Heat  1  gram  of  the  sample,  accurately  weighed,  in  a 
300  cc.  Erlenmeyer  flask,  with  50  cc.  of  cone.  HC1  on  the  steam 
bath  until  all  action  ceases.  While  the  solution  is  still  hot  add 
2  or  3  small  crystals  of  KClOa  at  a  time  and  shake  until  a  clear 
solution  is  obtained.  Avoid  an  excess  of  KClOs.  Now  add  50  cc. 
of  cone.  HC1,  100  cc.  of  hot  H20,  2  grams  of  steel  drillings  (see 
note  1)  and  25  cc.  of  10%  Na2COs  solution,  in  the  order  given. 


ANALYSIS  OF  METALS  159 

Quickly  insert  the  stopper  carrying  the  bent  capillary  tube  and 
test  tube,  as  shown  on  page  155.  The  test  tube  must  be  one-third 
full  of  10%  Na2COs  solution.  Place  on  the  steam  bath  and  heat 
until  the  steel  is  entirely  dissolved  (see  note  2).  Fill  the  test  tube 
with  10%  Na2COs  solution  and  cool  the  flask  to  tap  water  tempera- 
ture. Add  to  the  flask  5  cc.  of  arrowroot  starch,  then  25  cc.  oT 
10%  Na2CC>3  solution,  from  pipettes,  and  complete  the  deter- 
mination as  described  in  the  alternative  method  for  Tin  in  Solder 
(page  155),  being  careful  to  exclude  air  as  completely  as  possible. 

NOTES. — (1)  Plain  carbon  steel  drillings,  containing  0.35-0.60%  carbon, 
give  the  best  results.  They  must  not  be  too  fine. 

(2)  All  yellow  color  due  to  chlorine  should  be  destroyed.     If  not,  the  analy- 
sis must  be  repeated,  as  too  much  KC1O3  has  been  added  and  the  results  will 
be  low. 

(3)  Some  trouble  may  be  experienced  at  first  in  seeing  the  end  point  on 
account  of  suspended  carbon.     This  can  best  be  seen  by  looking  down  through 
the  bottom  of  the  flask  where  light  shows  through  the  solution.     As  soon  as 
the  blue  end  point  is  reached,  the  solution  becomes  opaque  at  this  point;  and 
as  soon  as  the  carbon  settles,  the  deep  blue  color  can  be  seen  distinctly. 

(4)  A  blank  determination  should  be  made  by  each  operator,  testing  0.1500 
gram  of  pure  Sb  (but  no  Sn)  and  proceeding  exactly  as  described  above.     This 
blank  titration  should  be  subtracted  from  the  total  titration. 

(5)  The  iodine  solution  used  should  be  standardized  against  pure  Sn 
exactly  as  described  under  the  determination  of  Sn  in  Solder,  page  155. 

Tin  (Alternative  Method). — Weigh  accurately  1  gram  of  sam- 
ple, together  with  sufficient  c.  P.  tin  so  that  the  ratio  Sn  :  Sb  is  at 
least  3:1,  into  a  250  cc.  beaker.  Determine  the  Sn  gravimet- 
rically  as  above  described  under  Solder,  page  154.  It  will  be 
necessary  to  purify  the  precipitate  as  there  described. 

NOTE. — The  amount  of  c.  P.  tin  added  should  be  calculated  to  SnO2 
and,  together  with  the  impurities  and  Sb2O4,  deducted  from  the  total  weight 
of  the  precipitate. 

CALCULATION. — Sn  X 1 .2696  =  SnC>2 . 

Antimony. — Determine  Sb  on  0.5  gram  of  the  sample  exactly 
as  described  under  Solder,  page  155. 

Lead. — Treat  0.5  gram  of  the  finely  divided  sample  in  a  250 
cc.  Erlenmeyer  flask  with  4-7  grams  of  tartaric  acid  (depending 
upon  the  amount  of  Sn  and  Sb  present),  15  cc.  of  water  and  4  cc. 
of  cone.  HNOs,  and  heat  on  the  steam  bath  until  a  clear  solution 
is  obtained.  Add  cautiously  and  with  constant  stirring  4  cc.  of 


160  TECHNICAL  METHODS  OF  ANALYSIS 

cone.  H2S04,  dilute  with  50  cc.  of  distilled  water  and  let  cool  until 
the  precipitate  settles  completely  (at  least  one  hour).  All  Pb 
will  be  precipitated  as  PbSO4.  Filter  on  a  Gooch  crucible,  wash 
with  5%  H2S04  and  then  with  50%  ethyl  alcohol  until  the  wash- 
ings are  free  from  acid.  Set  the  crucible  inside  a  platinum 
crucible,  ignite  and  weigh  as  PbS04,  as  described  under  Lead  in 
Solder,  page  156, 


(4)  ALUMINUM  ALLOYS 

General. — In  accordance  with  common  practice  with  high  Al 
alloys,  the  amounts  of  all  other  elements  present  are  determined 
and  the  Al  taken  by  difference.  This  is  on  account  of  the  diffi- 
culties that  are  usually  encountered  in  determining  Al  where  it  is 
present  in  such  large  amounts.  All  the  determinations  should 
be  made  in  duplicate.  It  is  always  advisable  to  make  a  quali- 
tative analysis  before  attempting  quantitative  work. 

Silicon. — Dissolve  1  gram,  accurately  weighed,  of  well-mixed 
drillings  in  35  cc.  of  acid  mixture  (see  below),  using  a  porcelain 
dish  covered  with  a  watch  glass.  When  the  drillings  are  com- 
pletely dissolved,  evaporate  the  solution  to  dryness  and  bake  on 
the  hot  plate  for  at  least  one-half  hour.  This  insures  complete 
dehydration  of  SiC>2.  Take  up  the  residue  with  HC1  (1  : 4), 
filter,  and  wash  with  hot  water.  Ignite  and  weigh  as  Si02.  Cal- 
culate to  Si  by  multiplying  by  0.4693. 

Acid  Mixture. — Pour  150  cc.  of  cone.  H2S04  into  450  cc.  of 
water.  Cool  and  add  100  cc.  of  cone.  HNOa  and  then  300  cc.  of 
cone.  HC1. 

Aluminum. — If  for  any  reason  it  is  desired  to  make  a  direct 
determination  of  aluminum,  dilute  the  filtrate  from  the  Si  deter- 
mination to  500  cc.  in  a  volumetric  flask,  and,  after  thoroughly 
mixing,  take  a  100  cc.  aliquot  for  analysis.  Dilute  the  solution  to 
approximately  300  cc.,  add  a  pinch  of  tannic  acid  and  a  slight  excess 
of  NttiOH.  Boil  until  the  odor  of  NH3  is  nearly  gone.  Filter 
and  wash  with  hot  water.  Dissolve  the  precipitate  in  hot  HC1 
(1  :  1),  add  a  pinch  of  tannic  acid,  reprecipitate  exactly  as  pre- 
viously, and  wash  with  hot  water.  Dry  the  paper  and  residue, 
ignite  with  a  blast  lamp  in  a  platinum  crucible  to  constant  weight 


ANALYSIS  OF  METALS  161 

and  weigh  as  Al203+Fe203.  Subtract  the  Fe20s  present  (as  later 
determined)  and  calculate  the  remainder  to  Al. 

CALCULATION.— A1203  X  0.5303  =  Al. 

Manganese. — Dissolve  1  gram  of  finely  divided  sample  in  50  cc. 
of  HNOs  (1  :  3)  in  a  200  cc.  Erlenmeyer  flask.  Since  Al  dissolves 
very  slowly  in  HNOs,  this  may  require  some  time.  When  entirely 
in  solution,  cool  to  about  15°  C.,  add  0.5  gram  of  sodium  bismuth- 
ate  and  agitate  for  a  few  minutes.  Add  50  cc.  of  3%  HNOs,  and 
filter  through  an  extra-porous  alundum  thimble.  Wash  with 
50-100  cc.  of  the  same  acid  and  finally  with  water.  Do  not 
let  the  solution  come  in  contact  with  rubber  connections.  Titrate 
the  filtrate  in  the  flask  with  standard  sodium  arsenite  solution 
(see  note  1)  as  described  under  Manganese  in  Steel,  page  111. 

NOTES. — (I)  The  total  amount  of  Mn  titrated  in  this  way  should  not  be 
over  0.0125  gram.  If,  therefore,  the  material  contains  over  1.25%  of  Mn,  use 
a  0.5  gram  sample. 

(2)  Arsenite  Solution. — The  arsenite  solution  which  is  used  for  titrating 
Mn  in  Steel  will  be  suitable  (see  page  111). 

(3)  In  case  the  sample  is  not  fine,  it  may  be  necessary  to  use  a  small  amount 
of  HC1  to  effect  solution,  and  subsequently  drive  this  off  by  evaporating  to  a 
small  volume  with  successive  portions  of  cone.  HNO3,  before  proceeding  with 
the  method  above  described. 

Tin. — Weigh  accurately  a  1  gram  sample,  together  with  approx- 
imately 5  grams  of  NaOH,  into  a  beaker  and  add  just  enough 
water  to  cover  the  sample.  When  violent  action  has  ceased, 
dilute  to  about  100  cc.  and  boil  for  four  or  five  minutes.  Cool, 
filter,  and  wash  the  residue  with  hot  water  until  free  from  alkali. 
The  Al  and  practically  all  the  Zn  are  dissolved,  while  other  metals 
remain  unaffected.  Save  the  filtrate  for  subsequent  determina- 
tion of  Zn. 

Wash  the  bulk  of  the  residue  from  the  NaOH  treatment  into  a 
beaker.  Ash  the  filter  and  add  it  to  the  beaker.  Add  20  cc.  of 
cone.  HNOs  and  evaporate  to  approximately  10  cc.  Dilute  to 
50  cc.  with  water.  Filter,  wash,  ignite  in  a  porcelain  dish,  and 
weigh  as  SnC>2.  Calculate  to  Sn. 

CALCULATION.— Sn02  X  0.7877  =  Sn. 

Copper  and  Lead. — Bring  the  volume  of  the  filtrate  to  200  cc. 
and  add  10  cc.  of  cone.  HNOs.  Electrolyze  for  Cu  and  Pb  as 
described  under  Brass  and  Bronze,  page  145. 


162  TECHNICAL  METHODS  OF  ANALYSIS 

Iron. — Make  the  solution  from  the  Cu  and  Pb  determination 
alkaline  with  NHiOH,  and  boil.  Filter  off  the  precipitate  of 
Fe(OH)3  and  wash  with  hot  water.  Dissolve  this  precipitate 
from  the  filter  by  pouring  hot  dil.  H2SO±  upon  it,  catching  the 
solution  in  a  beaker.  Dilute  this  solution  until  the  H^SC^  present 
is  approximately  5%.  Heat  nearly  to  boiling  and  pass  through 
a  Jones  reductor.  Cool  and  titrate  with  0.1  N  KMn04  solution. 

CALCULATION.— 1.  cc.  0.1  N  KMn04  =  0.005584  gram  Fe. 

=  0.007984  gram  Fe203. 

NOTE. — A  blank  should  be  run  on  the  reductor  (using  the  same  amounts  of 
acid  and  of  solution)  and  subtracted  from  the  titration  of  the  sample.  (See 
page  148.) 

Nickel. — Heat  to  boiling  the  above  filtrate  from  the  Fe(OH)s 
precipitate  and  add  a  1%  solution  of  dimethylglyoxime, 
(CHs)2C2(NOH)2,  in  ethyl  alcohol,  until  the  amount  of  reagent  is 
about  5  times  that  of  the  Ni  supposed  to  be  present.  A  large  excess 
does  no  harm  but  it  is  unnecessary  and  the  reagent  is  very  expen- 
sive. Let  the  solution  stand  on  the  water  bath  for  thirty  minutes 
and  filter  while  still  hot  through  a  weighed  porcelain  Gooch 
crucible.  Wash  with  hot  water  and  dry  to  constant  weight  at 
110-120°  C.  Weigh  as  nickel  glyoxime,  CgHuN^Ni,  and 
calculate  to  Ni. 

CALCULATION.— C8Hi4N404NiX  0.2031  =  Ni. 

Zinc. — Dilute  the  filtrate  from  the  original  NaOH  treatment 
in  the  tin  determination  to  200  cc.  and  determine  the  Zn  by  elec- 
trolysis as  described  in  the  method  for  Brass  and  Bronze,  page  146. 
Discard  the  solution  after  the  Zn  is  removed.  Some  Zn  may  remain 
insoluble  in  NaOH  and  should  be  recovered  as  follows:  Boil  the 
filtrate  from  the  Ni  determination  until  the  free  NHs  is  expelled. 
Acidify  with  dil.  H2SO4,  adding  the  equivalent  of  2-3  cc.  of  cone. 
H2SO4  in  excess.  Transfer  to  a  500  cc.  Pyrex  Erlenmeyer  flask 
and  evaporate  to  80s  fumes.  If  the  solution  is  dark  colored, 
add  a  few  cc.  of  cone.  HNOs  and  again  evaporate  to  SOs  fumes. 
Take  up  with  water,  cool,  add  50  cc.  of  30%  NaOH  solution, 
dilute  to  200  cc.  in  a  250  cc.  beaker  and  electrolyze  for  Zn  as 
previously  described.  Add  the  Zn  obtained  here  to  that  obtained 
by  electrolysis  of  the  filtrate  from  the  original  NaOH  treatment. 

Magnesium. — After  any  Zn  present  has  been  removed  by  elec- 
trolysis, acidify  with  cone.  HC1,  adding  about  10  cc.  in  excess. 


ANALYSIS  OF  METALS  163 

Dilute  to  about  300  cc.,  cool  to  tap  water  temperature  and  add  30 
cc.  of  a  saturated  solution  of  microcosmic  salt,  NEUNaHPO*  -4H20. 
Add  NEUOH  drop  by  drop,  stirring  vigorously  to  make  the  pre- 
cipitate crystalline.  Then  add  an  excess  of  cone.  NHiOH,  approx- 
imately 10%  of  the  volume  of  the  whole  solution.  Let  stand  over- 
night, filter  through  a  weighed  Gooch  crucible,  and  wash  with  cold 
water  containing  5%  of  cone.  NHiOH  and  5%  of  NILiNOs. 
Ignite  until  completely  white.  Weigh  as  Mg2?2O7  and  calculate 
to  Mg. 

CALCULATION.— Mg2P2O7X  0.2184  =  Mg. 

REFERENCES. — Price  and  Meade:  "Technical  Analysis  of  Brass  and 
Non-Ferrous  Alloys;"  E.  Blough:  "Analysis  of  Aluminum  and  Its  Com- 
mercial Alloys." 

MERCURY  IN  ZINC  AMALGAM 

General. — So-called  Battery  Zincs  are  often  made  of  zinc  amal- 
gam containing  1-3%  of  mercury.  The  following  method  is  a 
convenient  one  for  the  determination  of  the  amount  of  Hg  and 
gives  accurate  results. 

Determination. — Dissolve  4-5  grams  of  finely  divided  alloy  in 
about  75  cc.  of  HC1  (1:1)  and  boil  two  to  three  hours.  This  dis- 
solves Zn,  whereas  any  Hg  and  Pb  which  are  present  will  be 
separated  as  metal. 

Decant  off  the  solution,  wash  the  residue  several  times  with 
hot  water  and  transfer  to  a  porcelain  crucible.  Place  in  the  oven 
and  dry  at  100°  C.  Cool  in  a  desiccator  and  weigh.  Then 
ignite  at  a  red  heat  and  again  cool  in  a  desiccator  and  weigh. 
The  loss,  represented  by  the  difference  in  weight,  is  mercury. 

NOTE. — The  ignition  should  be  conducted  under  a  hood  and  care  taken  not 
to  breathe  the  mercury  fumes,  which  are  poisonous. 

REFERENCE. — This  method  has  been  used  for  some  time  at  the  laboratory 
of  the  N.  Y.,  N.  H.  &  H.  Railroad. 

TESTING  OF  GALVANIZING  OR  SHERADIZING  ON  IRON  AND  STEEL 

General. — There  are  two  methods  of  applying  a  protective 
zinc  coating  to  iron  and  steel. 

Galvanizing  deposits  a  layer  of  metallic  zinc  on  the  surface  and 
gives  a  bright,  smooth,  shiny  surface  generally  showing  the  char- 
acteristic crystalline  structure  of  Zn. 


164  TECHNICAL  METHODS  OF  ANALYSIS 

Sheradizing  forms  a  dull  gray  (nearly  slate  colored)  coating 
generally  more  or  less  rough.  This  coating  is  not  metallic  Zn 
as  in  the  case  of  galvanizing  but  is  a  mixture  of  metallic  Zn  and  a 
Zn-Fe  alloy. 

The  Preece  test,  described  herewith,  was  originally  designed 
for  galvanized  articles  and  particular  care  must  be  employed, 
in  applying  it  to  sheradized  articles,  to  brush  the  specimen  vigor- 
ously with  a  wire  brush  after  each  dip  and  not  to  be  deceived  by  an 
apparent  plating  of  copper  which  can  be  removed  by  further  dips 
and  scrubbing. 

Cleaning. — The  samples  shall  be  cleaned  before  testing,  first 
with  CCU,  benzine  or  turpentine,  and  cotton  waste  (not  with 
a  brush),*  and  then  thoroughly  rinsed  in  clean  water  and  wiped 
dry  with  clean  cotton  waste.  The  samples  must  be  clean  and  dry 
before  each  immersion  in  the  test  solution. 

Solution. — The  standard  solution  of  copper  sulfate  shall  con- 
sist of  commercial  copper  sulfate  crystals  dissolved  in  cold  water, 
in  the  proportion  of  about  36  parts  by  weight  of  crystals  to  100 
parts  of  water.  The  solution  shall  be  neutralized  by  the  addition 
of  an  excess  of  chemically  pure  CuO.  The  presence  of  an  excess 
of  CuO  will  be  shown  by  the  sediment  of  this  reagent  at  the  bot- 
tom of  the  containing  vessel. 

The  neutralized  solution  shall  be  filtered  before  use  by  passing 
through  filter  paper.  The  filtered  solution  shall  have  a  sp.  gr. 
of  1.186  at  65°  F.f  (reading  the  scale  at  the  level  of  the  solution) 
at  the  beginning  of  each  test.  In  case  the  filtered  solution  is  high 
in  sp.  gr.,  clean  water  shall  be  added  to  reduce  the  sp.  gr.  to  1.186 
at  65°  F.  In  case  the  filtered  solution  is  low  in  sp.  gr.,  a  filtered 
solution  of  a  higher  sp.  gr.  shall  be  added  to  make  the  sp.  gr.  1.186 
at  65°  F. 

As  soon  as  the  stronger  solution  is  taken  from  the  vessel  con- 
taining the  unfiltered  neutralized  stock  solution,  additional  crystals 
and  water  must  be  added  to  the  stock  solution.  An  excess  of  CuO 
shall  always  be  kept  in  the  unfiltered  stock  solution. 

Quantity  of  Solution. — Wire  samples  shall  be  tested  in  a  glass 
jar  of  at  least  2  inches  inside  diameter.  The  jar  without  the  wire 
samples  shall  be  filled  with  standard  solution  to  a  depth  of  at  least 

*  Except  for  sheradized  articles. 

t  This  is  equivalent  to  a  reading  of  22.7°  on  a  Baiiine*  hydrometer  at  65°  F. 


ANALYSIS  OF  METALS  165 

4  inches.  Hardware  samples  shall  be  tested  in  a  glass  or  earthen- 
ware jar  containing  at  least  0.5  pint  of  standard  solution  for  each 
hardware  sample.  Solutions  shall  not  be  used  for  more  than  one 
series  of  4  immersions. 

Samples. — Not  more  than  7  wires  shall  be  simultaneously 
immersed,  and  not  more  than  1  sample  of  galvanized  material 
other  than  wire  shall  be  immersed,  in  the  specific  quantity  of 
solution.  The  samples  shall  not  be  grouped  or  twisted  together, 
but  shall  be  well  separated  so  as  to  permit  the  action  of  the.  solution 
to  be  uniform  upon  all  immersed  portions  of  the  samples. 

Test. — The  clean  and  dry  samples  shall  be  immersed  in  the 
required  quantity  of  standard  solution  in  accordance  with  the 
following  cycle  of  immersions.  The  temperature  of  the  solution 
shall  be  maintained  between  62-68°  F.  at  all  times  during  the 
following  test. 

First. — Immerse  for  one  minute,  wash  and  wipe  dry.* 
Second — Immerse  for  one  minute,  wash  and  wipe  dry. 
Third. — Immerse  for  one  minute,  wash  and  wipe  dry. 
Fourth. — Immerse  for  one  minute,  wash  and  wipe  dry. 

After  each  immersion  the  samples  shall  be  immediately  washed 
in  clean  water  having  a  temperature  between  62-68°  F.,  and 
wiped  dry  with  cotton  waste.* 

In  testing  wire  of  No.  13  B.  W.  G.  and  smaller  sizes,  the  time 
of  the  fourth  dip  shall  be  reduced  to  one-half  minute. 

Interpretation. — If  the  samples  as  tested  above  show  bright, 
firmly  adhering  metallic  copper  deposits,  they  are  considered  as 
having  failed  to  pass  the  test. 

In  the  case  of  sheradized  articles  there  will  be  a  copper  deposit 
formed  on  each  dip,  due  to  the  Fe-Zn  alloy.  This  deposit,  however, 
is  not  firmly  adhering  nor  of  the  typical  bright  color  of  the  Cu 
plate  which  indicates  failure.  It  can  be  removed  by  vigorous 
scrubbing  with  a  wire  brush  under  running  water  and  care  must  be 
taken  not  to  reject  sheradized  articles  unless  they  show  a  firmly 
adhering  Cu  deposit  which  is  bright  colored  and  cannot  be  removed 
by  wire  brushing  or  by  further  dipping  and  brushing. 

*  In  the  case  of  sheradized  materials  the  specimens  must  be  quickly 
removed  to  running  water  after  each  dip  and  brushed  vigorously  with  a  wire 
brush  while  in  the  running  water. 


166  TECHNICAL  METHODS  OF  ANALYSIS 

Copper  deposits  on  zinc  or  within  1  inch  of  the  cut  end  may  be 
disregarded. 

If  one  wire  in  a  group  of  7  wires  immersed  together  shows  a 
Cu  deposit,  or  if  there  is  reasonable  doubt  as  to  the  presence  of 
the  Cu  deposit,  two  check  tests  should  be  made  upon  the  7  wires 
and  the  report  based  on  the  majority  of  the  sets  of  tests. 

In  case  the  article  has  a  cut  screw  the  thread  shall  stand  one 
one-minute  immersion;  the  rest  of  the  article  shall  withstand  the 
specified  4  immersions.  The  threads  of  nuts  are  not  required  to 
stand  the  galvanizing  test. 

REFERENCE.— Amer.  Tel.  &  Tel.  Co.  Specification  3110,  Feb.  3,  1908. 

TINNING  TEST  FOR  TINNED  IRON  AND  STEEL 

Method  of  Am.  Elect.  Railway  Engineering  Assoc. 

(a)  Preparation  of  Samples. — Samples  of  the  wire  or  other 
material  to  be  tested  shall  be  thoroughly  cleaned  with  alcohol. 

'(6)  Tinning  Test.— Immerse  in  HC1  (sp.  gr.  1.088  at  15.5°  C.) 
for  exactly  one  minute.  Rinse  in  pure  water  and  immerse  in  an 
aqueous  solution  of  sodium  sulfide  (sp.  gr.  1.142,  or  28°  Baume)  for 
exactly  thirty  seconds.  Again  wash  in  pure  water  and  repeat  the 
operation  three  times.  At  the  end  of  the  fourth  immersion  in 
Na2$,  the  wire  shall  show  no  sign  of  blackening. 

(c)  Sodium  Sulfide  Solution. — The  Na2$  solution  shall  contain 
an  excess  of  sulfur  and  shall  have  sufficient  strength  to  thoroughly 
blacken  a  piece  of  untinned  copper  wire  in  five  seconds.  Each 
new  solution  made  up  shall  be  tested  for  strength  with  a  piece  of 
untinned  copper  wire. 

Method  of  American  Tel.  and  Tel.  Co. — Immerse  the  samples 
of  wire  or  other  material  to  be  tested  in  a  current  of  pure  H^S 
gas,  saturated  with  water  vapor,  at  a  temperature  of  not  less  than 
24°  C.  nor  more  than  26°  C.,  for  four  hours.  At  the  end  of  this 
time  the  samples  should  show  no  signs  of  blackening. 


CHAPTER  V 
ANALYSIS  OF  FUELS 

COAL  SAMPLING 

General. — The  main  object  in  taking  a  sample  of  coal  is  to 
secure  a  small  portion  of  the  coal  which  represents  as  nearly  as 
possible  the  entire  shipment.  It  is  extremely  important  that  the 
sample  be  properly  taken,  as  in  many  cases  it  is  entirely  impos- 
sible to  obtain  another  sample.  Wherever  possible  collect  the 
sample  while  the  coal  is  being  loaded  into  or  unloaded  from  cars, 
boats,  trucks  or  other  conveyor.  When  coal  is  being  crushed  as 
received  it  is  often  advantageous  to  take  the  sample  as  it  comes 
from  the  crusher.  Samples  taken  only  from  the  surface  of  piles 
or  bins  are  generally  unreliable. 

Gross  Sample. — In  collecting  the  sample  use  a  shovel  or  other 
tool  which  will  take  equal  portions.  For  slack  coal  or  small  sizes 
of  anthracite  each  shovelful  may  be  as  small  as  5-10  Ibs.,  but 
for  lump  coal  or  run-of-mine  the  amount  of  each  shovelful  should 
be  10-30  Ibs.  The  total  sample  obtained  in  this  way  is  called 
the  gross  sample.  Wherever  possible  the  gross  sample  should  not 
be  less  than  1000  Ibs.,  except  in  the  case  of  slack  coal  and  small 
sizes  of  anthracite  (not  greater  than  f  inch),  where  500  Ibs.  are 
sufficient.  If  the  coal  contains  an  unusual  amount  of  slate  or 
other  impurities  and  if  the  pieces  of  such  impurities  are  very  large, 
collect  a  gross  sample  of  1500  Ibs.  or  more.  The  gross  sample 
should  contain  the  same  proportions  of  lump,  fine,  and  impurities 
as  in  the  coal  sampled.  The  gross  sample  should  preferably  be 
collected  in  a  large  receptacle  with  cover  attached. 

A  gross  sample  should  be  taken  for  each  1000  tons  or  less 
delivered,  unless  otherwise  specified. 

When  necessary  to  sample  from  loaded  car  or  in  bins  or  piles, 
the  shovelfuls  should  be  taken  by  a  systematic  plan  in  sufficient 

167 


168 


TECHNICAL  METHODS  OF  ANALYSIS 


First  stage  in  the 
preparation  of 
I.OOO-pound 

sample 


Crush  1,000-pound  sample  on 
hard,  clean  surface  to  I"  size 


I.OOO-pound  sample  crushed 
to  1"  and  coned 


Second  stage. 


Mix  by  forming  long  pile. 
A—  spreading  out  first  shovelful. 
B—  long  pile  completed 


.._.. 

Crush  500-pound  sample  500  pounds  Crushed  to&"  and  coned  Mix  by  forming  long  pile. 


Third  stage. 


Crush  250-pound  sample 
(fig.  10.  4)  to  !^" 


250-pounds  crush'ed  to  j£"  »n^  c°n*&  Mix  by  forming  new  cone 


Fourth  stage. 


Crush  125-pound  sample  (fig.  16:  A,  A)  Mix  by  rolling  on  blanket 

on  blanket  to%"  size 


Form  coie  after  mixing 


Fifth  stag*. 


Crush  60-pound  sample  (fig.  22:  A,  A)  Mix  by  rolling-on  blanket 

to  !4"  size 


Form  cone  after  mixing 


Sixth  stage. 


sg? EfEir_L_irr" 

^fe 


29 


Crush  30-pound  sample  (fig.  26:  A,  A)  Mix  by  rolling  on  blanket 

or  4-mesh  size 


Form  cone  after  mixing 


FIG.  9. — Method  of  Preparing  a 


ANALYSIS  OF  FUELS 


169 


..5 


Halving  by  alternate  shovel  method. 
Shovelfuls  1, 3, 5,  etc.,  reserved  as  5,  A; 
2, 4, 6,  etc..  rejected  as  5.  B 


Long  pile  divided  into  two  parts; 
A— reserve;  B— reject 


Shovelful 


_  by  alternate  shovel  method, 
uls  1,3, 5,  etc..  reserved  asKX.4; 
2, 4,  6,  etc.,  rejected  as  10,  B 


NOTE 

SELECT  A  HARD,  CLEAN 
SURFACE,  FREE  OF  CRACKS 
AND  PROTECTED  FROM 
RAIN,  SNOW,  WIND,  AND 
BEATING  SUN.  DO  NOT  LET 
CINDERS,  SAND,  CHIRPINGS 
FROM  FLOOR,  OR  ANY 
OTHER  FOREIGN  MATTER 
GET  INTO  THE  SAMPLE. 
PROTECT  SAMPLE  FROM 
LOSS  OR  GAIN  IN  MOISTURE 


Long  pile  divided  into  two  parts; 
A  —  reserve;  B— reject 


Retain  opposite  quarters  A,  A 
Reject  quarters  B,  B 


Retain  opposite  quarters  A,  A. 
Reject  quarters  B,  B 


Quarter  after  flattening  cone    •  Simple  divided  into  quarters 


Retain  opposite  quarters  A,  A. 
Reject  quarters  B,  B 


Quarter  after  flattening  i 


Sample  divided  into  quarters 


Fill  two  5-pound  sample  containers  from 
A,  A,  0/W  for  laboratory,  one  for  reserve 


Sample  of  Coal  by  Hand. 


170  TECHNICAL  METHODS  OF  ANALYSIS 

number  to  make  the  proper  gross  sample  and  from  as  nearly  all 
parts  of  the  pile  as  possible,  discarding  the  outer  surface  and 
securing  as  nearly  as  possible  the  same  amount  from  the  top,  mid- 
dle and  bottom  of  the  coal. 

Laboratory  Sample. — Having  secured  the  gross  sample  (pro- 
tected from  the  weather  to  avoid  loss  or  gain  in  moisture),  reduce 
it  down  to  a  smaller  sample  as  follows  (see  Fig.  9) : 

Break  down  large  lumps  of  coal  and  impurities  on  a  clean,  hard, 
dry  floor  with  a  suitable  maul  or  sledge  until,  as  judged  by  the  eye, 
there  are  no  pieces  larger  than  specified.  (See  table.)  Then 
thoroughly  mix  by  shoveling  over  and  over  and  form  in  a  conical 
pile.  Reduce  this  down  by  the  alternate  shovel  method  as  follows : 
Take  a  shovelful  from  the  conical  pile  and  spread  it  out  in  a 
straight  line  having  a  width  equal  to  the  width  of  the  shovel  and 
a  length  of  5-10  feet.  Then  spread  the  next  shovelful  in 
the  opposite  direction  over  the  top  of  the  first.  Continue  this, 
occasionally  flattening  the  pile,  until  all  the  coal  has  been  formed 
into  one  long  narrow  pile.  Starting  at  one  end,  on  the  side,  take 
one  shovelful  from  the  bottom  and  set  it  aside.  Then  advance 
along  the  side  of  the  pile  a  distance  equal  to  the  width  of4  the 
shovel,  take  a  second  shovelful  and  set  it  aside  in  a  second  pile. 
Again  advance  in  the  same  direction  one  shovel  width,  take  a  third 
shovelful  and  add  to  the  first.  Take  the  fourth  shovelful  in  the 
same  manner  and  add  it  to  the  second.  Proceed  in  this  way, 
putting  even  shovelfuls  in  one  pile  and  odd  in  another.  Con- 
tinue to  advance  in  the  same  direction  around  the  original  pile, 
so  that  its  size  will  be  gradually  reduced  in  a  uniform  manner. 
Finally  there  will  be  two  piles  containing  approximately  the  same 
amount  of  coal.  Discard  one  of  these.  Spread  out  the  other  and 
crush  down  to  the  size  indicated  in  the  table.  Then  form  in  a 
conical  pile,  followed  by  a  long  narrow  pile,  and  again  reduce  by 
the  alternate  shovel  method. 

After  the  gross  sample  has  been  reduced  by  the  above  method 
to  approximately  250  Ibs.,  further  reduce  it  in  quantity  by  the 
quartering  method.  Before  each  quartering  crush  the  sample  to 
the  prescribed  fineness.  For  quartering,  form  into  a  conical 
pile,  and  flatten  out  the  cone.  Divide  with  a  shovel  or  board  into 
4  equal  segments  and  discard  2  opposite  quarters.  Mix  the  2 
remaining  quarters,  crush  down  to  proper  size,  mix,  reform  into 


ANALYSIS  OF  FUELS  171 

a  conical  pile  and  quarter  as  before.  Continue  the  process  until 
no  lumps  are  greater  than  3^  inch  (or  4-mesh  screen  size)  and 
the  final  sample  amounts  to  about  1-2  quarts. 

TABLE  SHOWING  REQUIRED  FINENESS  FOR  GIVEN  WEIGHT  OF  SAMPLE 

Weight  of  Sample  Largest  Size  Allowable 

1,000  Ibs.  or  over 1  inch 

500  Ibs !  inch 

250  Ibs \  inch 

125  Ibs f  inch 

60  Ibs i  inch 

30  Ibs.  or  less r5  inch  (4-mesh) 

In  reducing  the  gross  sample,  when  the  quantity  reaches  less 
than  125  Ibs.  it  should  be  placed  on  a  mixing  canvas  about  6X8 
feet  and  mixed  by  raising  first  one  end  of  the  canvas  and  then  the 
other,  so  as  to  roll  the  coal  back  and  forth. 

The  sample  should  be  worked  down  as  rapidly  as  possible  to 
avoid  loss  of  moisture  and  immediately  placed  in  an  air-tight  can 
or  container.  The  outside  of  the  container  should  be  plainly 
marked  and  the  corresponding  description  placed  inside. 

Data. — The  following  data  should  accompany  the  sample: 

Coal  delivered  to 

Sampled  by Date 

Amount  taken  for  original  sample 

Amount  of  coal  sample  represents 

Sampled  from  barge,  car  or  pile 

Car  (initial  and  number) 

Barge  or  vessel 

Trade  name  of  coal 

Grade  (f ,  slack,  nut,  run-of-mine,  etc) 

Remarks  (appearance  of  coal,  lumps,  slate,  sulphur  balls,  weather  conditions, 

etc.) 

Sold  by Mined  by 

County State Mine 

REFERENCE. — This  is  essentially  the  Standard  Method  of  the  American 
Society  for  Testing  Materials,  adopted  1916,  Serial  D-21-16. 


172  TECHNICAL  METHODS  OF  ANALYSIS 

COAL 
Proximate  Analysis  and  Heating  Value 

Preparation  of  Laboratory  Sample. — (A)  When  Coal  Appears 
Dry. — If  the  sample  is  coarser  than  4-mesh  (^  inch)  and  larger  in 
amount  than  10  Ibs.,  quickly  crush  it  with  jaw  crusher  to  pass  a  4- 
mesh  sieve  and  reduce  by  a  riffle  to  between  5-10  Ibs.  Then 
grind  the  whole  sample  to  20-mesh  size.  If  moisture  is  of  special 
importance,  remove  about  60  grams  immediately  with  a  spoon 
from  various  parts  of  the  sample  and  place  at  once  in  a  dry  rubber- 
stoppered  bottle.  This  sample  is  to  be  used  for  the  determination 
of  total  moisture. 

Thoroughly  mix  the  main  portion  of  the  sample,  reducing  on  a 
small  riffle  to  about  120  grams,  and  pulverize  to  60-mesh.  If 
desired,  this  60-mesh  sample  may  be  further  reduced  by  a  small 
riffle  to  2-3  ounces. 

The  sample  will  become  partly  dry  on  grinding,  hence  if  moist- 
ure is  important,  compute  the  analysis  of  the  60-mesh  sample  to 
the  "  bone  dry  "  basis  by  dividing  each  result  by  1  minus  the 
moisture  content  expressed  as  a  decimal.  Compute  the  analysis 
of  the  coal  "  as  received  "  from  the  bone  dry  analysis  by  multi- 
plying each  figure  by  1  minus  the  total  moisture  found  in  the 
larger  20-mesh  sample,  also  expressed  as  a  decimal. 

(B)  When  Coal  Appears  Wet. — Spread  the  whole  sample  on 
weighed  pans;  weigh  quickly  and  air-dry  in  a  special  drying  oven 
at  10-15°  C.  above  room  temperature.  Continue  drying  until 
the  loss  in  weight  is  not  more  than  0.1%  per  hour.  Then  finish 
sampling  as  above  under  dry  coal.  When  moisture  is  important 
correct  the  moisture  found  in  the  20-mesh  air-dried  sample  to 
total  moisture  "  as  received  "  as  follows: 

100  —  per  cent  air-drying  loss 

— — —        — X  (per  cent    H20   in  20-mesh)  + 

J-UU 

(per  cent  air-drying  loss)  =  (total  moisture  as  received) . 

Compute  the  analysis  to  the  bone-dry  basis  and  the  "  as 
received  "  basis  as  under  dry  coal  above,  using  for  the  "  as  re- 
ceived "  computation  the  total  moisture  as  found  by  the  above 
formula  in  place  of  the  moisture  found  in  the  20-mesh  coal. 

NOTES. — (1)  In  the  general  run  of  coal  analysis  the  actual  moisture  is 
not  important,  as  most  purchases  are  based  on  bone-dry  figures.  In  such 


ANALYSIS  OF  FUELS  173 

it  is  not  necessary  to  take  a  special  20-mesh  sample,  but  wet  coal  should 
always  be  air-dried  before  grinding.  In  the  latter  case  the  formula  for  cor- 
recting to  total  moisture  "  as  received  "  becomes 

190— per  cent  air  drying  loss 

— — r —  —  X(per  cent  H2O  in  60-mesh  sample)  +  (per 

100 

cent  air-drying  loss). 

(2)  Freshly  ground  or  wet  coal  loses  moisture  rapidly,  hence  sampling 
operations  between  opening  the  container    and  taking  the  20-mesh  total 
moisture  sample  must  be  conducted  as  quickly  as  possible  with  very  little 
exposure  to  air. 

(3)  The  accuracy  of  the  method  of  preparing  laboratory  samples  should  be 
checked  frequently  by  re-sampling  rejected  portions  and  preparing  a  duplicate 
sample.     Ash  determinations  on  the  two  samples  should  not  differ  more  than 
the  following  limits: 

No  carbonates  present 0 . 4% 

Considerable  carbonate  and  pyrite  present 0.7% 

Ash  over  12%  (containing  considerable  carbonate  and  pyrite) 1-0% 

Moisture. — Weigh  1  gram  of  the  60-mesh  sample  quickly  and 
accurately  in  a  15  cc.  weighed  platinum  crucible  with  tight-fitting 
capsule  cover,  previously  heated  and  cooled  in  a  desiccator  over 
H2S04.  Place  in  the  special  moisture  oven  with  cover  removed 
and  dry  for  exactly  one  hour  at  104-108°  C.  Remove  and 
place  the  crucible  with  tight-fitting  cover  in  a  desiccator  over 
cone.  H2SO4.  When  cool,  immediately  weigh  the  covered  cru- 
cible. Report  the  loss  of  weight  as  moisture. 

NOTES. — (1)  The  moisture  determination  is  made  in  a  specially  designed 
double-walled  oven.  The  space  between  the  walls  is  filled  with  a  glycerin-water 
mixture  of  such  strength  that  the  boiling  point  is  between  104°  C.  and  108°  C. 
Concentration  of  the  solution  is  prevented  by  means  of  a  reflux  condenser  fitted 
into  the  top  of  the  oven.  Air  is  pre-dried  by  passing  it  through  cone.  H2SO4 
at  such  a  rate  that  the  air  is  renewed  in  the  oven  2-4  times  a  minute.  The 
pre-dried  air  is  then  led  through  .a  coil  of  block  tin  tubing  which  passes  through 
the  heated  solution  of  glycerin  and  water.  Air  is  thus  pre-heated  before  enter- 
ing the  oven.  It  escapes  by  means  of  a  small  orifice  in  the  door  of  the  oven. 

(2)  Permissible  tolerances: 

Same  analyst      Different  analysts 

Moisture  under  5% 0.2%  0.3% 

Moisture  over  5% 0.3%  0.5% 

Volatile  Matter. — Place  the  crucible  with  tight-fitting  capsule 
cover  containing  the  residue  from  the  moisture  determination  on  a 
nichrome  wire  triangle  and  heat  for  exactly  seven  minutes  over  a 


174  TECHNICAL  METHODS  OF  ANALYSIS 

Tirrill  burner  burning  artificial  gas.  The  temperature  at  the 
bottom  of  the  crucible  must  be  regulated  by  means  of  a  thermo- 
couple so  that  it  is  maintained  at  950°  C.  (±20°  C.).  Burner  and 
crucible  are  protected  by  a  wind  shield.  Cool  in  air  and  weigh 
without  disturbing  the  cover.  The  further  loss  of  weight  thus 
obtained  is  reported  as  volatile  matter. 

Permissible  tolerances: 

Same  analyst  Different  analysts 

Bituminous  coals 0.5%  1-0% 

Lignites 1.0%  2.0% 

Fixed  Carbon. — Place  the  crucible  containing  the  residue 
from  the  Volatile  Matter  determination  (coke)  in  an  artificial  gas- 
fired  muffle  which  is  maintained  at  a  temperature  of  900-950°  C. 
Continue  heating  until  no  particles  of  unburned  coal  appear  upon 
stirring  with  a  platinum  stirring  wire.  Cool  in  air  and  weigh  with 
cover  as  soon  as  cold.  Report  the  further  loss  in  weight  thus 
obtained  as  fixed  carbon. 

Ash. — The  residue  from  the  last  burning  in  the  muffle  is  the 
ash. 

NOTES. — (1)  The  result  thus  obtained  is  "  unconnected  ash  "  and  is  the  ash 
percentage  always  reported  unless  otherwise  specified. 

(2)  High  ash  coals  require  longer  heating  than  low  ash  coals. 

(3)  Permissible  tolerances: 

Same  analyst  Different  analysts 

No  carbonates  present 0.2%  0.3% 

Carbonates  present 0.3%  0.5% 

More  than  12%  ash,  containing  carbon- 
ate and  pyrite 0.5%  1.0% 

Sulfur. — Weigh  1.3734  grams  of  60-mesh  sample  and  thor- 
oughly mix  on  glazed  paper  with  3  grams  of  Eschka  mixture. 
Transfer  the  uniform  mixture  to  a  30  cc.  Coors  glazed  porcelain 
crucible  and  cover  with  about  1  gram  of  Eschka  mixture. 

Place  the  crucible  in  the  cold  gas-fired  muffle  and  gradually 
raise  the  temperature  to  870-925°  C.  (cherry-red  heat)  in  about 
one  hour.  Maintain  the  maximum  temperature  for  about  one- 
half  hour  and  then  let  the  crucible  cool  in  the  muffle.  When 
burning  is  complete,  all  trace  of  black  coal  will  have  disappeared 
and  only  a  light,  reddish  gray  mass  remains.  Make  sure  such  is 
the  case. 


ANALYSIS  OF  FUELS  175 

When  cool,  empty  the  contents  into  a  150  cc.  beaker  and 
digest  with  75-100  cc.  of  hot  distilled  water  on  the  hot  plate  for 
thirty  to  forty-five  minutes  with  occasional  stirring.  Then  filter 
through  a  rapid  11  cm.  filter  paper.  Wash  the  insoluble  matter 
by  decant ation.  After  several  washings  in  this  manner,  transfer 
the  insoluble  matter  to  the  filter  and  wash  5  times  with  hot  dis- 
tilled water,  keeping  the  mixture  well  agitated.  Treat  the  fil- 
trate, amounting  to  about  250  cc.,  with  10  cc.  of  saturated  bro- 
mine water,  make  slightly  acid  with  cone.  HC1  (5  cc.)  and  boil  to 
expel  liberated  Br.  Make  sure  the  solution  is  acid  by  testing  with 
litmus.  Add  slowly  from  a  pipette,  with  constant  stirring,  10  cc. 
of  a  10%  solution  of  BaCl2-2H20.  Continue  boiling  for  fifteen 
minutes  and  let  stand  overnight  just  below  boiling  point.  The 
solution  is  now  clear  and  the  BaSQi  precipitate  is  granular. 

Filter  through  an  ashless  11  cm.  filter  paper  and  wash  with 
hot  distilled  water  until  a  drop  of  AgNOs  solution  shows  no  precip- 
itate in  the  filtrate.  Place  the  wet  filter  containing  the  pre- 
cipitate of  BaSC>4  in  a  weighed  alundum  (No.  0  or  00)  or  platinum 
crucible,  allowing  free  access  of  air  by  folding  the  paper  over  the 
precipitate  loosely  to  prevent  spattering.  Place  in  a  cold  muffle 
and  smoke  the  paper  off  gradually.  At  no  time  let  it  burn  with  a 
flame.  After  the  paper  is  practically  consumed,  raise  the  tem- 
perature to  approximately  900°  C.  and  heat  to  constant  weight. 
Cool  and  weigh  the  crucible  and  precipitate.  Calculate  to  sulfur. 

CALCULATION. — Grams  of  BaSO4XlO  =  per  cent  sulfur. 

NOTES. — (1)  Always  run  a  blank  determination  with  each  analysis,  using 
the  same  amounts  of  all  reagents  that  were  employed  in  the  regular  determina- 
tion. Deduct  the  sulfur  found  in  the  blank  from  the  amount  found  in  the 
sample. 

(2)  Examine  the  residue  of  Eschka  mixture  for  sulfur  after  digesting  by 
dissolving  it  in  HC1  and  treating  with  bromine  water  and  BaCl2.     When  an 
appreciable  amount  of  sulfur  is  found  add  it  to  the  main  precipitate. 

(3)  Determinations  of  -ash  in  coal  or  coke  must  not  be  made  in  the  same 
muffle  at  the  same  time  with  sulfur  determinations. 

(4)  Reagents  and  Solutions.— Eschka  Mixture:    Mix  2  parts  by  weight  of 
light  calcined  MgO  and  1  part  by  weight  of  anhydrous  Na2CO3.     Both  mate- 
rials should  be  free  as  possible  from  sulfur.     Grind  the  materials  together  and 
after  thoroughly  mixing  pass  through  an  ordinary  flour  sieve.     Keep  the 
mixture  in  glass-stoppered  bottle. 

Saturated  Bromine  Water:  Add  excess  of  bromine  to  1000  cc.  of  distilled 
water  and  mix, 


176  TECHNICAL  METHODS  OF  ANALYSIS     • 

Barium  Chloride  Solution:  Dissolve  100  grams  of  BaCl2-2H2O  in  distilled 
water,  and  dilute  to  1000  cc. 

(5)  Permissible  Tolerances: 

Same  analyst       Different  analysts 

Sulfur  under  2% 0.05%  0.10% 

Sulfur  over  2% 0.10%  0.20% 

Heating  Value  (B.T.U.). — The  calorimetrrc  determination  for 
British  Thermal  Units  is  made'  in  an  Emerson  bomb  calorimeter 
with  a  gold  lining. 

Weigh  accurately  1  gram  of  the  60-mesh  sample  into  the  fuel 
tray  lined  with  recently  ignited  asbestos.  Bituminous  coal  may 
be  used  either  in  the  form  of  a  briquette  or  as  a  powder.  In  the 
cases  of  anthracite  and  coke,  the  powder  is  always  used. 

Set  the  tray  in  place  with  the  iron  wire  connecting  the  terminals 
touching  the  coal.  The  iron  wire  used  should  be  about  No.  34 
B.  &  S.  gauge  and  the  heat  due  to  it  must  be  subtracted  from  the 
final  result.  3-|  inches  of  No.  34  iron  wire  have  a  heating  value  of 
25  B.T.U. 

Place  1-2  cc.  of  water  in  the  bottom  of  the  bomb  to  saturate 
with  moisture  the  oxygen  used  for  combustion.  Screw  the  lid  down 
tightly  against  the  lead  gasket.  Then  force  oxygen  into  the  bomb 
very  slowly  until  the  pressure  within  registers  18-20  atmospheres. 
At  this  point  close  the  needle-point  valve  just  tight  enough  to 
prevent  leakage  of  gas. 

Place  the  bomb  in  the  bucket  containing  exactly  1795  grams  of 
water  at  a  temperature  about  4°  C.  lower  than  room  temperature. 
In  the  cases  of  anthracite  screenings  and  fuels  whose  heating  value 
is  low,  the  temperature  of  the  water  should  be  about  3.5°  C.  lower 
than  room  temperature.  The  initial  temperature  of  the  water  in 
the  bucket  should  be  so  adjusted  that  the  final  temperature  after 
combustion  will  be  approximately  0.5°  C.  above  room  tempera- 
ture, under' which  conditions  the  total  correction  for  heat  gained 
from  or  lost  to  the  surroundings  will  be  small  when  the  rise  of 
temperature  is  3.5-3.7°  C. 

Connect  the  current  terminals,  adjust  the  stirring  apparatus, 
cover  the  calorimeter  jackets,  attach  the  stirring  device  and  insert 
the  thermometer.  Before  taking  any  readings,  allow  the  stirrer 
to  mix  the  water  thoroughly  for  two  or  three  minutes. 

Thermometers  used  for  all  temperature  observations  in  cal- 


ANALYSIS  OF  FUELS  177 

orimetric  work  should  be  graduated  to  0.01°  C.  and  calibrated 
by  the  U.  S.  Bureau  of  Standards.  Correct  all  readings  according 
to  the  calibration  certificate  from  the  Bureau  of  Standards.  Before 
each  reading  tap  the  thermometer  slightly  to  avoid  errors  caused 
by  lag  of  the  mercury  meniscus.  Read  all  temperature  observa- 
tions to  0.001°  C.  with  the  special  reading  lens. 

The  actual  determination  is  divided  into  three  five-minute 
periods:  (1)  the  preliminary  period;  (2)  the  combustion  period; 
and  (3)  the  final  period. 

Take  readings  at  intervals  of  one  minute  during  the  preliminary 
period.  Immediately  at  the  end  of  the  fifth  minute  turn  on  the 
current  of  approximately  12  volts  for  about  one-half  second,  which 
ignites  the  coal.  Continue  readings  at  intervals  of  one-half 
minute  during  the  combustion  period.  Then  take  readings  at 
intervals  of  one  minute  during  the  final  period. 

After  the  last  reading  of  the  final  period  take  the  bomb  out  of 
the  bucket  and  reduce  the  pressure  in  the  bomb  to  atmospheric 
pressure  by  opening  the  needle-point  valve.  Remove  the  lid  and 
very  carefully  inspect  the  interior  of  the  bomb  for  traces  of  un- 
burned  coal  and  iron  wire.  If  any  trace  of  unburned  coal  is 
evident,  the  determination  is  worthless.  A  correction  for  any 
unburned  wire  must  be  made. 

Wash  out  the  bomb  and  fuel  tray  thoroughly  with  distilled 
water  and  titrate  the  washings  with  methyl  orange  and  standard 
Na2COs  solution  of  such  strength  that  1  cc.  is  equivalent  to 
0.004896  gram  of  HN03,  the  heat  of  formation  of  which  is  2  B.T.U. 

Make  a. correction  of  23  B.T.U.  for  each  per  cent  of  sulfur 
present.  This  corrects  for  the  difference  between  the  heats  of 
formation  of  HNOs  and  of  862  to  SOs,  and  also  for  the  Fe  present 
in  the  coal  as  pyrites  being  burned  to  Fe2Os. 

SOLUTIONS. — (1)  Titrating  Solution. — Dissolve  4.122  grams  of 
c.  P.  anhydrous  Na2COs  in  1000  cc.  of  distilled  water.  1  cc.  of 
this  solution  is  equivalent  to  2  B.T.U.  per  pound. 

(2)  Indicator. — Dissolve  1  gram  of  methyl  orange  in  1000  cc. 
of  distilled  water. 

CALCULATION. — The  difference  between  the  final  and  the  initial 
corrected  temperature  observations  of  the  preliminary  period, 
divided  by  7,  gives  the  rate  of  change  during  the  preliminary 
period. 


178  TECHNICAL  METHODS  OF  ANALYSIS 

The  difference  between  the  final  and  initial  corrected  tem- 
perature observations  of  the  combustion  period  gives  the  cor- 
rected observed  rise  in  temperature  during  the  combustion  period. 

The  difference  between  the  initial  and  final  corrected  tempera- 
ture observations  of  the  final  period,  multiplied  by  f,  gives  the 
rate  of  change  during  the  final  period. 

When  the  final  reading  is  greater  than  the  initial  reading,  the 
difference  is  a  minus  quantity;  and  when  the  final  reading  is 
less,  the  difference  is  plus. 

Add  the  algebraic  sum  of  the  rates  of  change  of  the  preliminary 
and  final  periods  to  the  observed  rise  of  temperature  of  the  com- 
bustion period,  and  multiply  the  corrected  rise  in  temperature 
by  the  water  equivalent  factor  of  the  apparatus.  This  product  is 
the  iota7  heat  developed,  expressed  in  B.T.U.  This  must  be 
corrected  for  Fe  wire,  sulfur,  and  "  titer  "  (acid  formed)  as  below. 

Multiply  the  "  titer  "  reading  (number  of  cc.  of  Na2COs  solu- 
tion) by  2,  since  each  cc.  is  equivalent  to  2  B.T.U.  Add  this 
product  to  the  heating  value  of  the  Fe  wire  used,  and  deduct  the 
sum  from  the  total  heat  developed. 

Multiply  the  per  cent  of  sulfur  in  the  sample  by  23  and  deduct 
this  product  also  from  the  total  heat  developed.  The  result  after 
all  these  corrections  is  the  heating  value  of  the  sample  in  B.T.U. 
per  pound. 

Permissible  Tolerances : 

Same  analyst      Different  analysts 

12,000  B.T.U 36  60 

13,000  B.T.U 39  65 

14,000  B.T.U 42  70 

15,000  B.T.U 45  75 

Standardization  of  Calorimeter. — The  accuracy  of  all  calorN 
metric  determinations  depends  upon  the  correct  determination 
of  the  water  equivalent  value  of  the  apparatus.  Standardize 
the  apparatus  by  means  of  naphthalene  and  benzoic  acid  whose 
heats  of  combustion  have  been  determined  by  the  U.  S.  Bureau  of - 
Standards.  The  pure  substances  should  show  the  following  heat- 
ing values: 

Per  Gram 

Naphthalene 9622  calories* 

Benzoic  acid 6329  calories 

*  Calories  per  gram XI. 8  =  B.T.U.  per  pound. 


ANALYSIS  OF  FUELS  179 

The  determination  is  made  under  exactly  the  same  conditions 
as  in  the  determination  on  coal.  Instead  of  using  1  gram  of 
naphthalene  or  benzoic  acid,  however,  as  in  the  case  of  coal,  the 
following  weights  are  taken : 

Naphthalene 0.8450-0.8550  gram 

Benzoic  acid 1.2850-1.2950  grams 

Make  a  pill  of  the  naphthalene  of  the  above  weight  and  imme- 
diately weigh  it  accurately  and  place  in  the  bomb.  Also  make  the 
benzoic  acid  into  pills,  but  place  these  pills  in  a  desiccator  over 
cone.  H2SO4  for  about  eight  hours.  Then  take  the  required 
weight  and  place  immediately  in  the  bomb. 

CALCULATION. — Let  a  =  Wt.  of  material  multiplied  by  its  heat- 
ing value  in  calories ; 

b  =  Heating  value  of  iron  wire  in  calories;* 
c= Heating  value  of  titer  in  calories;* 
d  =  Corrected  rise  in  temperature,  °  C.; 
e  =  Wt.  of  water  in  grams ; 
and      g  =  Water  equivalent  of  apparatus  in  grams ; 

a+6+c 

then    g  = e. 

d 

The  average  of  the  naphthalene  and  benzoic  acid  results  should 
agree  within  approximately  2  grams.  Take  for  the  water  equiva- 
lent in  grams  of  the  apparatus  the  average  of  the  results  by  naph- 
thalene and  by  benzoic  acid. 

The  final  water  equivalent  factor  is  the  water  equivalent  in 
•grams  plus  the  weight  of  water  in  grams,  multiplied  by  1.8.  This 
factor  is  to  be  used  for  converting  the  corrected  temperature  rise 
of  the  coal  to  B.T.U.  per  pound. 

NOTE. — "  H  "Value:  If  it  is  assumed  that  the  calorific  value  of  coal  is  due  to 
combustion  of  organic  matter  and  sulfur,  it  would  seem  probable  that  in  coals  of 
like  character  the  calorific  value  would  be  proportional  to  the  amount  of  these 
substances  present.  Therefore,  if  the  sum  of  these  percentages  of  moisture,  ash 
and  sulfur  be  subtracted  from  100,  the  remainder  would  be  approximately  the 
organic  matter  in  the  coal ;  and  if  the  calorific  value  of  the  sulfur  be  subtracted 
from  the  calorific  value  of  the  coal  as  determined,  the  remainder  should  be  the 
calorific  value  of  the  organic  matter  present.  The  calorific  value  of  coal  cal- 
culated on  a  moisture-ash-sulfur-free  basis  is  commonly  designated  as  "  H." 

*  B.T.U. -i- 1.8  =  calories. 


180  TECHNICAL  METHODS  OF  ANALYSIS 

This  "  H  "  value  differs  for  different  grades  of  coal  but  for  the  same  kind  of 
coal  from  the  same  seam  is  fairly  constant.  The  value  of  "  H,"  being  known 
for  various  grades  of  coals,  serves  as  an  approximate  check  on  the  analysis. 

Calculation  of  "  H."— Let  A  =B.T.U.  as  determined; 

B  =  per  cent  of  sulfur  expressed  as  decimal; 
C  =  per  cent  of  moisture  expressed  as  decimal; 
and  D  =  per  cent  of  ash  expressed  as  decimal; 

A-4Q5QB 
then      "H"  =  —  — . 

1-(B+C+D) 

REFERENCE. — The  procedures  in  this  method  are  essentially  those  of  the 
American  Society  for  Testing  Materials  described  in  its  Book  of  Standards. 

COAL 

Ultimate  Analysis 

Apparatus  and  Chemicals. — (A)  The  combustion  is  made  in  a 
25-burner  combustion  furnace  of  the  Glaser  type. 

(B)  The  purifying  trains  through  which  the  air  and  oxygen 
are  passed  before  they  enter  the  combustion  tube  are  arranged 
in  duplicate,  one  part  for  air,  the  other  for  oxygen,  both  being 
connected  to  the  combustion  tube  by  means  of  a  Y-tube.     The 
purifying  reagents,  arranged  in  the  order  of  the  flow  of  oxygen  or 
air  through  them,  are:  (1)  cone.  H2S04,  (2)  30%  KOH  solution, 
(3)  soda-lime,  and  (4)  granular  CaC^. 

The  oxygen  and  air  are  allowed  to  bubble  through  about 
0.25  inch  of  the  reagents  (1)  and  (2),  which  are  in  gas-washing 
bottles.  Reagents  (3)  and  (4)  are  in  U-tubes. 

(C)  The  combustion  tube  is  about  40  inches  long  and  about 
f  inch  (16  mm.)  internal  diameter,  made  of  hard  glass  or  silica. 
The  tube  extends  beyond  each  end  of  the  furnace  for  a  distance 
of  about  4  inches,  the  ends   of  the  tube  being  protected  from 
the  heat  of  the  furnace  by  closely  fitting  circular  shields  of  asbes- 
tos.    The  rear  end  of  the  tube  (the  end  next  to  the  purifying 
train)  is  closed  with  a  rubber  stopper.    As  this  end  of  the  tube  is 
kept  cool  by  the  protection  of  the  circular  shield  and  by  the  pas- 
sage of  cool  air  and  oxygen,  there  is  very  little  danger  of  volatile 
products  being  given  off  by  the  rubber.    The  other  end  of  the 
tube  is  closed  by  a  well-rolled  cork  of -specially  selected  quality, 
the  danger  from  overheating  at  this  end  of  the  tube  being  too  great 
to  permit  of  the  use  of  the  more  convenient  rubber  stopper. 


ANALYSIS  OF  FUELS  181 

The  tube  is  filled  as  follows:  A  space  of  5-5.5  inches  is  left 
empty  at  the  end  nearest  the  absorbing  train.  Then  follow: 
(1)  a  plug  of  asbestos;  (2)  4-5  inches  of  fused  PbCrC>4  in  small 
lumps;  (3)  an  asbestos  plug;  (4)  14-16  inches  of  pure,  recently 
ignited  "wire"  CuO  (or  a  close  coil  of  fine  copper  gauze  thor- 
oughly oxidized  by  heating  it  in  a  stream  of  pure  oxygen) ;  (5) 
an  asbestos  plug;  (6)  the  boat  for  holding  the  coal.  There  must 
be  12-14  inches  of  empty  tube  following  the  last  asbestos  plug, 
so  that  the  part  of  the  tube  in  which  the  boat  is  placed  will  be  well 
in  the  furnace,  and  yet  the  tube  itself  project  at  least  4  inches  out- 
side of  the  furnace. 

(D)  The  absorption  train  is  as  follows :  The  water  is  absorbed 
in  a  6-inch  U-tube,  filled  with  granular  CaC^ ;  the  C02  is  absorbed 
by  KOH  (30%  solution  *)  in  an  ordinary  Liebig  bulb,  to  which  is 
attached  a  3-inch  U-tube  containing  soda-lime  and  granular  CaC^, 
the  bulb  and  U-tube  being  weighed  up  together.  This  is  followed 
by  a  final  guard  tube  filled  with  CaCb  and  soda-lime  to  prevent 
any  back-pressure  of  CC>2  or  H^O.  The  gases  formed  during 
combustion  are  drawn  through  the  train  by  suction,  a  Marriott 
bottle  being  used  to  secure  a  constant  suction  head. 

(E)  The  oxygen  used  is  kept  over  water  and  is  supplied  under 
small  pressure.  The  supply  of  oxygen  and  the  aspiration  during 
a  combustion  are  so  regulated  as  to  keep  the  difference  in  pressure 
between  the  inside  and  outside  of  the  tube  very  small,  the  pressure 
inward  being  slightly  greater.  This  reduces  the  danger  of  leaks 
to  a  minimum,  and,  if  by  chance  any  slight  leakage  does  occur, 
it  is  inward  rather  than  outward  and  the  effect  upon  the  deter- 
mination is  small. 

Testing  the  Apparatus. — Before  beginning  the  determination 
test  the  apparatus  for  leaks  by  starting  the  aspirator  at  the  rate  of 
3  bubbles  of  air  per  second  through  the  KOH  bulb  and  then  shut- 
ting off  the  supply  of  air.  If  not  more  than  1  bubble  of  air  per 
minute  passes  through  the  KOH  bulb,  the  connections  are  suf- 
ficiently tight  to  proceed  with  the  determination.  Air  is  then 
admitted  to  the  purifying  apparatus,  the  tube  heated  to  redness 
throughout  and  1000  cc.  or  more  of  air  aspirated.  The  KOH  bulb 
and  drying  tube  are  then  detached  and  weighed.  They  are  again 

*  To  this  should  be  added  a  little  KMnO4  to  oxidize  any  possible  oxidizable 
impurities. 


182  TECHNICAL  METHODS  OF  ANALYSIS 

connected  up  and  500  cc.  of  oxygen,  followed  by  1000  cc.  of  air, 
are  aspirated  through  the  train. 

On  commencing  the  second  aspiration,  the  burners  under  the 
rear  portion  of  the  tube  are  gradually  turned  down  and  finally 
entirely  out,  so  that  the  empty  portion  of  the  tube  into  which  the 
sample  for  analysis  is  to  be  inserted  becomes  nearly  or  quite  cool 
by  the  time  the  aspiration  is  complete.  The  burners  under  the 
two-thirds  of  the  CuO  next  to  the  PbCr04  are  kept  lighted  and  this 
portion  of  the  CuO  kept  at  a  red  heat.  After  aspiration  of  the 
1000  cc.  of  air,  the  KOH  bulb  and  drying  tube  are  detached  and 
again  re  weighed.  If  the  gain  or  loss  in  weight  is  less  than  0.0005 
gram,  the  apparatus  is  ready  for  an  analysis. 

Carbon  and  Hydrogen. — Ignite  and  cool  the  boat.  Weigh  it 
empty  in  a  glass-stoppered  weighing  bottle.  Place  in  it  about  0.2 
gram  of  the  finely  pulverized  and  well-mixed  air-dry  coal.  (The 
sample  must  be  ground  very  fine,  otherwise,  in  weighing  so  small  a 
quantity,  average  results  will  not  be  obtained.)  Place  the  boat  in 
the  bottle,  quickly  stopper  and  weigh  accurately.  Insert  the  boat 
quickly  into  its  proper  place  in  the  combustion  tube  and  connect 
up  the  apparatus. 

The  tube  should  be  cool  after  -the  first  12  inches,  the  CuO 
should  be  red  hot  and  the  PbCrO4  at  a  dull  red  heat.*  The  boat 
should  be  transferred  from  the  weighing  bottle  to  the  combustion 
tube  as  rapidly  as  possible  to  avoid  change  in  moisture  content 
and  should  be  placed  near  the  asbestos  plug  at  the  beginning  of 
the  CuO  section. 

After  connecting  up  the  apparatus,  start  the  aspiration  with 
pure  oxygen  at  the  rate  of  3  bubbles  per  second.  Turn  on  one 
burner  about  4  inches  back  from  the  boat  and  continue  aspiration 
carefully  until  practically  all  moisture  is  expelled  from  the  sample. 
Then  increase  the  heat  very  gradually  until  all  the  volatile  matter 
has  been  driven  off.  In  doing  this,  the  heat  must  be  applied  grad- 
ually in  order  to  prevent  a  too  rapid  evolution  of  gas  and  tar 
which  might  either  escape  complete  combustion  or  be  driven 
back  into  the  purifying  train.  The  heat  should  be  slowly  increased 
by  turning  on  more  burners  under  the  open  part  of  the  tube  until 
the  sample  is  ignited;  then  increase  the  temperature  rapidly, 

*  When  silica  tubes  are  used,  the  PbCrO4  section  should  be  kept  slightly 
below  even  a  dull  red  on  account  of  danger  of  fusing  the  tube. 


ANALYSIS  OF  FUELS  183 

taking  care,  however,  not  to  melt  the  combustion  tube.  Any 
moisture  collecting  in  the  end  of  the  combustion  tube  or  in  the 
rubber  connection  joining  it  to  the  CaCb  tube  is  driven  over 
into  the  CaCl2  tube  by  carefully  warming  with  a  piece  of  hot  tile. 
The  aspiration  with  oxygen  is  continued  for  two  minutes  after  the 
sample  ceases  to  glow,  the  heat  is  then  turned  off  and  about  1200 
cc.  of  air  aspirated  through  the  tube.  Finally,  the  absorption 
bulbs  are  disconnected,  wiped  with  a  clean  cloth  and  allowed  to 
cool  in  the  balance  room  until  they  come  to  room  temperature  and 
then  weighed.  Calculate  the  per  cent  of  carbon  and  of  hydrogen 
by  the  following  formulas: 

'  (increase  in  weight  of  KOH  bulb) 

Weight  of  sample 

(increase  in  weight  of  CaCl2  tube) 
70  H=11.19X .  .       -          .  . 

Weight  of  sample 

NOTES. — (1)  After  the  boat  has  been  removed,  the  apparatus  is  ready  for 
another  determination,  since  any  CuO  will  all  have  been  reoxidized  by  the  air 
current. 

(2)  After  removing  the  boat,  weigh  the  ash  (unless  the  ash  has  been  deter- 
mined on  another  sample)  and  carefully  inspect  it  for  any  unburned  carbon. 
If  such  is  found,  the  determination  is  worthless  -and  must  be  repeated. 

(3)  The  wire  CuO  should  be  used,  as  the  ordinary  granular  oxide  some- 
times contains  carbon  and  carbonates.     It  should  be  examined  for  CaCOs 
or  other  carbonates  which  are  likely  to  give  off  CO2  on  heating,  and  also  for 
lime  which  may  absorb  CO2.     The  CuO  may  be  tested  for  CaO  by  extracting 
it  with  a  little  dil.  HNO3,  adding  NH4OH  in  excess  and  then  testing  the  liquid 
with  (NH4)2C2O4.     It  should  give  no  precipitate. 

(4)  The  asbestos  used  should  be  boiled  in  HC1,  washed,  dried  and  ignited, 
in  order  to  remove  traces  of  CaCO3  or  other  carbonates  sometimes  present. 

(5)  The  PbCrO4  should  be  in  moderately  coarse  lumps  from  which  all  fine 
material  has  been  sifted  out  with  a  20-  or  30-mesh  sieve.     It  must  be  neutral 
and  free  from  alkaline  chromaies.     The  same  PbCrO4  can  be  used  for  many 
determinations;   as  long  as  it  does  not  turn  green  for  more  than  20%  of  its 
length  in  the  tube,  it  is  perfectly  safe. 

(6)  The  oxygen  should  be  tested  as  to  its  purity  and  must  not  be  kept  in 
rubber  bags  or  passed  through  long  rubber  tubes. 

(7)  Check  determinations  should  agree  within  0.07%  for  H,  0.30%  for 
C  and  0.05%  for  N. 

Nitrogen. — Weigh  1  gram  of  the  finely  pulverized  coal  into  a 
Kjeldahl  distilling  flask  and  determine  the  nitrogen  by  the  Gunning 
method  as  described  on  page  65. 


184  TECHNICAL  METHODS  OF  ANALYSIS 

Sulfur. — Determine  the  sulfur  as  described  on  page  174. 

Oxygen. — As  no  satisfactory  method  is  known  for  the  direct 
determination  of  the  oxygen  in  coal,  it  is  always  determined  "  by 
difference,"  the  sum  of  the  percentages  of  H,  C,  N,  S,  and  ash 
being  subtracted  from  100%  and  the  remainder  called  oxygen. 
The  result  so  obtained  is  always  inaccurate,  the  error  increasing 
with  the  percentages  of  ash  and  sulfur.  The  weight  of  the  ash 
does  not  represent  that  of  the  mineral  matter  in  the  coal,  the 
pyrite  in  the  coal  being  burned  to  Fe20s  and  the  sulfur  passing  off 
as  862.  Thus  4  atoms  of  S  in  2  FeS2  are  replaced  by  3  atoms  of  O 
in  the  Fe203,  and  the  loss  of  weight  is  equal  to  f  of  the  S.  For 
this  reason  many  chemists  use  f  of  the  S,  instead  of  the  total  S 
found  by  analysis,  in  calculating  the  0.  As  coals  contain  sulfur 
in  other  forms  than  FeS2,  however,  and  also  frequently  other  com- 
pounds that  lose  weight  on  burning,  such  as  FeCOa  and  CaCOs, 
it  is  doubtful  whether  the  results  obtained  in  this  way  are  any 
closer  to  the  truth. 

REFERENCES. — Lord:  "Notes  on  Metallurgical  Analysis,"  pages  165-170. 
Bulletin  No.  9,  Geological  Survey  of  Ohio,  pages  317-319.  U.  S.  Dept.  Agr., 
Div.  Chem.,  Bulletin  No.  46,  Revised,  pages  14-16  (1899).  American 
Society  for  Testing  Materials,  Triennial  Standards,  1918,  page  694. 


PHOSPHORUS  IN  COAL  AND  COKE 

Ignite  to  ash  in  a  platinum  crucible  exactly  10  grams  of  coal  or 
5  grams  of  coke.  Add  15  cc.  of  cone.  HNOs  and  about  5  cc.  of  HF. 
Evaporate  carefully  to  dry  ness  under  a  good  hood.  Fuse  the 
residue  with  3  grams  of  Na2COs  (if  any  unburned  carbon  is  present 
in  the  ash,  0.2  gram  of  NaNOs  should  be  mixed  with  the  Na2COa). 
Leach  out  the  melt  with  water,  filter  and  wash.  Ignite  the  residue 
and  again  fuse  with  Na2C03.  Leach  out  this  melt,  filter  and 
wash.  Acidify  the  combined  filtrates  in  a  flask  with  a  very  slight 
excess  of  HNOs  and  concentrate  to  a  volume  of  100  cc.  Neu- 
tralize with  cone.  NILiOH  and  add  approximately  5  cc.  in  excess. 
Then  make  slightly  acid  with  HNOs,  bring  the  solution  to  a  tem- 
perature of  80°  C.,  add  60  cc.  of  ammonium  molybdate  solution 
and  shake  for  five  minutes.  Complete  the  determination  as 
under  Phosphorus  in  Steel  (page  112),  dissolving  the  yellow 


ANALYSIS  OF  FUELS  185 

precipitate  in  standard  NaOH  solution  and  titrating  the   excess 
with  standard  HNOs  solution. 

REFERENCE. — This  method  is  similar  to  that  of  the  American  Society  for 
Testing  Materials,  Triennial  Standards,  1918,  page  693. 

COAL-ASH  AND  REFUSE 

General. — The  usual  determinations  on  samples  of  coal-ash 
or  refuse  are  the  amounts  of  moisture,  combustible  matter  and  ash, 
and  the  calculation  of  the  B.T.U.  per  pound. 

Moisture. — Dry  1  gram  of  the  finely  powdered  sample  in  a 
weighed  platinum  crucible  for  one  hour  at  110°  C.,  in  the  special 
water-glycerin  bath  described  on  page  173. 

Ash. — Ignite  the  residue  from  the  above  moisture  determina- 
tion in  the  platinum  crucible  in  a  muffle  at  approximately  900°  C., 
until  complete  combustion  is  obtained.  Cool  in  a  desiccator  and 
weigh. 

Combustible  Matter. — Subtract  from  100%  the  percentages  of 
moisture  and  of  ash  as  above  determined.  The  difference  is 
combustible  matter. 

B.T.U.  per  Pound. — The  heating  value  is  calculated  on  the 
arbitrary  basis  of  14,600  B.T.U.  per  pound  of  combustible  matter. 
In  other  words,  multiply  the  percentage  of  combustible  matter, 
expressed  as  a  decimal,  by  14,600. 

NOTE. — It  is  often  customary  to  report  results  on  the  dry  basis.  In  such 
case  divide  the  results  obtained  for  combustible,  ash,  and  B.T.U.,  respectively, 
on  the  "  as  received  "  basis  by  the  difference  between  1.0000  and  the  moisture 
percentage  expressed  as  a  decimal.  In  the  case  of  very  wet  samples,  requiring 
preliminary  air-drying,  proceed  as  under  Coal,  page  172. 

GASOLINE 

General. — The  essential  desirable  properties  in  gasoline  for 
motor  use  are: 

1.  It  should  not  contain  too  large  a  percentage  of  highly  volatile 
products  which  tend  to  cause  large  evaporation  losses  and  excessive 
danger  in  handling  and  storage,  but  should  have  sufficient  volatile 
constituents    to    permit    starting    an    engine    under    reasonably 
unfavorable  conditions  without  pre-heating. 

2.  It    should    not    contain   any    considerable    percentage   of 


186  TECHNICAL  METHODS  OF  ANALYSIS 

heavy  or  non-volatile  constituents  which,  after  atomization  into 
the  engine  cylinders,  cannot  be  completely  vaporized  and  burned. 

3.  It  should  not  contain  any  material  which,  after  combustion, 
leaves  a  residue  which  collects  in  the  motor. 

4.  It  should  be  free  from  substances  which  attack  metal, 
either  before  or  after  combustion.     This  includes  unremoved  acid 
used  in  refining. 

5.  Neither  the  gasoline  nor  its  products  of  combustion  should 
have  a  strong  or  markedly  disagreeable  odor. 

6.  It  should  be  free  from  non-combustible  material  such  as 
water,  sediment,  etc. 

Types  of  Gasoline. — 1.  "  Straight "  Refinery  Gasoline.  In 
general  these  are  made  by  distilling  crude  oil  in  a  fire  still  and 
taking  a  cut  when  the  gravity  of  the  product  reaches  some  pre- 
determined mark.  So-called  crude  naphtha  or  benzine  is  acid 
refined  and  steam  distilled.  Several  products  of  different  ranges 
of  volatility  may  be  produced,  or  the  steam  distillation  may  simply 
separate  the  product  from  the  less  volatile  bottoms  which  go  into 
the  burning  oil  stock. 

"  Straight  "  refinery  gasolines  are  generally  characterized  by  a 
low  content  of  unsaturated  and  aromatic  hydrocarbons,  and  by  a 
distillation  range  free  from  marked  irregularities. 

2.  Blended    Casing-head    Gasoline.     Casing-head    gasoline    is 
obtained  from  natural  gas  by  compression  or  absorption.     It  is 
too  volatile  for  general  use  "  straight  "  and,  before  being  mar- 
keted, is  generally  blended  with  sufficient  heavy  naphtha.     The 
resulting  mixture  is  characterized  in  general  by  a  volatility  range 
showing  a  considerable  percentage  of  constituents  of  low  and  high 
boiling  points,  but  a  lack  of  intermediate  products.     Frequently, 
however,  the  blending  is  done  in  a  manner  difficult  to  detect,  the 
natural  gas  gasoline  being  used  in  moderately  small  proportion 
with  heavy  straight-run  naphtha  in  order  to  make  a  product  hav- 
ing a  desirable  percentage  of  volatile  constituents. 

As  regards  chemical  properties,  blended  casing-head  gasoline 
seems  to  be  identical  with  "  straight  "  refinery  products  of  the 
same  distillation  range.  The  characteristic  physical  properties  of 
blended  gasoline  are  due  wholly  to  the  details  of  blending. 

3.  Cracked  or  Synthetic  Gasoline.     These  are  marketed  largely, 
if    not    altogether,    in    the    form    of    blends    with    "  straight " 


ANALYSIS  OF   FUELS  187 

refinery  and  casing-head  gasoline.  The  cracked  gasolines  are 
similar  to  "  straight  "  refinery  products  in  most  physical  and 
chemical  properties  but  contain  varying  percentages  of  unsat- 
urated  and  aromatic  hydrocarbons. 

Color  and  Odor. — Properly  refined  gasolines  are  water-white 
and  the  color  of  a  sample  as  seen  in  a  4-ounce  sample  cylinder 
should  be  noted.  The  sample  also  should  be  free  from  rank  and 
disagreeable  odors. 

Water  and  Foreign  Matter. — The  sample  should  be  free  from 
water,  sediment,  and  other  foreign  matter.  Water  is  seldom 
present  and  is  easy  to  detect,  as  an  appreciable  amount  will  sep- 
arate into  a  lower  layer. 

Acidity. — Shake  10  cc.  of  the  gasoline  with  5  cc.  of  distilled 
water  and  test  the  water  with  blue  litmus  paper,  which  should  not 
turn  red.  The  amount  of  acid  may  be  determined  quantitatively 
by  taking  a  larger  known  amount  of  gasoline  and  titrating  the 
water  with  0.1  N  or  0.01  N  NaOH  and  phenolphthalein. 

Specific  Gravity. — In  view  of  the  various  sources  of  gasoline 
now  on  the  market,  the  sp.  gr.  is  no  longer  of  any  particular  value 
as  an  index  of  the  quality.  It  may  be  determined  with  a  pyc- 
nometer,  Westphal  balance,  or  hydrometer. 

Distillation. — Conduct  the  distillation  of  100  cc.  of  the 
sample  in  an  Engler  distilling  flask  (in  case  it  is  desired  to  deter- 
mine the  sp.  gr.  of  the  different  fractions,  200-500  cc.  should  be 
employed  for  distillation) . 

(A)  APPARATUS. — The  apparatus  for  the  distillation  is  as  follows: 
(Fig.  10.) 

(I)  Flask.— The  flask  used  is  the  standard  100  cc.  Engler  flask, 
described  in  the  various  textbooks  on  petroleum.  The  dimensions 
are  as  follows: 

Dimensions  Cm.  Inches 

Diameter  of  bulb 6.5  2 . 56 

Diameter  of  neck 1.6  0 . 63 

Length  of  neck 15.0  5.91 

Length  of  vapor  tube 10.0  3.94 

Diameter  of  vapor  tube 0.6  0 . 24 

Position  of  vapor  tube,  9  cm.  (3.55  inches)  above  the  surface  of 
the  liquid  when  the  flask  contains  its  charge  of  100  cc.  The  tube 
is  approximately  in  the  middle  of  the  neck. 


188 


TECHNICAL   METHODS  OF  ANALYSIS 


The  flask  is  supported  on  a  ring  of  asbestos  having  a  circular 
opening  1.25  inches  in  diameter;  this  means  that  only  this  limited 
portion  of  the  flask  is  to  be  heated.  The  use  of  a  sand  bath  is 
not  approved. 


1 

I 


Bureau  of  Mines,  Technical  Paper  166 

FIG.  10. — Apparatus  for  Distillation  of  Gasoline 

(II)  Condenser. — The  condenser  consists  of  a  thin-walled  tube 
of  metal  (brass  or  copper)  0.5  inch  internal  diameter  and  22  inches 
long.  It  is  set  at  an  angle  of  75°  from  the  perpendicular  and 
surrounded  with  a  water  jacket  of  the  trough  type.  The  lower 
end  of  the  condenser  is  cut  off  at  an  acute  angle  and  curved  down 
for  a  length  of  3  inches.  The  condenser  jacket  is  15  inches  long. 

NOTE. — For  ordinary  purposes  in  comparing  different  samples  an  ordinary 
Liebig  condenser  with  an  inner  tube  at  least  22  inches  long  may  be  used. 
The  water  running  through  it  should  be  as  cold  as  possible  and  the  graduated 
cylinder  collecting  the  sample  should  preferably  be  surrounded  by  ice  water. 


ANALYSIS  OF  FUELS  189 

(III)  Thermometer. — The  accuracy  of  the  distillation  primarily 
depends  upon  the  accuracy  of  the  thermometer.  It  should  be  an 
accurate  nitrogen-filled  instrument  with  a  short  bulb  (10-15  mm. 
long).  The  diameter  of  the  thermometer  should  be  between  5.5 
and  7  mm.  and  the  diameter  of  the  bulb  less  than  that  of  the  ther- 
mometer tube.  The  total  length  should  be  approximately  380 
mm.  and  the  range  from  0-270°  C.;  with  the  length  of  the  grad- 
uated portion  between  the  limits  of  210-250  mm.  It  should  be 
scaled  for  total  immersion  with  an  accuracy  of  0.5°  C.  The  above 
requirements  insure  that  nearly  always  the  lowest  temperatures 
registered  will  come  above  the  cork  of  the  distillation  flask  and 
variations  because  of  the  stem  correction  will  always  be  prac- 
tically the  same.  The  stem  correction  should  not  be  applied,  but 
it  should  be  understood  that  results  of  distillations  are  expressed 
in  terms  of  thermometer  readings,  not  of  actual  temperatures. 

METHOD  OF  DISTILLATION. — The  flask  connected  with  the  con- 
denser is  filled  with  a  100  cc.  charge  of  gasoline,  measured  from  a 
100  cc.  graduated  cylinder.  The  same  cylinder  may  be  used, 
without  drying,  as  the  receiving  vessel  for  the  distillate.  Apply 
heat  to  the  flask  in  regulated  degree,  taking  care  that  the  whole 
distillation  from  beginning  to  end  proceeds  at  a  rate  of  not  less 
than  4  nor  more  than  5  cc.  a  minute.  Take  the  readings  of  the 
thermometer  when  the  first  drop  falls  from  the  end  of  the  con- 
denser, also  when  1  cc.  has  distilled  over,  and  then  continue  to 
take  readings  as  every  5  cc.  comes  over,  beginning  at  5  cc.  and 
running  up  to  95  cc.  Record  also  the  dry  point  or  highest  tem- 
perature reading  obtainable  at  the  end  of  the  distillation. 

Determine  the  distillation  loss  by  adding  the  per  cent  of  residue 
in  the  distilling  flask,  after  cooling,  to  the  per  cent  of  total  distil- 
lates held  in  the  receiver.  If  the  distillation  loss  is  over  3%,  make 
a  check  distillation,  as  excessive  loss  may  indicate  that  the  rate 
of  distillation  at  the  beginning  was  too  rapid.  In  case  the  magni- 
tude of  the  loss  is  confirmed  this  fact  is  of  importance  in  indicating 
that  the  gasoline  contains  very  volatile  constituents,  particularly 
those  derived  from  added  casing-head  gasoline. 

Have  the  condenser  trough  filled  with  a  mixture  of  cracked 
ice  and  water  (not  dry  cracked  ice),  and  during  the  distillation 
keep  sufficient  ice  in  the  trough  to  prevent  the  temperature  of  the 
cooling  water  exceeding  8°  C.  (46°  F.) 


190  TECHNICAL  METHODS  OF  ANALYSIS 

If  distillations  are  made  at  high  altitudes  or  when  barometric 
pressures  are  low,  allowances  may  be  made  for  this  factor.  In 
general,  recording  the  barometric  pressure  read  at  the  time  of  the 
distillation  will  suffice,  and  it  is  recommended  that  whenever  there 
is  possibility  of  dispute  over  the  results  of  a  distillation  this  should 
be  done. 

The  thermometer  bulb  should  be  covered  with  a  thin  film  of 
absorbent  cotton;  this  keeps  the  glass  always  wet  with  the  con- 
densate  from  the  vapor  and  thus  prevents  possible  fluctuations 
in  the  temperature.  It  also  tends  to  prevent  superheating  of  the 
bulb  at  the  end  of  the  distillation  and  thus  makes  possible  an 
accurate  determination  of  the  dry  point. 

NOTE. — The  use  of  apparatus  at  least  approximately  as  described  is  essen- 
tial, although  the  method  is  such  that  no  considerable  discrepancies  will  result 
if  the  apparatus  is  not  exactly  standard.  The  chief  source  of  difficulty  is  the 
rate  of  heating  and  the  speed  should  come  within  the  above  limits.  For  the 
most  accurate  work  it  is  advisable  to  have  the  100  cc.  sample  measured  out 
at  the  same  temperature  as  the  condenser  bath,  that  is  33°  F. 

REFERENCES. — Dept.  of  the  Interior,  U.  S.  Bureau  of  Mines,  Technical 
Paper  166,  Petroleum  Technology  39,  May,  1917. 

HEATING  VALUE  AND  SULFUR  CONTENT  OF  LIQUID  FUELS 

General. — This  method  is  to  be  employed  for  determining  the 
B.T.U.  and  sulfur  content  of  such  liquids  as  oils,  coal  tar  products, 
gasoline,  alcohol,  etc. 

Heating  Value — British  Thermal  Units. — Calorimetric  deter- 
minations are  made  in  an  Emerson  bomb  calorimeter  with  a  gold 
lining. 

Weigh  the  liquid  directly  in  a  dried,  weighed,  No.  00  gelatin 
capsule  (Parke,  Davis  &  Co.).  In  order  to  avoid  incomplete 
combustion  from  scattering  of  material  with  explosive  violence,  it 
is  absolutely  requisite  that  the  capsule  be  very  carefully  filled 
so  that  no  air  bubbles  are  enclosed.  To  insure  this  the  liquid  is 
well  shaken  and  a  little  poured  into  a  small  open  dish.  Each 
half  of  the  previously  weighed  capsule  is  filled,  and  while  still 
immersed  the  halves  of  the  capsule  are  fitted  tightly  together. 
Then  remove  the  capsule,  dry  it  thoroughly,  weigh  immediately 
and  place  in  the  fuel  tray,  which  is  lined  with  recently  ignited 
asbestos.  Coil  the  iron  wire  around  the  capsule.  Place  about 


ANALYSIS  OF  FUELS  191 

10  cc.  of  distilled  water  in  the  bottom  of  the  bomb.  Screw  the 
lid  tightly  down  on  the  lead  gasket  and  force  oxygen  slowly  into 
the  bomb.  When  testing  liquids  of  the  nature  of  alcohol,  employ  a 
pressure  of  18-20  atmospheres;  for  those  similar  to  gasoline,  use 
a  pressure  of  30  atmospheres;  and  for  materials  like  fuel  oil  or 
lubricating  oil  use  a  pressure  of  40  atmospheres. 

The  bomb  is  placed  in  the  bucket  which  contains  exactly  1795 
grams  of  water  at  a  temperature  of  approximately  5-5.5°  C. 
lower  than  the  room  temperature.  The  actual  determination  is 
completed  exactly  as  for  Coal  (page  176). 

CALCULATION. — The  result  is  calculated  as  described  on  page 
177.  The  result  thus  obtained  is  further  corrected  as  follows: 

Deduct  from  the  total  B.T.U.  generated  the  weight  of  the 
capsule  multiplied  by  its  heating  value  in  B.T.U.  This  result, 
divided  by  the  weight  of  the  liquid  taken,  gives  the  B.T.U.  per 
pound  of  the  sample. 

NOTES. — (1)  To  calculate  B.T.U.  per  gallon  determine  the  sp.  gr.  of  the 
liquid  at  15.5°  C.  and  multiply  this  by  8£  *  and  then  by  the  B.T.U.  per  pound. 

(2)  In  case  it  is  found  that  the  calorimetric  value  of  the  liquid  cannot  be 
determined  with  the  liquid  alone,  recently  ignited  asbestos  can  be  used  as  an 
absorbent.     This  method  is  resorted  to  when  the  liquid  explodes  violently 
and  the  determination  is  incomplete,  as  is  shown  by  carbonaceous  residues  in 
the  bomb.     Ignite  the  asbestos  in  a  hot  muffle  for  4  hours  to  insure  the 
removal  of  any  combustible  matter.     Weigh  the  capsule  alone,  fill  with  the 
ignited  asbestos,  and  weigh  again.     Then  fill  the  capsule  with  the  liquid  by 
means  of  a  small  pipette  and  weigh  again  to  obtain  the  weight  of  the  liquid 
taken. 

(3)  Heating  Value  of  Capsules. — The  capsules  after  being  dried  should  be 
kept  in  a  rubber-stoppered  bottle.     The  calorific  value  of  the  dried  capsules 
per  gram  is  obtained  by  weighing  five  capsules  and  burning  them  together  in 
the  bomb.     The  average  result  of  check  determinations  thus  run  is  taken  as 
the  heating  value  per  gram  of  the  capsules.     The  heating  value  of  the  capsule 
used  expressed  in  B.T.U.  is  deducted  from  the  total  number  of  B.T.U.  de- 
veloped in  the  bomb. 

Sulfur. — The  method  of  determining  the  sulfur  content  of 
liquids  from  the  bomb  washings  after  combustion  in  the  bomb  is 
accurate,  practicable  and  rapid,  and  is  recommended  in  preference 
to  all  other  methods. 

The  pressures  given  in  the  section  pertaining  to  the  B.T.U. 
determinations  are  higher  than  is  required  for  the  calorific  deter- 
*  One  gallon  pure  H2O  at  15.5°  C.  weighs  8.3335  Ibs. 


192  TECHNICAL  METHODS  OF  ANALYSIS 

mination  alone  but  by  using  these  amounts  it  has  been  found 
that  the  carbon  and  sulfur  are  completely  burned,  as  no  trace  of 
CO  or  S(>2  were  evident  when  tested  for. 

After  the  regular  calorimetric  determination  has  been  made, 
as  outlined  above,  cool  down  the  bomb  to  tap  water  temperature. 
Then  open  and  wash  the  contents  into  a  beaker  and  titrate.  Add 
5  cc.  of  a  saturated  solution  of  Na2CC>3,  heat  to  boiling  for  ten  min- 
utes and  then  filter  and  wash  6  times  with  hot  distilled  water. 
To  the  filtrate  add  10  cc.  of  saturated  bromine  water,  make 
slightly  acid  with  HC1  and  boil  to  expel  liberated  Br  and  CO2. 
Add  slowly  from  a  pipette  10  cc.  of  a  10%  solution  of  BaCl2  -2H20. 
Continue  the  boiling  for  fifteen  minutes  and  let  stand  overnight 
just  below  the  boiling  point.  Complete  the  sulfur  determination 
as  described  under  Sulfur  in  Coal,  page  175.  Run  a  blank  sulfur 
determination  on  one  of  the  capsules. 

n  T>          j.  a     (weight  of  BaSC>4  —  blank)     1 0  _0 

CALCULATION.— Per  cent  S  =  * — -     .  ,  x    , -, X  13.73. 

weight  ot  sample 

REFERENCES. — Bulletin  43,  Bureau  of  Mines:  "  Comparative  Fuel  Values 
of  Gasoline  and  Denatured  Alcohol  in  Internal  Combustion  Engines." 
Strong  and  Stone,  1912. 

Technical  Paper  26,  Bureau  of  Mines:  "Methods  of  Determining  the 
Sulfur  Content  of  Fuels,  Especially  Petroleum  Products."  Allen  and  Robert- 
son, 1912. 


CHAPTER  VI 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS 


H 

Dia. 


-x 

Dia. 


TURPENTINE 

General. — The  nature  of  a  turpentine  and  whether  or  not  it  is 
adulterated  can  best  be  determined  by  careful  distillation  and 
examination  of  the  various 
fractions  as  to  sp.  gr.,  index  of 
refraction  and  boiling  point. 

Procedure.  -  -  Weigh  500 
grams  of  the  turpentine  into  a 
round-bottom  flask  of  about 
1  liter  capacity.  Connect  the 
flask  by  means  of  a  tightly 
fitting  stopper  to  a  Hempel 
column  of  the  exact  dimen- 
sions shown  in  Fig.  11.  In 
the  top  of  the  Hempel.  column 
place  a  thermometer  with  the 
bulb  reaching  to  within  1  inch 
of  the  glass  beads,  and  connect 
the  side  arm  to  a  condenser. 
Drop  into  the  flask  a  small  flat 
coil  of  copper  or  nickel  wire 
to  prevent  bumping  and 
place  the  flask  and  contents 
on  a  sand  bath.  If  the  room 

temperature    is    very  low,  it  FlG.  n._Hempel  Column, 

may  be  necessary  to  place  a 

shield  of  asbestos  board  around  the  column.  Distill  the  turpen- 
tine at  a  maximum  rate  of  2  drops  per  second.  It  is  important 
that  this  rate  shall  not  be  exceeded.  Collect  the  distillate  in 

193 


3E. 


All  Diameter  Measurements 
are  Inside  Dimeusions 


194  TECHNICAL  METHODS  OF  ANALYSIS 

weighed  flasks  or  cylinders  of  about  100  cc.  capacity.  While  the 
temperature  of  distillation  is  changing  rapidly  the  fractions  col- 
lected should  be  small,  varying  from  4-5%,  and  when  the  tem- 
perature is  slow  and  regular  they  may  be  increased  to  10-12%. 
Usually  it  is  unnecessary  to  continue  the  distillation  after  a  tem- 
perature of  180°  C.  (corrected)  has  been  reached,  unless  there  is  a 
large  amount  of  residue  at  this  stage. 

As  soon  as  a  fraction  has  been  collected,  the  flask  or  cylinder 
in  which  it  is  contained  should  be  immediately  stoppered.  Take 
the  weight  of  each  fraction  and  record  the  temperature  at  which 
the  first  drop  of  the  fraction  distilled.  Also  determine  the  sp.  gr. 
at  15°  C.  and  index  of  refraction  at  15°  C.  of  each  fraction. 

BOILING  POINT. — Correct  the  boiling  temperature  as  actually 
read  on  the  thermometer: 

(1)  For  the  prevailing  barometric  pressure,  by  adding  0.056° 
for   every   mm.    which    the    barometer    reads    below    760    mm. 
and  subtracting  a  corresponding  amount  for  every  mm.  above 
760  mm. 

(2)  For  the  emergent  stem  of  the  thermometer,  according  to 
the  following  formula: 

B.  P.  =  T+0.000143  (T-0  N, 

where  B.  P.  is  the  corrected  boiling  point  sought,  T  is  the  observed 
temperature,  t  is  the  mean  temperature  of  the  thermometer 
stem  above  the  cork  (measured  by  fastening  by  means  of  rubber 
bands  to  the  thermometer  in  the  Hempel  column  another  ther- 
mometer with  its  bulb  at  the  middle  of  the  exposed  thread  of 
mercury),  and  N  is  the  length,  expressed  in  degrees,  of  the  mercury 
column  above  the  cork. 

SPECIFIC  GRAVITY. — Determine  the  sp.  gr.  by  means  of  a  West- 
phal  balance,  making  the  determinations  at  room  temperature 
and  correcting  to  15°  C.  by  using  the  factor  0.00083  for  every 
degree  C.  of  difference  from  this  standard  temperature.  This 
correction  is  to  be .  added  for  temperatures  above  15°  C.  and 
to  be  subtracted  for  temperatures  below  15°  C.  For  small  frac- 
tions the  sp.  gr.  may  be  taken  with  the  Westphal  balance  by  placing 
the  liquid  in  a  test-tube  supported  in  a  flat  cork.  Since  the  cor- 
rection for  temperature  is  large,  take  special  care  to  make  the 
temperature  readings  accurate  when  the  gravity  is  determined. 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS        195 


INDEX  OF  REFRACTION. — Determine  the  index  of  refraction  by 
means  of  the  Abbe  refractometer,  taking  the  readings  at  room 
temperature  and  correcting  by  means  of  the  factor  0.00047  for 
every  degree  of  difference  from  the  standard  temperature  of  15°  C., 
adding  the  correction  for  temperatures  above  15°  C.  and  sub- 
tracting it  for  temperatures  below. 

Recording  Results. — Plot  the  three  curves  for  corrected  boiling 
point,  specific  gravity  and  refractive  index,  respectively,  on  the 
same  sheet  of  paper,  plotting  the  percentage  (by  weight)  of  each 
fraction  vertically  and  the  other  factor  horizontally. 


).56  0.88  0.90  0.92  0.94 
150°  160°  170°  180°  190° 
1.464  1.468  1.472  1476  1,480 


Specific  Gravity 

Boiling  Point 
Index  of  Refraction 


0.86   0.88  0.90  0.92  0.91 
150°  160°    170 c 


°  180°  190°   o 
1164X4681.4721476  1.480  a 

FIG.  12. — Typical  Curves  Showing  Specific  Gravities. 
Boiling  Points  and  Indices  of  Refraction  of: 

A.  Boiling  Gum  Turpentine. 

B.  Wood  Tupentine. 

Interpretation  of  Results.— The  typical  curves  of  pure  gum  and 
wood  turpentines  are  shown  in  Fig.  12.  An  unadulterated  sample 
will  show  curves  which  may  be  slightly  misplaced  to  the  right  or 
left  but  will  be  parallel  to  these  curves.  In  general,  for  a  pure  gum 
turpentine  the  first  fraction  of  the  distillation  should  give  figures 
within  the  following  limits : 

Refractive  index  at  15°  C 1.4700-1.4725 

Sp.  gr.  at  15°  C 0.864-0.866 

Corrected  boiling  point 156-157.5°  C. 


196  TECHNICAL  METHODS  OF  ANALYSIS 

Pure  gum  turpentines  of  which  the  first  fraction  falls  outside 
these  limits  are  rare,  but  if  the  rest  of  the  curve  is  normal  such  a 
turpentine  probably  is  not  adulterated. 

REFERENCE. — U.  S.  Dept.  of  Agriculture,  Forest  Service  Bulletin  105. 

TURPENTINE 
ELECTRIC  RAILWAY  SPECIFICATIONS 

General. — The  material  desired  is  pure  gum  or  refined  steam- 
distilled  turpentine,  free  from  adulteration. 

Requirements. — Turpentine  must  meet  the  following  require- 
ments : 

1.  Appearance. — Clear  and  practically  water-white. 

2.  Specific  Gravity.— Sp.  gr.  at  15.5°  C.  not  less  than  0.862 
nor  more  than  0.872. 

3.  Distillation. — When  200  cc.  are  distilled  as  below  described, 
95%  should  pass  over  below  170°  C. 

Conduct  the  distillation  in  a  300  cc.  flask  8  cm.  in  diameter 
with  the  side  tube  8  cm.  from  the  main  bulb  and  the  neck  extend- 
ing 8  cm.  above  the  side  tube.  The  diameter  of  the  neck  is  2  cm. ; 
of  the  side  tube,  5  mm.  Fit  into  the  stopper  in  the  neck  a 
thermometer  (reading  from  145-200°  C.)  with  the  bulb  opposite 
the  side  tube  of  the  flask  and  the  175°  C.  mark  below  the  stopper. 
Conduct  the  distillation  so  that  about  2  drops'  of  distillate  come 
over  per  second. 

4.  Residue  on  Evaporation. — When  1.0  cc.  of  the  sample  are 
placed  in  a  glass  crystallizing  dish  2.5  inches  diameter  and  1J 
inches  high  and  evaporated  on  the  open  steam  bath  with  a  full 
head  of  steam  for  three  hours,  the  amount  of  residue  shall  not 
weigh  over  0.15  gram.     One  drop  allowed  to  fall  on  a  clean  white 
paper  must  completely  evaporate  at  room  temperature  (20°  C.) 
without  leaving  any  stain. 

5.  Polymerization  Test. — When  5  cc.  of  the  sample  are  treated 
with  cone.  H^SO*  according  to  the  following  method,  not  over  0.50 
cc.  shall  remain  undissolved  at  the  end  of  thirty  minutes.     The 
unpolymerized  residue  shall  be  viscous  in  nature  and  show  a  refrac- 
tive index  between  1.50  and  1.52  at  15.5°  C. 

METHOD. — Add  slowly  5  cc.  of  turpentine  to  25  cc.  of  cone. 
H2S04  in  an  ordinary  graduated  narrow  neck  Babcock  milk  flask 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       197 

(the  smallest  divisions  on  the  neck  of  these  flasks  are  0.04  cc.); 
shake  the  flask  with  a  rotary  motion  to  insure  gradual  mixing, 
keeping  cool,  if  necessary,  in  ice  water  and  not  allowing  the  tem- 
perature to  rise  above  60-65°  C.  .Agitate  thoroughly  and  main- 
tain at  about  65°  C.  with  frequent  agitation  for  one  hour.  Cool 
and  fill  the  flask  with  cone.  H^SCU,  bringing  the  unpolymerized 
residue  into  the  graduated  neck.  Let  stand  one-half  hour  and  read 
off  the  volume  of  unpolymerized  residue.  Note  its  consistency 
and  color  and  determine  its  refractive  index  at  15.5°  C. 

NOTE. — If  the  residue  is  water- white  and  limpid  and  does  not  show  the 
proper  refractive  index,  repolymerize  with  38  N  H2SO4  (100.92%  H^CX  by 
weight,  prepared  by  mixing  cone.  H2SO4  with  sufficient  fuming  H2SO4  to 
give  this  strength)  as  described  by  Veitch  in  U.  S.  Dept.  of  Agriculture, 
Bureau  of  Chemistry,  Bulletin  135,  page  30  (or  Circular  85). 

LINSEED  OIL 

General. — Raw  linseed  oil  is  the  refined  oil  obtained  from  flax- 
seed  or  linseed,  generally  by  hydraulic  pressing.  For  use  in  paint, 
etc.,  to  obtain  quicker  drying  qualities,  raw  oil  may  be  heated 
with  very  small  amounts  of  certain  "  driers  "  such  as  oxides  of 
Pb,  Mn,  Co,  etc.  Oil  thus  prepared  is  called  boiled  linseed  oil. 

Oils  from  different  countries  vary  somewhat  in  composition. 
Pure  linseed  oils  from  North  America  should  show  about  the  fol- 
lowing "  constants  " : 


Raw 


Boiled 


Max. 

Min. 

Max. 

Min. 

Sp.  gr.  at  15.5°  C  
Refractive  index  at  25°  C  .... 

0.938 
1.4805 

0.932 
1.4790 

0.945 

0.935 

Saponification  number  

195 

189 

195 

185 

Iodine  number               .    ... 

180 

160 

Unsaponifiable  matter 

1  50% 

1  50% 

Acid  number  

6.0 

10.0 

Drying  test  

75  hrs. 

24  hrs. 

A  low  iodine  number  accompanied  by  a  high  sp.  gr.  may  indi- 
cate polymerization  due  to  old  age  or  excessive  heating.  High- 
grade  oils  should  also  be  clear  and  free  from  "  foots  "  or  sediment. 


198  TECHNICAL  METHODS  OF  ANALYSIS 

Preparation  of  Sample. — See  page  230. 

Specific  Gravity  at  15.5°  C.— See  page  230. 

Refractive  Index  at  25°  C.— See  page  231. 

Saponification  Number. — S.ee  page  241. 

Iodine  Number. — See  page  241. 

Unsaponifiable  Matter. — Use  Boemer's  Method  (page  262). 

Acid  Number.— See  page  242. 

Drying  Test. — Flow  some  of  the  sample  over  a  piece  of  clean 
glass  and  let  drain  in  a  vertical  position  at  about  20°  C.,  testing 
at  intervals  for  "  tackiness  "  with  the  finger.  Note  how  long  it 
requires  for  the  film  to  become  dry. 

TUNG  OIL 

General. — This  oil  is  also  known  under  various  other  names 
such  as  "  China  Wood  Oil,"  "  Japanese  Wood  Oil,"  "Wood 
Oil,"  or  "  Nut  Oil."  It  has  a  strong  characteristic  odor.  Most 
of  it  comes  from  China;  a  small  amount  comes  from  Japan. 

Cold  drawn  oil  is  pale  yellow  and  called  "  White  Tung  Oil"; 
hot  pressed  oil  is  dark  brown  and  called  "  Black  Tung  Oil."  Very 
little  of  the  latter  comes  to  this  country. 

The  constants  of  pure  Chinese  oil  are  as  follows: 

Sp.  gr.  at  15.5°  C 0.939-0.943 

Saponification  number 190-200 

Iodine  number 150-166 

Refractive  index  at  25°  C 1.515-1.520 

Heating  test  (Browne  method) max.  12  minutes 

Iodine  jelly  test max.    4  minutes 

Japanese  oil  has  a  lower  sp.  gr.  (about  0.933-0.935  at  15.5°  C.) 
For  further  properties,  see  Lewkowitsch:    "  Chemical  Tech- 
nology and  Analysis  of  Oils,  Fats  and  Waxes,"  Vol.  II. 
Specific  Gravity  at  15.5°  C.— See  page  230. 
Saponification  Number. — See  page  241. 
Iodine  Number. — See  page  241. 
Free  Fatty  Acids.— See  page  242. 
Refractive  Index  at  25°  C.— See  page  231. 
Unsaponifiable  Matter.— See  page  262. 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       199 

Heating  Test  (Browne  Method).— Place  in  a  160X15  mm.  test 
tube  5  cc.  of  water  and  make  a  mark  at  the  5  cc.  point.  Then  dry 
the  test  tube  and  insert  a  cork  perforated  so  that  a  glass  rod  of  3 
mm.  diameter  can  move  freely.  Fill  a  copper  dish  12  cm.  high  by 
6  cm.  inside  diameter  with  cottonseed  oil  to  a  height  of  7.5  cm. 
Insert  a  thermometer  so  that  the  bulb  is  1.5  cm.  from  the  bottom 
of  the  dish. 

The  thermometer  should  be  nitrogen-filled,  total  immersion, 
length  4-^.5  inches,  graduated  from  210-310°  C.  in  2°  intervals; 
length  between  210  and  310°  C.  not  less  than  2.5  inches.  If  pre- 
ferred, a  longer  thermometer  (30  cm.  with  graduations  from  100- 
400°  C.)  may  be  used,  in  which  case  make  corrections  for  the 
emergent  stem.  (See  U.  S.  Bureau  of  Standards,  Stem  Correction 
Sheet  No.  44.) 

Heat  the  bath  slowly  to  293°  C.;  then  place  in  it  the  tube 
containing  5  cc.  of  the  oil  sample,  so  that  the  bottom  is  level  with 
the  lowest  part  of  the  thermometer  bulb.  Note  the  time  and 
remove  the  heat  for  about  forty-five  seconds;  then  re-apply  the 
heat.  Before  two  minutes  have  elapsed,  the  temperature  of  the  bath 
will  have  fallen  to  282°  C.  Hold  at  this  point  as  steadily  as  pos- 
sible. When  the  sample  has  been  in  the  bath  about  nine  minutes, 
raise  the  glass  rod  at  intervals  of  one-half  minute  and  when  the 
rod  is  firmly  set,  note  the  time.  Remove  the  flask  at  once;  heat 
the  bath  again  to  293°  C.  and  repeat  the  experiments  with  another 
portion  of  the  sample. 

No  stirrer  is  necessary  in  the  bath,  but  it  should  be  protected 
with  a  screen.  When  the  cottonseed  oil  bath  becomes  tarry 
and  viscid,  it  should  be  renewed. 

Pure  tung  oil  should  "  set  "  within  twelve  minutes. 

Iodine  Jelly  Test. — Weigh  accurately  2.500  grams  of  sample 
into  a  wide-necked  200  cc.  Erlenmeyer  flask;  add  10  cc.  of  CHCla 
from  a  pipette  and  stopper  the  flask  immediately.  Carefully 
insert  into  the  flask  a  small  glass  vial  so  that  it  stands  upright,  and 
into  this  vial  pipette  10  cc.  of  a  solution  of  iodine  in  CHCls  con- 
taining 0.035-0.036  gram  of  iodine  per  cc.  Place  the  flask  in  a 
bath  containing  water  at  25-26°  C.  and  let  stand  a  few  minutes, 
keeping  the  flask  stoppered  except  when  necessary  to  remove  it. 

Tilt  the  flask  and  rotate  so  that  the  vial  is  upset  and  the  con- 
tents are  thoroughly  mixed,  starting  a  stop  watch  at  the  same 


200  TECHNICAL  METHODS  OF  ANALYSIS 

time.  Keep  the  flask  in  the  bath  at  25-26°  C.,  and  every  fifteen 
seconds  tilt  the  flask  toward  a  horizontal  position.  Note  the  time 
required  for  formation  of  a  jelly  that  does  not  flow  but  sticks  to 
the  bottom  of  the  flask  or  slides  in  a  mass.  Record  the  time  to  the 
nearest  quarter  minute.  Pure  tung  oil  should  require  2.75-3.25 
minutes  to  jell. 

If  the  temperature  of  the  laboratory  varies  more  than  2  or  3°  C. 
from  25°  C.,  place  the  flask  containing  the  iodine  solution  in  the 
bath  and  let  it  remain  for  several  minutes  before  pipetting  out  the 
10  cc.  for  test. 

The  CHC13  used  to  dissolve  the  oil  and  to  prepare  the  iodine 
solution  should  conform  to  U.  S.  P.  requirements  and  have  a  sp.  gr. 
of  1.480-1.481  at  25°  C.  If  the  sp.  gr.  is  too  low,  wash  the  CHC13 
with  water;  if  too  high,  add  a  little  95%  grain  alcohol. 

The  iodine  solution  is  prepared  as  follows:  Treat  an  excess  of 
iodine  with  warm  CHCls;  shake  for  a  few  minutes;  cool  to 
about  20°  C.  and  filter  through  glass  wool.  Pipette  10  cc.  of  the 
solution  into  an  Erlenmeyer  flask  containing  10  cc.  of  10%  KI 
solution  and  titrate  with  0.1  N  thiosulfate.  Calculate  the  iodine 
content  and  dilute  with  CHCls  so  as  to  obtain  an  iodine  content 
of  0.035-0.036  gram  per  cc.  After  dilution,  titrate  again  to  make 
sure  the  solution  is  of  proper  strength. 

The  above  method  is  empirical  and  details  must  be  followed 
exactly. 

REFERENCES. — Lewkowitsch :,  "Chemical  Technology  and  Analysis  of 
Oils,  Fats  and  Waxes,"  Vol.  II;  American  Society  for  Testing  Materials, 
Standard,  Serial  D-12-16. 

MIXED  PAINTS  AND  PIGMENTS  IN  OIL 

General. — Paints  from  the  chemical  point  of  view  may  be  con- 
sidered as  consisting  of  two  parts,  (1)  the  vehicle,  and  (2)  the  pig- 
ment. 

The  vehicle  may  consist  entirely  of  linseed  oil,  which  is  usually 
the  case  with  individual  paste  pigments.  Frequently,  however, 
especially  in  the  case  of  mixed  paints,  it  also  contains  a  certain 
amount  of  driers  and  of  thinner  (either  turpentine  or  mineral 
spirits) ;  and  in  the  case  of  enamels  and  high  gloss  paints,  the  vehicle 
may  also  contain  varnish  or  varnish  gums. 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       201 

The  pigment  may  be  a  simple  chemical  compound,  such  as 
ZnO,  or  a  mixture  of  several  substances.  Zinc  oxide,  basic  car- 
bonate white  lead,  and  basic  sulfate  white  lead,  are  among  the 
most  important  ingredients  of  paint  pigments.  Red  lead  and 
graphite  are  largely  used  as  protective  coatings  for  iron  and  steel. 
Numerous  other  substances  are  also  used  as  paint  pigments,  many 
of  which  are  by  no  means  simple  chemical  compounds,  such  as 
mineral  silicates,  yellow  ochre,  umber,  lithopone,  etc. 
The  most  important  paint  pigments  are  the  following : 
WHITE  PIGMENTS. — 1.  Basic  Carbonate  White  Lead  is  approx- 
imately 2PbC03-Pb(OH)2. 

2.  Basic  Sulfate  White  Lead  is  largely  basic  lead  sulfate,  often 
containing  a  little  ZnO. 

3.  Zinc  Oxide  (Zinc  White),  ZnO. 

4.  Lithopone  is  made  by  simultaneous  precipitation  of  ZnS 
and  BaS04  and  generally  contains  about  70%  of  the  latter. 

5.  Barytes  or  Blanc  Fixe  is  BaS04. 

6.  Silica  (Silex).    This  may  be  ground  silica  or  diatomaceous 
(infusorial)  earth. 

7.  Asbestine  is  essentially  a  silicate  of  Mg  and  is  made  by 
grinding  waste  asbestos. 

8.  Clay  ( Kaolin)  is  a  hydrated  aluminum  silicate. 

9.  Gypsum  (Terra  Alba)  is  CaSO4-2H20.     Anhydrous  CaSO4, 
or  burnt  gypsum,  is  used  as  an  extender  in  Venetian  Red. 

10.  Chalk,  Paris  White,  Whiting,  Alba  Whiting,  etc.     These 
are  all  CaCOa  but  differ  somewhat  in  their  physical  conditions. 

BLACK    PIGMENTS. — 1.  Lampblack   is  a  grayish   black,  bulky 
pigment.     It  is  the  soot  produced  by  burning  oils,  resins,  etc. 

2.  Gas  Black  (Carbon  Black)  is  made  from  natural  gas.     It  is 
much  blacker  than  lampblack. 

3.  Bone  Black  is  made  by  carbonizing  bones.     It  contains 
10-20%  carbon,  the  remainder  being  largely  calcium  phosphate. 

4.  Ivory  Black  (Dro^  Black)  is  a  high-grade  bone  black  made 
from  ivory  waste. 

NOTE. — The  color  of  bone  black  and  ivory  black  may  be  modified  by  the 
addition  of  Prussian  blue. 

5.  Charcoal  Black  is  produced  from  vegetable  charcoal. 

6.  Graphite  (Plumbago)  is  a  form  of  carbon  occurring  as  a 


202  TECHNICAL  METHODS  OF  ANALYSIS 

natural  mineral.     That  used  in  paints  may  run  up  to  85%  carbon, 
the  remainder  being  silicious  matter. 

RED  PIGMENTS — 1.  Indian    Red   is    essentially   Fe20s — dark 
purplish  red. 

2.  Tuscan  Red  is  Indian    red  enriched  by  an  alizarin  lake, 
giving  a  crimson  shade.     It  is  often  toned  down  with  BaSCU, 
CaCOs,  or  gypsum. 

3.  Venetian  Red  is  also  largely  Fe20s,  but  is  brick  red  in  color 
and  contains  more  or  less  gypsum  (or,  in  inferior  grades,  CaCOs 
or  BaS04). 

4.  Red  Lead  is  a  brilliant  scarlet  but  is  used  as  a  protective 
coating  and   not  as  a  tinting   pigment.     When  c.  P.  it  is  PbsOi 
but  the  commercial  product  contains  70-99%  PbsC^   (usually 
over  85%),  the  remainder  being  PbO  incidental  to  manufacture, 
unless  the  material  is  intentionally  adulterated. 

5.  Orange  Mineral  is  a  form  of  red  lead  with  a  lower  sp.  gr.  and 
lighter  color  than  the  usual  form. 

6.  English    Vermilion   is   HgS.     It   is   not   much   used   now 
because  of  its  high  price. 

7.  American  Vermilion  (Chrome  Red,  Scarlet  Lead  Chr ornate) 
is  a  basic  chromate  of  lead. 

8.  Lakes  are  formed  by  combining  the  coloring  matter  of  cer- 
tain dyes  with  inorganic  carriers,  such  as  BaSCX,  CaCOs  or  clay. 
They  are  generally  used  in  paints  with  a  large  amount  of  other 
pigment  for  brightening  or  modifying  the  color.     Among  the  most 
important  lakes  are  the  vermilions  and  scarlets  made  from  para- 
red,  and  from  alizarin.     The  dye  (color)  may  be  as  little  as  5% 
in  the  lake  itself. 

YELLOW  PIGMENTS. — 1.  Chrome  Yellows  are  chromates  of  lead 
of  varying  color  and  composition. 

(a)  Chrome     Yellow     Light    ("  Chrome    Yellow     Lemon "     or 
"  Canary  ")  contains  more  or  less  PbSCX  or  other   insoluble  Pb 
compound  intimately  mixed  with  PbCrO4. 

(b)  Chrome  Yellow  Medium  is  pure  PbCrCU. 

(c)  Chrome   Yellow  Orange   (Chrome  Orange)   is    a  basic  lead 
chromate  which  may  vary  in  color  from   pale  orange  to  nearly 
scarlet. 

2.  Ochers  (Yellow  Ochers)  are  natural  .earths  whose  color  is 
due   to   hydrated   iron   oxide    (limonite,    2Fe(OH)3-Fe2Os)    and 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       203 

varies  from  citron  yellow  to  almost  olive.  The  hydrated  iron 
oxide  may  vary  from  10-60%,  the  remainder  being  silicious 
matter  or  clay.  Golden  Ocher  is  yellow  ocher  modified  with 
PbCrO4. 

3.  Raw  Siennas  resemble  ochers  in  general  composition,  but 
are  brownish  yellow  and  generally  contain  a  little  manganese. 

BROWN  PIGMENTS. — 1.  Burnt  Sienna  is  made  by  calcining 
raw  sienna,  which  changes  the  color  to  an  orange  red  or  red  brown. 

2.  Raw  Umber  is  a  natural   earth  pigment  of  yellow-brown 
color  inclining  towards  the  olive  and  is  similar  in  composition  to 
sienna  but  contains  considerable  manganese  oxide. 

3.  Burnt  Umber,  made  by  calcining  raw  umber,  has  a  rich 
brown  color,  darker  than  the  raw  but  free  from  red. 

4.  Vandyke  Brown  (Cassel  Earth,  Cologne  Earth)  is  a  natural 
pigment  of  a  carbonaceous  nature  and  is  distinguished  by  its  sol- 
ubility in  dil.  alkali. 

BLUE  PIGMENTS. — 1.  Prussian  Blue  is  made  by  precipitating 
a  soluble  ferrocyanide  with  FeSCX  and  oxidizing  the  precipitate. 
If  the  precipitate  were  pure  and  completely  oxidized  it  would,  of 
course,  have  the  composition  Fe4[Fe(CN)6]3.  The  commercial 
product,  however,  varies  considerably  in  composition. 

2.  Ultramarine  was  formerly  obtained  from  the  semi-precious 
mineral  lapis  lazuli.     It  is  now  made  artificially,  however,  and  is 
quite  cheap.     It  is  essentially  a  double  silicate  of  Al  and  Na  with 
some  sulfides  or  sulfates.     It  yields  EkS  when  treated  with  HC1 
and  loses  its  color  even  with  weak  acids. 

3.  Cobalt   Blue  consists  of  oxides  of  Al  and   Co.     Genuine 
cobalt  blue  is  quite  expensive  and  it  is  frequently  substituted  by 
ultramarine  mixed  with  a  little  ZnO. 

GREEN  PIGMENTS. — 1.  Chrome  Green  is  an  intimate  mixture 
of  Prussian  blue  and  chrome  yellow  and  in  this  form  is  sold  as 
"  chemically  pure."  It  is  also  put  out  as  "  commercial  chrome 
green"  which  generally  contains  about  25%  of  the  pure  color 
and  75%  of  BaS(>4  or  a  silicate. 

2.  Chrome  Oxide  Green  is  C^Oa,  often  more  or  less  hydrated. 
It  is  an  expensive  pigment. 


204  TECHNICAL  METHODS  OF  ANALYSIS 


ANALYSIS 

It  is  impossible  to  outline  a  general  method  which  will  be 
applicable  to  all  paints.  The  following  procedures  for  the  separa- 
tion and  determination  of  the  amount  of  vehicle  and  pigment, 
however,  are  applicable  to  most  paints  and  to  pigments  ground  in 
oil. 

Total  Vehicle. — The  vehicle  may  be  separated  from  the  pig- 
ment either  by  continuous  extraction  or  by  dilution  with  a  suitable 
solvent  and  whizzing  in  a  centrifuge. 

(A)  BY  CONTINUOUS  EXTRACTION. — Mix  the  sample  very  thor- 
oughly [see  note  (1)  below],  taking  particular  pains  to  stir  up  any 
pigment  which  has  settled.     Partly  fill  a  small  beaker  with  the 
well-mixed  paint  and  place  in  it  a  stirring  rod.     Insert  a  plug  of 
cotton  in  a  Soxhlet  extraction  thimble  (of  double  thickness  if  the 
paint  contains  ZnO  or  other  extremely  fine  pigments),  dry  at  100° 
C.  and  weigh.     Stand  the  thimble  in  another  small  beaker,  and 
remove  the  cotton.     Weigh  the  beaker  with  the  paint,  then  fill  the 
thimble  about  three-quarters  full,   pouring  the  paint  carefully 
down  the  stirring  rod.     Again  weigh  the  beaker  with  the  stirring 
rod  and  determine  the  amount  of  paint  which  has  been  transferred 
to  the  thimble.     Plug  the  thimble  lightly  with  the  cotton,  place  it 
in  a  Soxhlet  extractor,  fill  the  extractor  nearly  full  of  ether  and  let 
the  paint  and  the  thimble  soak  in  it  for  at  least  one  hour  before 
starting  the  siphoning.     Continue  the  extraction  until  the  ether 
extract  comes  over  colorless.     Then  remove  the  thimble,  let  the 
pigment  dry,  grind  it  to  break  up  lumps,  return  to  the  thimble  and 
again  extract  for   at  least  four   hours  (or  overnight).     Finally 
evaporate  the  ether  from  the  extract  and  dry  to  constant  weight 
at  105-110°  C.     Also  dry  the  thimble  with  the  pigment  at  about 
105°  C.  and  weigh  it.     The  difference  between  100%  and  the  sum 
of  the  percentages  of  the  pigment  and  of  the  ether  extract  is  a 
rough  indication  of  the  amount  of  volatile  thinner.     In  case  only 
the  total  pigment  and  total  vehicle  are  desired,  the  weight  of  the 
dried  pigment  and  not  of  the  extract  should  be  used  in  making  the 
calculations. 

(B)  BY  CENTRIFUGING.— Weigh  2  empty  cylinders  (4  oz.  oil 
sample  bottles  are  convenient),  fill  each  about  one-quarter  to  one- 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       205 

third  full  of  the  mixed  paint,  and  again  weigh.  Add  an  equal 
volume  of  ether,  mix  thoroughly,  place  the  cylinders  in  a  cen- 
trifuge opposite  each  other,  so  that  they  counterbalance,  and 
whiz  until  the  pigment  settles  clear.  Pour  off  or  siphon  off  as 
much  as  possible  of  the  clear  liquid,  refill  the  cylinders  with  ether, 
stir  up  the  pigment  and  again  centrifuge.  Repeat  the  process 
until  the  pigment  is  free  from  oil.  Remove  the  ether  with  a  gentle 
air  blast  and  dry  the  pigment  to  constant  weight  at  105°  C. 

NOTES. — (1)  If  the  sample  is  a  large  one,  received  in  the  original  can, 
weigh  the  can  as  a  whole,  without  shaking,  remove  as  much  of  the  clear 
vehicle  as  possible,  and  transfer  it  to  a  cork-stoppered  flask  or  bottle.  Weigh 
the  can  to  obtain  the  amount  of  vehicle  removed.  Then  mix  thoroughly  the 
contents  of  the  can  and  transfer  to  another  container.  Clean  out  the  empty 
can  and  weigh  it.  From  these  figures  the  analytical  results  can  be  calculated 
back  to  the  original  material. 

(2)  The  method  of  centrifuging  is  more  rapid  than  the  continuous  extrac- 
tion method  and  in  the  case  of  very  fine  pigment  which  cannot  be  held  by  the 
thimbles  it  is  preferable. 

(3)  In  many  cases  it  is  preferable  to  use  several  solvents  in  sequence  as 
follows:  Extract  with  gasoline  by  means  of  the  centrifuge,  again  extract  with 
gasoline,  then  with  benzene,  and  finally  with  ether,  removing  each  time  as 
much  as  possible  of  the  clear  extract.     In  the  case  of  certain  enamel  paints, 
it  is  advisable  to  follow  the  gasoline  treatment  by  a  treatment  with  turpentine 
and  then  remove  the  turpentine  with  gasoline  before  treatment  with  benzene 
and  ether. 

(4)  In  the  case  of  paints  which  settle  with  difficulty,  better  results  are  some- 
times obtained  by  a  mixture  of  solvents,  such  as  a  mixture  of  6  parts  of  ben- 
zene and  4  parts  of  wood  alcohol  by  volume. 

(5)  No  extraction  process  will  remove  the  last  traces  of  the  vehicle.     The 
insoluble  portion  is  probably  oxidized  linseed  oil  or  metallic  soaps. 

Pigment. — Grind  the  dried  pigment  finely  and  make  a  quali- 
tative analysis  on  a  portion  of  it  before  attempting  a  quan- 
titative analysis.  The  general  procedure  for  a  quantitative 
analysis  of  a  mixed  pigment  is  indicated  on  page  207,  but  the  pro- 
cedure may  have  to  be  considerably  varied  in  individual  cases. 
(See  also  methods  for  White  Lead,  Chrome  Yellow,  and  Red  Lead.) 

Vehicle. — If  the  amount  and  condition  of  the  sample  will  per- 
mit, make  the  analysis  on  the  clear  vehicle  poured  off  from  the 
original  sample. 

(A)  THINNER. — Weigh  50-100  grams  of  the  separated  vehicle 
(or  a  correspondingly  greater  amount  of  the  original  paint)  into 


206  TECHNICAL  METHODS  OF  ANALYSIS 

a  500  cc.  flask  connected  with  a  spray  trap  and  a  vertical  con- 
denser and  distill  with  steam.*  Heat  the  flask  in  an  oil  bath  nearly 
to  100°  C.  before  passing  in  the  steam  and  then  raise  the  tem- 
perature to  130°  C.  Collect  the  distillate  in  100  cc.  graduated 
glass-stoppered  cylinders  which  have  previously  been  weighed. 
When  the  distillate  comes  over  clear,  or  at  least  300  cc.  of  water 
have  been  collected,  stopper  the  cylinders  and  weigh  them.  Read 
the  volume  of  water  and  of  thinner,  subtract  the  weight  of  water 
(1  cc.  of  water  =1  gram)  and  calculate  the  per  cent  of  thinner, 
both  by  volume  and  by  weight  in  the  vehicle,  and  by  weight  in  the 
original  paint. 

Instead  of  collecting  the  distillate  in  graduated  cylinders, 
the  entire  distillate  may  be  collected  in  a  small  weighed  separatory 
funnel.  Then  let  the  layers  separate  sharply,  draw  off  the  water 
and  weigh  the  funnel  containing  the  thinner. 

Determine  the  sp.  gr.  of  the  thinner  at  15.5°  C.  and  make 
a  polymerization  test  and  such  other  tests  as  will  establish  whether 
it  is  pure  turpentine  or  a  mixture  of  turpentine  with  mineral  spirits. 
(See  pages  193  and  196.) 

(B)  ANALYSIS  OF  OIL. — (1)  Specific  Gravity. — Determine  the 
sp.  gr  at  15.5°  C.  of  the  original  vehicle  with  a  hydrometer  or 
Westphal  balance  and  correct  for  the  amount  of  thinner  and  its 
sp.  gr.  as  above  determined. 

(2)  Ash  and  Driers. — Determine  the  amount  of  ash  in  a  por- 
celain crucible  and  its  nature.     If  much  Pb  is  present,  part  of  it  is 
lost  in  igniting  to  ash,  and  a  quantitative  analysis  of  the  ash  is 
therefore  not  accurate.     For  the  quantitative  determination  of 
driers,  see  page  221. 

(3)  Iodine  Number. — Determine  the  iodine  number  of  the  oil 
freed  from  water  after  the  steam  distillation,  bearing  in  mind  that 
the  constants  of  linseed  oil  which  has  been  mixed  with  pigment, 
especially  Pb   compounds,   may  be  much  altered  and  that  an 
iodine  number  even  as  low  as  100  is  not  an  indication  of  the 
presence  of  other  fatty  oils.     (See  page  241.) 

(4)  Mineral  Oil. — Determine    the   saponification    number    as 
described  on  page  241,  and  if  the  oil  is  not  completely  saponifiable, 
determine  the  amount  of  unsaponifiable  oil.     (See  page  261.) 

*  If  alcohol,  acetone  or  other  water-soluble  solvent  is  present,  it  is  neces- 
sary in  order  to  determine  these  to  run  an  additional  distillation  without  steam. 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       207 

Water. — Some  specifications  place  a  maximum  limit  on  the 
permissible  amount  of  water.  The  latter  may  be  determined  on 
the  mixed  paint  by  the  Xylol  Method  as  described  on  page  271, 
using  about  100  grams  of  the  sample. 

REFERENCE. — Holley  and  Ladd:  "  Mixed  Paints,  Color  Pigments  and  Var- 
nishes"; U.  S.  Dept.  of  Agriculture,  Bur.  of  Chem.,  Bulletin  109,  revised; 
Bureau  of  Standards,  Circular  69. 


GREEN  GRAPHITE  POLE  PAINT 

General.  —  This  method  covers  the  analysis  of  Green  Graphite 
Pole  Paint  delivered  under  specifications  requiring  a  paint  con- 
taining between  40  and  45%  of  pigment;  the  pigment  to  consist 
of  amorphous  graphite,  silica,  iron  oxide  and  alumina,  and  tinting 
color,  the  latter  composed  of  Prussian  blue  and  chrome  yellow. 

NOTE.  —  Chrome  yellows  and  chrome  greens  are  sometimes  toned  down  with 
PbSO4  and  barytes  (BaSO4).  Small  amounts  of  these  substances,  therefore, 
would  not  be  cause  for  rejection. 

Pigment  and  Vehicle.  —  Determine  the  proportions  of  pigment 
and  vehicle  by  extracting  a  weighed  quantity  of  the  paint 
with  ether  or  with  low-boiling  gasoline,  either  in  a  Soxhlet  ex- 
tractor *  or  with  a  centrifuge.  Weigh  the  dry  pigment. 

Total  Insoluble  Matter.  —  Boil  1  gram  of  the  dry  pigment  in  a 
250  cc.  beaker  with  30  cc.  of  cone.  HC1  for  about  thirty  minutes. 
Add  from  time  to  time  a  drop  of  alcohol.  Then  add  50  ce.  of 
water  and  boil  again  for  fifteen  minutes.  Filter  on  a  filter  paper 
which  has  been  dried  and  weighed  in  a  weighing  bottle.  Wash 
the  residue  thoroughly  with  hot  water;  dry  in  the  weighing  bottle, 
cool  in  a  desiccator,  and  weigh. 

Carbon.  —  Ignite  the  above  residue  in  a  platinum  crucible  until 
all  C  is  burned  off,  cool  in  a  desiccator  and  weigh.  Report  the 
loss  as  carbon. 

Barium  Sulfate.  —  Moisten  the  residue  in  the  crucible  with  a 
little  water  and  add  a  few  drops  of  dil.  H2SO4.  Then  fill  the 
crucible  two-thirds  full  of  HF.  Evaporate  this  off  on  a  hot 
plate  and  repeat  the  operation  to  insure  removal  of  all 


*  If  an  extractor  is  used,  extract  until  siphonings  are  colorless,  remove  the 
pigment,  dry,  grind  and  re-extract  for  at  least  four  hours. 


208  TECHNICAL  METHODS  OF  ANALYSIS 

Ignite  the  residue  gently  until  all  80s  has  been  driven  off.  Fuse 
this  residue  (consisting  of  Fe2O3,  Al2Os  and  BaSO4)  with  a  con- 
siderable excess  of  KHSCU,  using  a  very  low  flame  to  avoid  sput- 
tering. Digest  the  fusion  in  water  containing  a  little  HC1.  If 
completely  soluble,  no  BaSO4  is  present.  If  there  is  any  residue, 
filter,  wash  with  hot  water,  ignite  in  a  platinum  crucible,  and  weigh 
as  BaS04. 

NOTES. — (1)  The  presence  of  BaSO4  should  be  confirmed  by  fusing  this 
residue  with  Na^COs,  boiling  with  water  and  filtering.  Test  the  filtrate  for 
SO4;  dissolve  the  residue  in  HC1  and  test  for  Ba. 

(2)  Save  the  filtrate  from  the  KHSO4  fusion  for  determination  of  insoluble 
iron  and  alumina. 

Total  Lead.— To  the  filtrate  from  the  total  insoluble,  add 
NH40H  until  a  precipitate  begins  to  form  and  then  just  enough 
HC1  to  redissolve  it.  Dilute  to  about  500  cc.;  saturate  with 
H2S,  heat  to  boiling,  let  settle,  and  filter  off  the  black  PbS.  Wash 
with  H2S  water;  then  dissolve  in  cone.  HNOs,  containing  a  little 
Br  water.  Filter  out  any  sulfur,  boil  off  bromine,  dilute  to  about 
200  cc.,  and  make  faintly  alkaline  with  NIIiOH.  Then  add  a 
slight  excess  of  acetic  acid.  To  the  boiling  solution  add  an  excess 
of  K2Cr2O7  solution.  Boil  for  two  or  three  minutes  until  the  pre- 
cipitate settles  clear.  Filter  on  a  weighed  Gooch  crucible,  wash 
with  hot  water,  dry  at  110°  C.,  set  the  Gooch  crucible  in  a  larger 
platinum  crucible,  ignite  gently,  cool  in  a  desiccator  and  weigh 
as  PbCr04. 

NOTE. — Pb  may  be  also  determined  as  PbSO4  as  described  under  Total 
Lead  in  Chrome  Yellow,  page  214. 

Lead  Chromate. — Boil  the  filtrate  from  the  PbS  until  it  con- 
tains no  more  H2S,  then  add  a  few  drops  of  HNOs  and  boil  again. 
Precipitate  the  hydroxides  of  Fe,  Cr,  and  Al  with  a  slight  excess 
of  NH4OH.  Filter  and  wash  with  hot  water.  Dissolve  in  HC1 
and  make  up  to  250  cc.  Pipette  100  cc.  of  this  solution  (equiva- 
lent to  0.4  gram  of  original  pigment)  into  a  beaker,  add  a  slight 
excess  of  NH4OH,  cool  and  add  about  1  gram  of  Na202,  keeping 
the  beaker  covered  with  a  watch  glass.  Digest  on  the  steam  bath 
until  evolution  of  gas  has  ceased;  filter  and  wash  with  hot  water. 
Redissolve  the  precipitate  in  HC1  and  reprecipitate  with  NH^OH; 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       209 

and  again  add  Na2C>2,  keeping  the  volume  of  solution  small. 
Filter  and  wash.  Combine  both  filtrates  and  make  slightly  acid 
with  acetic  acid  and  boil  until  all  peroxide  has  been  decomposed. 
Continue  the  determination  as  described  under  Lead  Chromate 
in  Chrome  Yellow,  using  either  the  gravimetric  or  the  volumetric 
method  (see  page  215). 

Iron  Oxide  and  Alumina. — Insoluble  Fe2O3  and  A12O3  are 
determined  in  the  solution  of  the  KHS04  fusion  after  filtering  out 
any  BaSO"4  or  undecomposed  silica.  To  this  filtrate  add  a  few 
drops  of  HNOs,  heat  to  boiling  and  then  add  a  slight  excess  of 
NILtOH  and  boil  until  the  odor  of  the  latter  is  nearly  gone.  Filter, 
wash  with  hot  water,  ignite  strongly  and  weigh  as  Fe203+Al203. 

Soluble  Fe203  and  AbOs  are  determined  on  an  aliquot  of  the 
filtrate  from  PbS.  Pipette  100  cc.  (which  is  equivalent  to  0.4 
gram  of  original  pigment)  into  a  beaker,  add  a  few  drops  of  HNOs 
and  heat  to  boiling;  precipitate  with  a  slight  excess  of  NH4OH; 
filter,  wash  with  hot  water,  ignite  over  a  blast  lamp  and  weigh. 
The  residue  consists  of  Fe203+Al203+Cr203.  Subtract  from 
this  the  Cr2O3  equivalent  to  the  PbCrO4  found.  Add  the 
difference  to  the  insoluble  iron  oxide  and  alumina  and  report  as 
total  iron  oxide  and  alumina. 

CALCULATION.— PbCr04X  0.2352  =  Cr203. 

Silica. — Si02  is  obtained  by  calculation  as  follows :  The  residue 
in  the  crucible  after  burning  off  carbon  consists  of  SiO2+BaS04 
(if  present)  +  insoluble  Fe2C>3  and  A^Os.  From  its  weight, 
therefore,  subtract  the  amount  of  other  substances  as  determined 
above  and  report  the  difference  as  silica. 

Prussian  Blue. — Weigh  2  grams  of  dry  pigment  into  a  Kjeldahl 
flask,  and  add  10  grams  of  K2SO4  or  7.5  grams  of  anhydrous  Na2S04 
(free  from  N)  and  30  cc.  of  cone.  H2SO4.  Heat  over  a  Tirrill 
burner,  gently  at  first,  and  then  to  copious  fumes  for  six  to  eight 
hours.  Cool,  dilute  to  about  250  cc.  and  add  a  few  grains  of 
granulated  Zn  and  about  80  cc.  of  cone.  NaOH  solution.*  Distill 
into  50  cc.  of  0.1  N  HC1  until  at  least  100  cc.  have  come  over. 
Titrate  the  excess  of  acid  with  0.1  N  alkali.  Calculate  the  acid 
consumed  to  Prussian  blue,  Fe4[Fe(CN)e]3. 

*  Sufficient  NaOH  solution  must  be  added  to  give  a  strong  alkaline  reac- 
tion after  distillation  is  completed.  See  under  determination  of  Nitrogen, 
page  65. 


210  TECHNICAL  METHODS  OF  ANALYSIS 

CALCULATION. — 1  cc.  0.1  N  acid  =  0.004773  gram  Prussian 
blue. 

NOTES. — (1)  Any  excess  of  Pb  beyond  that  required  for  lead  chromate 
should  be  calculated  to  lead  sulfate. 

PbOO4  X  0.9383  =  PbSO4. 

(2)  Commercial  Prussian  blues  seldom  if  ever  conform  strictly  to  the 
formula  Fe4[Fe(CN)6]3,  but  it  is  necessary  to  assume  some  formula  in  making 
the  chemical  calculation  and  the  theoretical  formula  is  the  one  usually  taken. 

RED  LEAD  AND  ORANGE  MINERAL 

General. — Red  lead  and  orange  mineral  in  the  pure  state  are 
oxides  of  lead  (approximately  PbsOi),  being  probably  mixtures  of 
compounds  containing  varying  proportions  of  PbO  and  Pb02. 

Red  Lead  (Pb3O4). — Weigh  1  gram  of  the  very  finely  ground 
pigment  into  a  150  cc.  Erlenmeyer  flask.  Mix  in  a  small  beaker 
30  grams  of  crystallized  sodium  acetate,  2.4  grams  of  KI,  10  cc.  of 
water  and  10  cc.  of  50%  acetic  acid.  Stir  until  all  is  liquid,  pour 
into  the  Erlenmeyer  flask  containing  the  red  lead,  and  rub  with  a 
glass  rod  until  all  of  the  lead  is  dissolved;  add  30  cc.  of  water,  and 
titrate  with  0.1  N  sodium  thiosulfate,  using  starch  as  indicator. 
A  small  amount  of  lead  may  escape  solution  at  first,  but  when  the 
titration  is  nearly  complete  this  may  be  dissolved  by  stirring.  The 
reagents  should  be  mixed  in  the  order  given,  and  the  titration 
should  be  carried  out  as  soon  as  the  lead  is  in  solution,  as  otherwise 
there  is  danger  of  loss  of  iodine. 

CALCULATION.— 1  cc.  0.1  N  thiosulfate  =  0.03428  gram  Pb3O4. 

For  purpose  of  calculation  it  may  also  be  assumed  that  1  cc. 
0.1  N  thiosulfate  =  0.03348  gram  PbO.  This  is,  however,  really 
the  equivalent  of  PbsOi  in  terms  of  PbO. 

Litharge. — Treat  1  gram  with  20  cc.  of  cone.  HC1.  Cover 
and  heat  on  the  steam  bath  for  fifteen  minutes.  Add  100  cc.  of 
hot  water  and  boil.  (If  there  are  any  insoluble  impurities,  filter 
them  out,  wash  with  boiling  water,  dry  and  weigh.)  Add  NELiOH 
until  a  white  permanent  precipitate  forms.  Redissolve  with  a 
slight  excess  of  acetic  acid,  heat  to  boiling  and  precipitate  with 
K2Cr2O7  as  under  Total  Lead  in  White  Lead,  page  212.  Weigh 
as  PbCr04.  Calculate  to  PbO  and  subtract  from  the  latter  the 
equivalent  of  the  PbsO4  in  terms  of  PbO.  The  difference  will  be 
the  PbO  actually  present  as  such  in  the  material. 


ANALYSIS  OF  PAINTS  AND   PAINT  MATERIALS       211 

CALCULATIONS.— PbCrO4  X  0.6906  =  PbO. 
Pb3O4X  0.9767  =  PbO. 

NOTE. — In  impure  materials  the  impurities  or  adulterations  likely  to  be 
found  are  organic  dyes  and  water  soluble  materials.  The  sample  should 
also  be  tested  for  nitrate,  nitrite,  carbonate,  and  sulfate.  Organic  coloring 
matter  may  generally  be  detected  by  adding  20  cc.  of  95%  alcohol  to  2  grams  of 
the  pigment;  then  heat  to  a  boil  and  let  settle.  Pour  off  the  alcohol,  boil 
with  water  and  let  settle.  Then  use  very  dilute  NH4OH.  If  either  the  alcohol, 
NH4OH  or  water  is  colored,  it  indicates  organic  coloring  matter.  The  quan- 
titative determination  of  such  adulteration  is  difficult  and  must  be  generally 
estimated  by  difference. 

REFERENCE. — U.  S.  Dept.  of  Agriculture,  Bur.  of  Chem.,  Bulletin  109, 
revised  (1912). 

WHITE  LEAD 
(BASIC  CARBONATE) 

General. — The  theoretical  composition  of  white  lead  is 
Pb(OH)2-2PbC03.  The  analysis  of  this  would  show:  . 

Total  lead,  calculated  as  PbO 86.33% 

Carbon  dioxide,  C02 11 .35% 

Equivalent  to: 

Lead  hydroxide,  Pb(OH)2 31 . 10% 

Lead  carbonate,  PbC03 68.90% 

It  is  furnished  to  the  trade  either  dry  or  ground  in  oil.  In  the 
latter  case,  the  amount  of  oil  is  generally  about  8%. 

The  pigment  of  commercial  white  leads  generally  shows  between 
11  and  13%  of  C02.  There  should  be  no  appreciable  acid-insoluble 
material  and  no  acetates  present.  The  pigment  should  contain 
at  least  98%  of  white  lead,  calculated  to  the  above  formula. 

Vehicle  (Oil). — Pour  about  50^75  grams  of  the  thoroughly 
mixed  material  into  a  small  beaker  and  weigh  it  in  the  beaker 
together  with  a  stirring  rod.  Dry  and  weigh  one  of  the  specially 
hardened  extraction  thimbles  with  a  plug  of  cotton  wool  in  the  end 
of  it.  Remove  the  cotton  and  fill  the  thimble  about  two-thirds  full 
of  the  pigment,  pouring  it  from  the  beaker  by  means  of  the  stirring 
rod.  Weigh  the  beaker  again,  and  from  the  difference  in  weight 
obtain  the  amount  of  material  taken.  Plug  the  thimble  with  the 


212 


TECHNICAL  METHODS  OF  ANALYSIS 


cotton  and  place  in  a  Soxhlet  extractor.  Fill  the  extractor  about 
two-thirds  full  of  ether,  and  let  stand  at  least  an  hour  before  start- 
ing the  siphoning.  Then  extract  until  no  more  oil  is  removed. 
Dry  the  thimble  with  the  extracted  pigment  and  weigh  it. 

NOTE. — When  it  is  not  necessary  to  determine  the  relative  proportions  of 
oil  and  pigment,  the  oil  can  be  extracted  more  quickly  by  stirring  some  of  the 
material  up  with  86°  naphtha,  centrifuging  and  decanting  the  liquid  several 
times  until  no  more  oil  is  left  in  the  pigment. 

ANALYSIS  OF  PIGMENT 

Insoluble  Matter. — Dissolve  0.5  gram  of  the  dry  pigment 
(well  mixed  and  ground)  in  hot  dil.  HNOs.  If  an  appreciable 
amount  of  insoluble  material  remains,  filter  the  solution,  wash 
the  residue  with  hot  water,  ignite  and  weigh. 

Total  Lead. — Dilute  the  filtrate  from  the  insoluble  material 
to  about  250  cc.  and  add  NILiOH  until  the  solution  is  slightly 
alkaline.  Then  add  dil.  acetic  acid  in  slight  excess.  Heat  to 
boiling,  and  add  a  hot  solution  of  K^C^O?  in  excess.  Sufficient 

bichromate  solution  should  be 
added  so  that  when  the  PbCrO4 
settles,  the  supernatant  liquor  is 
distinctly  yellow  or  orange.  Boil 
until  the  precipitate  settles 
quickly  (about  two  minutes 
generally  suffices).  Filter 
through  a  weighed  Gooch 
crucible.  Wash  with  hot 
water,  dry  at  110°  C.,  set  the 
Gooch  crucible  in  a  larger 
platinum  crucible,  ignite  gently, 
cool  in  a  desiccator  and  weigh 
as  PbCr04. 

Carbon  Dioxide. — For  this 
determination  use  Mohr's  alka- 
limeter  (Fig.  13).  Weigh  out 

FIG.  13.-Alkalirneter  for  Carbon      5-10  SramS  °f  the  dried  pigment 
Dioxide  Determination.  and  b™sh  it  carefully  by  means 

of  a  funnel  scoop  into  the  lower 
chamber  of  the  alkalimeter  (A).    Add  a  few  cc.  of  water  and 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       213 

connect  the  acid  chamber  (B).  Close  the  stop-cock  (E)  and  fill 
this  chamber  nearly  full  of  dil.  HC1  or  HNO3  (1:4).  In  the 
chamber  (C)  should  be  just  enough  cone.  H2S04  to  make  a  seal. 
Weigh  the  whole  apparatus.  Open  the  stop-cock  (E)  and  let 
the  dilute  acid  run  slowly  upon  the  pigment.  When  nearly  all 
the  acid  has  run  in,  close  the  stop-cock.  Complete  the  reaction 
by  placing  the  whole  apparatus  in  a  beaker  and  setting  on  the 
steam  bath.  Make  sure  that  all  the  pigment  has  been  dissolved, 
then  allow  the  alkalimeter  to  come  to  room  temperature.  Attach 
a  small  rubber  tube  to  the  outlet  of  the  side  arm  at  (D)  and  open 
the  stop-cock.  Suck  air  slowly  and  carefully  through  the  appa- 
ratus until  all  the  liberated  CCb  has  been  replaced  by  air;  then 
weigh  on  the  balance.  The  loss  in  weight  is  CC>2. 

Lead  Acetate. — Dry  some  of  the  extracted  pigment  at  105°  C. 
Place  a  little  on  a  watch  glass  and  moisten  with  a  few  drops  of 
KI  solution.  If  acetates  are  present  a  yellow  color  will  form. 
To  determine  the  amount,  weigh  5-10  grams  of  the  pigment 
into  a  distilling  flask,  add  200  cc.  of  water  and  5  cc.  of  sirupy 
H3PO4  and  distill*  until  the  distillate  no  longer  comes  over  acid. 
Then  titrate  the  distillate  with  0.1  N  NaOH  and  phenolphthalein. 

1  cc.  0.1  N  NaOH  =  0.01897  gram  Pb(C2H3O2)2-3H2O. 

CALCULATIONS. — Calculate  the  PbCrO4  to  PbO.  Calculate 
the  CO2  to  PbCO3.  From  the  total  PbCrO4  subtract  the  equiva- 
lent of  PbCO3  and  of  Pb(C2H302)2  and  calculate  the  difference  to 
Pb(OH)2. 

PbCr04X0.6906  =  PbO. 

CO2X  6.0724      =PbCO3. 

PbCO3  X  1.2095  =  PbCrO4. 

Pb(C2H3O2)2  •  3H2O  X0.8521  =  PbCr04. 

PbCr04  X  0.7464  =-•  Pb(OH)2. 

CHROME  YELLOW 

General. — The  most  important  yellow  pigment  is  chrome 
yellow,  which  varies  from  a  light  yellow  color  to  deep  orange. 
The  lighter  shades  generally  contain  PbS04  as  well  as  PbCr04, 
while  the  deep  orange  contains  some  basic  lead  chromate.  Pure 
chrome  yellow  should  contain  only  PbCrO4,  PbSO4  (or  white  lead) 


214  TECHNICAL  METHODS  OF  ANALYSIS 

and  possibly  some  basic  lead  in  the  darker  shades.  A  chrome 
yellow  should  be  considered  adulterated  if  it  contains  anything 
in  appreciable  amount  besides  insoluble  lead  compounds.  The 
following  analytical  method  applies  to  the  dry  pigment  or  to  the 
pigment  of  a  paste  after  the  vehicle  has  been  removed. 

Moisture. — Dry  2  grams  in  a  watch  glass  or  dish  to  constant 
weight  at  105°  C. 

NOTE. — As  the  pigment  of  pastes  is  generally  dried  in  extracting  the  oil, 
the  determination  of  moisture  in  such  cases  is  superfluous. 

Insoluble  Impurities. — Treat  1  gram  in  a  beaker  with  20  cc. 
of  cone.  HC1,  cover  and  heat  on  a  steam  bath  for  fifteen  minutes. 
Add  100  cc.  of  hot  water,  boil  (the  solution  should  be  complete), 
filter,  wash  very  thoroughly  with  hot  water  and  ignite  in  a  plati- 
num crucible,  cool  in  a  desiccator  and  weigh  the  insoluble 
impurities. 

If  the  impurities  are  considerable  in  amount,  evaporate  the  resi- 
due twice  with  HF  and  a  few  drops  of  dil.  H^SCU,  drive  off  the 
H2S04,  ignite  and  weigh.  If  the  insoluble  impurities  are  mostly 
volatile  with  HF,  report  as  silica.  If  the  residue  from  the  HF 
treatment  is  considerable,  fuse  it  with  KHSO4  and  dissolve  in  water 
containing  a  little  HC1.  Filter  out,  ignite  and  weigh  any  insoluble 
residue.  If  the  treatment  with  HF  was  complete,  this  residue  is 
probably  BaSO4,  but  it  should  be  confirmed  qualitatively. 

The  filtrate  from  the  BaS04  will  contain  insoluble  Fe2Os, 
A^Og,  CaO,  and  MgO.  Iron  and  alumina  alone  indicate  clay  or 
similar  mineral  matter;  a  considerable  airount  of  MgO  generally 
indicates  talc.  It  is  not  generally  necessary  to  determine  the 
insoluble  Fe,  Al  and  Mg;  the  difference  between  the  BaSC>4 
(if  any)  and  the  total  insoluble  may  be  reported  as  "  silicious  mat- 
ter." 

Total  Lead. — Nearly  neutralize  the  filtrate  from  the  insoluble 
with  NHjOH,  and  dilute  to  350  cc.  Pass  in  a  rapid  current  of 
H2$  for  ten  minutes.  Cover  with  a  watch  glass,  place  on  the  steam 
bath  and  let  settle.  Test  a  portion  of  the  clear  liquid  for  complete 
precipitation  by  diluting  with  an  equal  volume  of  water  and  passing 
in  more  H2$.  If  precipitation  is  not  complete,  dilute  the  whole 
to  about  500  cc.  and  pass  in  more  H2$.  Finally  filter  out  the  PbS 
and  wash  rapidly  with  water  containing  a  little  H2S.  Dissolve  the 
PbS  with  hot  cone.  HNOs  containing  a  little  bromine  water,  dilute 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       215 

to  about  100  cc.,  filter  out  sulfur  if  necessary,  cool,  add  5  cc.  of 
cone.  H2SO4  and  evaporate  to  strong  SOs  fumes.  Cool  and  add 
100  cc.  of  water  and  50  cc.  of  alcohol.  Let  stand  one  hour  or 
until  the  PbSO4  settles  clear.  Filter  on  a  weighed  Gooch  crucible, 
wash  with  5%  H2SO4  and  finally  with  alcohol,  dry  at  105°  C., 
set  the  crucible  in  a  larger  platinum  crucible,  ignite  until  pure 
white,  cool  and  weigh  as  PbSO4. 

NOTE. — In  the  presence  of  Cr  the  solution  must  be  very  dilute  and  the  H2S 
passed  in  rapidly  to  get  a  good  separation. 

Iron  Oxide. — Boil  the  filtrate  from  the  PbS  until  free  from  H2S. 
Add  a  few  drops  of  HNOs  and  boil  again.  Add  a  very  slight 
excess  of  NILtOH,  boil,  let  settle,  filter  and  wash  with  hot  water. 
Save  the  filtrate.  Dissolve  the  precipitate  (hydroxides  of  Fe,  Al 
and  Cr)  in  HC1.  Rinse  into  a  500  cc.  flask  and  dilute  to  the  mark. 

To  200  cc.  of  the  above  solution,  add  a  very  slight  excess  of 
NH^OH  and  then  sufficient  Na202  to  oxidize  all  the  Cr.  Boil  until 
all  the  H202  is  expelled.  If  there  is  any  insoluble  residue  filter 
and  wash  slightly.  Dissolve  the  precipitate  in  dilute  HC1,  dilute 
with  water,  add  a  slight  excess  of  NEUOH  and  treat  with  peroxide 
as  before.  Filter,  wash  with  hot  water  and  add  this  filtrate  to  the 
previous  one.  Ignite  the  residue  strongly  in  a  platinum  crucible, 
cool  and  weigh  as  Fe2O3.  Divide  by  0.4  and  multiply  by  100  to 
obtain  the  percentage  of  Fe2Os. 

Lead  Chromate. — Acidify  with  acetic  acid  the  total  filtrate 
from  the  Fe  determination,  boil  until  all  H202  is  decomposed  and 
treat  by  one  of  the  following  methods.  In  either  case  divide  the 
result  by  0.4  and  multiply  by  100  to  obtain  the  percentage  of 
PbCr04. 

(A)  GRAVIMETRIC  METHOD. — Add  a  slight  excess  of  clear  lead 
acetate  solution  (a  basic  solution  can  generally  be  cleared  up  by 
adding  a  few  drops  of  acetic  acid),  digest  on  the  steam  bath  until 
the  precipitate  settles  clear,  and  filter  on  a  weighed  Gooch  crucible, 
washing  with  hot  water;  dry.  set  the  crucible  inside  of  a  larger 
platinum  crucible,  ignite  gently,  cool  in  a  desiccator  and  weigh  as 
PbCrO4.  The  precipitate  should  not  be  allowed  to  stand  in  the 
beaker  an  undue  length  of  time  after  settling  clear  on  account  of 
the  danger  of  becoming  basic,  nor  should  the  solution  be  boiling 
when  the  lead  acetate  is  added  or  at  any  time  after. 


216  TECHNICAL  METHODS  OF  ANALYSIS 

(B)  VOLUMETRIC  METHOD. — Cool  the  solution  which  has  been 
freed  from  H202,  make  distinctly  acid  with  H2SO4,  add  a  meas- 
ured excess  of  0. 1  N  ferrous  ammonium  sulf ate  solution  and  titrate 
the  excess  of  the  latter  with  0.1  N  K^toO?,  using  potassium 
ferricyanide  as  outside  indicator.  The  end  point  is  the  disap- 
pearance of  the  blue  color  first  produced.  From  the  amount  of 
ferrous  ammonium  sulfate  oxidized,  calculate  the  amount  of 
PbCrO4  corresponding  to  the  chromium. 

CALCULATION.— 1  cc.  of  0.1  N  Fe(NH4)2(SO4)2  =  0.01077 
gram  PbCrO4 

Alumina. — Alumina  is  very  seldom  present  but  may  be  deter- 
mined in  an  aliquot  of  the  solution  prepared  above  under  Iron 
Oxide  by  oxidizing  with  Na2C>2,  filtering,  rendering  the  filtrate 
slightly  acid  with  HC1  and  then  very  slightly  alkaline  with 
NHiOH.  This  precipitates  A1(OH)3.  Filter  out,  wash  with  hot 
water,  ignite  in  the  blast,  cool  and  weigh  as  A^Os.  (After  adding 
the  NHUOH,  the  solution  should  not  be  boiled,  as  some  Cr(OH)s 
may  also  thus  be  thrown  down.) 

Zinc  Oxide. — Into  the  filtrate  from  the  original  precipitate  of 
hydroxides  of  Fe,  Al  and  Cr  (which  should  be  ammoniacal)  pass 
H2S,  heat  to  boiling,  and  filter  through  a  hardened  filter,  washing 
with  H2S  water.  Dissolve  the  ZnS  in  a  slight  excess  of  HC1,  dilute 
to  200  cc.,  boil  off  the  H2S,  add  a  slight  excess  of  NH4OH  and  then 
an  excess  of  acetic  acid.  Heat  to  boiling  and  add  an  excess  of 
ammonium  phosphate  solution.  Stir  thoroughly  and  let  stand 
until  clear;  filter  and  wash  with  water  on  a  porcelain  Gooch 
crucible,  dry,  ignite  and  weigh  as  Zn2P2O7.  Calculate  to  ZnO. 

CALCULATION.— Zn2P2O7  X  0.5339  =  ZnO. 

Lime. — (Lime  is  seldom  present  unless  the  material  is  adul- 
terated with  gypsum.)  To  the  ammoniacal  filtrate  from  the  ZnS 
add  an  excess  of  hot  sodium  or  ammonium  oxalate  solution  and 
determine  the  CaO  in  the  usual  way. 

Magnesia. — The  MgO  is  determined  in  the  filtrate  from  the 
CaO  in  the  usual  way  by  precipitating  as  MgNHjPO4.  It  is 
almost  never  present  in  a  chrome  yellow  in  an  acid-soluble  form. 

Total  SO3. — Dissolve  1  gram  of  the  pigment  by  heating  with 
20-25  cc.  of  HC1  as  described  under  Insoluble  Impurities.  Filter 
and  wash  with  hot  water  and  dilute  to  about  400  cc.  Heat  to 
boiling  and  add  an  excess  of  hot  BaCb  solution,  drop  by  drop; 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       217 

boil  for  0.5  hour  and  let  stand  on  the  steam  bath  until  the  pre- 
cipitate settles  clear.    Filter  and  wash  with  hot  water,  ignite  in  a 
platinum  crucible  and  weigh  as  BaSO4.     Calculate  to  SOs. 
CALCULATION.— BaSO4  X  0.3430  =  S03. 

NOTE. — The  solution  must  be  kept  hot  and  dilute  to  prevent  contamina- 
tion of  the  precipitate  with  lead. 

Calculation  of  Results. — The  PbCr(>4  is  obtained  directly. 
Calculate  the  SOs  to  PbSO4  and  subtract  this  from  the  total  Pb 
calculated  as  PbSO4.  From  the  remainder  subtract  the  equiva- 
lent of  the  PbCrC>4.  Calculate  the  remaining  lead  to  PbO  and 
report  as  basic  PbO;  or,  if  carbonates  are  present,  calculate  to 
white  lead,  2PbCO3-Pb(OH)2.  The  small  amounts  of  Fe2O3, 
CaO,  etc.,  are  reported  as  such,  unless  it  is  evident  that  calcium 
carbonate  or  sulfate  is  present. 

NOTE. — Some  chrome  yellows  contain  barium  phosphate,  barium  sulfate 
or  calcium  sulfate  in  place  of  the  PbSO4;  sometimes  also  lead  citrate  is  used. 

FACTORS.— BaSO4   Xl.2991  =  PbSO4. 
PbCrO4  X  0.9383  =  PbSO4. 
PbS04   X 0.7360  =  PbO. 
PbSO4   X  0.8526  =  White  Lead. 
SO3        X2.1504  =  CaSO4-2H2O. 

REFERENCE. — Bulletin  109  (Revised)  U.  S.  Bur.  of  Chem.,  page  29. 


OIL  VARNISHES 

General. — The  methods  of  analysis  for  varnishes  are  far  from 
satisfactory.  Several  methods  for  the  determination  of  gums  have 
been  proposed,  but  none  of  them  is  reliable.  It  is,  therefore, 
advisable  to  omit  this  determination  and  report  the  combined 
percentage  of  oil  and  gums.  In  case  it  is  desired  to  get  an  approx- 
imate estimate  of  the  gums,  Boughton;s  method  as  described 
in  Technologic  Paper  No.  65  of  the  Bureau  of  Standards,  may  be 
used. 

Care  should  be  used  in  passing  final  judgment  on  a  varnish 
merely  from  chemical  tests,  as  the  gloss,  working  qualities  and 
durability  depend  largely  upon  the  quality  of  the  gum  used,  the 
quality  and  treatment  of  the  oil,  the  quality  of  the  driers  and 


218  TECHNICAL  METHODS  OF  ANALYSIS 

especially  as  to  how  the  varnish  was  prepared  as  regards  heat, 
method  of  cooking,  aging,  filtering,  etc. 

In  the  manufacture  of  oil  varnish  the  resins  or  "  gums " 
are  melted  and  at  the  proper  time  the  oil  and  driers  are  added. 
The  mass  is  mixed  and  heated,  then  cooled  and  thinned,  filtered 
and  run  into  settling  tanks  where  it  is  aged.  The  time  of  heat- 
ing, temperature,  etc.,  depend  upon  the  nature  of  the  varnish  and 
vary  greatly  for  different  kinds. 

Many  different  resins  are  used,  such  as  Kauri,  Zanzibar,  Pon- 
tianak,  Manila  and  Colophony  (rosin).  Generally  the  harder 
resins  are  more  valuable.  The  principal  oils  used  are  Linseed 
and  China  Wood  (Tung  Oil).  Common  thinners  are  turpentine 
and  light  mineral  oils.  Compounds  of  Pb  and  Mn  (and  some- 
times Co)  are  used  as  driers,  and  if  rosin  is  present,  lime  is  gen- 
erally added  to  harden  it. 

The  following  tests  are  of  value  in  judging  the  quality  of  a 
varnish: 

Appearance  and  Odor. — Transfer  the  sample,  if  it  is  in  a  metal 
container,  to  a  glass-stoppered  cylinder  or  bottle  and  note  its 
appearance,  color,  transparency,  body,  and  whether  any  sediment 
is  present.  The  presence  of  light  petroleum  oil  or  wood  turpen- 
tine may  often  be  detected  by  the  odor.  After  making  these 
observations,  the  sample  should  be  thoroughly  mixed  before  making 
the  remaining  tests. 

Specific  Gravity. — Determine  with  a  pycnometer,  hydrometer 
or  Westphal  balance  at  15.5°  C. 

Flash  Point. — Determine  the  flash  point  as  described  in  the 
method  for  Lubricating  Oils  (see  page  255),  using  a  low  flame; 
begin  testing  at  65°  F.  and  stir  the  varnish  while  heating.  A 
low  flash  point  may  indicate  light  petroleum  oil.  Turpentine 
flashes  at  about  93°  F. 

Viscosity. — The  determination  of  viscosity  is  not  generally 
necessary  but  may  throw  some  light  on  its  working  qualities,  par- 
ticularly in  comparison  with  other  varnishes.  Sufficiently  accurate 
comparative  results  may  be  obtained  by  using  a  100  cc.  Dudley 
pipette  and  comparing  with  water  as  described  in  the  method  for 
Glue  (page  323).  The  viscosity  should  be  run  at  20°  C. 

Volatile  Thinners. — Weigh  100  grams  of  the  varnish  into  a 
500  cc.  flask,  connect  with  a  spray  trap  and  a  water  condenser,  and 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS.     219 

pass  through  it  a  current  of  steam,  first  heating  the  flask  in  an  oil 
bath  at  100°  C.  With  the  steam  still  passing  through,  raise  the 
temperature  of  the  bath  to  130°  C.  Catch  the  distillate  in  weighed 
glass-stoppered  graduates,  and  continue  distillation  until  300  cc.  of 
water  have  been  condensed.  Do  not  fill  any  graduate  above  the 
top  mark.  Let  the  distillates  stand  until  they  separate  into  two 
layers,  then  read  the  volume  of  water  and  weigh  each  graduate. 
Subtract  the  volume  of  water  and  weight  of  empty  graduates  and 
the  difference  is  the  weight  of  volatile  thinners.  Filter  the  light 
oils  through  dry  papers  and  examine  for  turpentine  and  petroleum 
oils.  A  slight  error  is  caused  by  the  solubility  of  turpentine  in 
water;  this  amounts  to  about  0.3-0.4  cc.  for  each  100  cc.  of 
water. 

When  sufficient  varnish  is  available,  it  is  well  to  take  another 
portion  and  distill  without  steam  or  spray  trap,  placing  the 
weighed  flask  in  an  oil  bath.  Note  the  temperature  of  the  bath 
at  which  distillation  begins,  and  continue  distillation  at  a  tem- 
perature of  185°  C.  in  the  oil  bath,  finally  raising  the  temperature 
to  200°  C.  This  method  generally  tends  to  give  lower  results  on 
volatile  oils  than  the  steam  distillation  method ;  but  the  distillate 
can  be  tested  for  water-soluble  volatile  liquids,  which  would  be 
lost  by  the  steam  distillation. 

Fixed  Oils  and  Gums. — The  percentage  of  fixed  oils  and  gums 
is  obtained  by  subtracting  the  percentage  of  volatile  thinners 
from  100.  A  check  upon  this  determination  is  obtained  by 
weighing  the  residue  from  the  dry  distillation.  In  case  an  actual 
determination  of  the  approximate  amount  of  gums  is  required, 
use  Boughton's  method  previously  referred  to. 

Acid  Number. — Determine  the  acid  number  as  described  on 
page  242  using  10  grams  of  the  varnish. 

Rosin. — After  determining  the  acid  number,  decant  the  alcohol, 
evaporate  and  apply  the  Liebermann-Storch  test;  or  test  the  orig- 
inal varnish  as  follows: 

Pour  about  5  cc.  into  9,  separatory  funnel,  add  an  equal  volume 
of  C$2,  shake  and  add  10  cc.  of  acetic  anhydride.  Let  stand  until 
completely  separated.  Draw  off  the  lower  layer  of  anhydride. 
Pour  1-2  cc.  of  this  into  an  inverted  crucible  cover,  add  carefully 
by  means  of  a  stirring  rod  1  drop  of  H2SO4  (1  :  1)  to  the  edge  of  the 
cover  so  that  it  will  mix  slowly  with  the  anhydride.  If  rosin  is 


220     .  TECHNICAL  METHODS  OF  ANALYSIS 

present  a  characteristic  fugitive  violet  color  will  result.  Do  not 
confuse  this  with  the  brown  or  reddish  brown  color  often  given  by 
other  gums. 

Ash. — Determine  the  ash  in  10  grams,  using  a  quartz  or  por- 
celain dish  and  carrying  out  the  incineration  at  a  low  heat, 
best  in  a  muffle.  Determine  the  reaction  of  the  ash  to  litmus 
paper  and  make  a  qualitative  analysis.  It  is  frequently  well  to 
make  a  quantitative  determination  of  CaO,  a  large  amount  of 
which  indicates  rosin.  It  is  sometimes  advisable  to  determine 
the  percentages  of  Pb  and  Mn.  Some  Pb  will,  however,  be  lost 
in  the  ashing,  and  if  a  correct  determination  is  required,  proceed 
as  under  the  determination  of  Drying  Salts  in  Japan  Driers 
(see  below). 

Examination  of  Films. — Flow  the  varnish  on  a  carefully  cleaned 
plate  of  glass  and  let  dry  at  room  temperature  in  a  vertical  position. 
Note  the  time  required  for  the  varnish  to  "  set  to  touch,"  i.e.,  to 
lose  its  tackiness,  and  also  the  time  required  for  drying  hard.  After 
twenty-four  hours  examine  the  film,  noting  transparency,  hardness, 
elasticity  and  tendency  to  dust  by  scratching.  After  thoroughly 
drying,  immerse  the  plate  in  water  overnight,  dry  without  heat 
and  note  the  appearance. 

Practical  Tests. — The  working  quality  of  a  varnish  must  be 
determined  by  application  on  wood  and  it  is  best  to  make  this 
test  on  well-seasoned  and  perfectly  smooth  white  pine.  Apply  a 
thin  coating  of  the  varnish,  let  dry  and  sandpaper  down  smooth 
and  then  apply  the  coat  to  be  tested.  Observe  how  the  varnish 
works  under  the  brush,  character  of  coat,  etc.  This  panel,  after 
drying,  may  be  used  for  further  testing  as  to  whether  the  varnish 
will  stand  rubbing,  etc. 

NOTES. — (1)  "  Short  oil  "  varnishes  contain  considerably  more  resin  than 
oil,  and  "  long  oil  "  varnishes  vice  versa. 

To  test,  place  10  cc.  of  varnish  in  a  small  beaker  and  add  50  cc.  of  benzine 
which  has  been  previously  cooled  to  5°  C.  If  the  varnish  is  "  short  oil," 
the  gums  will  be  partly  precipitated  and  light  in  color;  if  a  "  long  oil  "  varnish, 
there  will  be  very  little  precipitation  and  the  solution  will  be  dark  colored. 
Interior  varnishes  should  be  "  long  oil  "  for  the  best  quality  of  work  and 
exterior  varnishes  should  always  be  "  long  oil."  Rubbing  varnishes  should 
be  "  short  oil." 

(2)  The  Navy  specification  for  Interior  Varnish  for  Naval  Vessels,  1906, 
requires: 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       221 

(a)  Flash  above  105°  F. 

(6)  Set  to  touch  in  6-8  hours. 

(c)  Dry  hard  within  twenty-four  hours  at  70°  F. 

(d)  Must  stand  rubbing  with  pumice  stone  and  water  within  twenty-four 
hours  after  application  without  sweating  and  must  polish  in  seventy-two  hours 
with  rotten  stone  and  water. 


JAPAN  DRIERS 

General. — The  analysis  of  Japan  driers  is  in  general  conducted 
in  the  same  way  as  that  of  Oil  Varnish,  with  the  following  modi- 
fications: 

Volatile  Thinner. — Weigh  quickly  5  grams  from  a  weighing 
bottle  into  a  glass  Petri  dish  and  dry  for  three  hours  at  100°  C. 
Cool  and  weigh.  The  loss  represents  the  amount  of  volatile  thin- 
ner, which  is  generally  about  65%. 

Drying  Salts. — The  most  generally  used  driers  are  linoleates, 
resinates  or  borates  of  Pb  and  Mn,  or  mixtures  of  these  substances. 
As  a  rule,  in  light  Japans  manganese  borate  is  used ;  in  dark  Japans, 
manganese  oxide;  and  medium  Japans,  lead  oxide.  The  most 
common  composition  is  a  mixture  of  Mn  borate  and  PbO.  Zinc 
is  now  seldom  used.  Qualitative  tests  for  Mn,  Pb  and  Zn  are 
generally  sufficient,  but  if  a  quantitative  determination  is  desired 
proceed  as  follows: 

Place  25  grams  in  a  250  cc.  Erlenmeyer  flask  and  add  25  cc.  of  a 
mixture  of  equal  parts  of  gasoline  and  turpentine.  Add  50  cc. 
of  HNOs  (1:1)  and  let  stand  one  hour,  shaking  every  ten  min- 
utes. Then  immerse  in  hot  wate  and  shake  gently.  Keep 
away  from  any  flame.  When  thoroughly  hot,  mix  with  a  circular 
motion  to  get  rid  of  most  of  the  gasoline.  When  cool,  pour  into  a 
separatory  funnel,  draw  off  the  lower  aqueous  layer  into  a  casserole 
and  wash  the  upper  oily  layer  4-5  times  with  warm  water.  Add 
the  washings  to  the  casserole  and  evaporate  to  dryness  under  the 
hood.  Dissolve  by  warming  with  dil.  HNOs.  Filter  into  a  250  cc. 
flask  and  make  up  to  the  mark. 

LEAD. — To  100  cc.  of  the  above  solution  add  5  cc.  of  cone. 
H2S04  and  evaporate  on  the  hot  plate  to  strong  fumes.  Cool, 
add  100  cc.  of  water  and  heat  to  boiling  to  dissolve  anhydrous 
FeSCU  if  present.  Let  stand  until  cooled  and  the  precipitate  has 
settled  clear.  Filter  on  a  Gooch  crucible  and  wash  with  5% 


222  TECHNICAL  METHODS  OF  ANALYSIS 

H2S04.  Transfer  the  filtrate,  which  should  be  about  150  cc.,  to 
a  beaker  and  wash  the  PbSO4  on  the  Gooch  crucible  with  50% 
alcohol.  Do  not  collect  the  alcoholic  filtrate  in  the  main  body  of 
the  filtrate  as  it  is  used  merely  to  wash  out  the  acid  from  the 
PbSC>4.  Dry  the  Gooch  crucible  and  contents  and  place  in  a 
larger  platinum  crucible.  Ignite  gently,  cool  in  a  desiccator  and 
weigh  as  PbS04.  Calculate  to  PbO. 

CALCULATION.— PbS04  X  0.7360  =  PbO. 

ZINC. — If  present,  Zn  may  be  determined  in  the  filtrate  from 
the  PbS04.  To  the  filtrate  in  the  beaker  add  50  cc.  of  30%  NaOH 
solution  and  electrolyze  as  described  under  Zinc  on  page  146, 
finally  weighing  as  metallic  Zn. 

MANGANESE. — The  manganese  will  be  present  as  hydroxide 
in  the  solution  after  electrolysis  of  the  Zn.  Dilute  this  solution 
to  about  300-400  cc.,  filter,  and  wash  with  hot  water.  Wash 
into  a  200  cc.  Erlenmeyer  flask  with  50  cc.  of  warm  HNOs  (1  :  3), 
cool,  add  about  0.5  gram  of  sodium  bismuthate  and  proceed  as 
described  under  Manganese  on  page  110. 

NOTES. — (1)  The  following  specifications  of  the  P.  &  R.  Railroad,  1906,  will 
give  an  idea  of  the  requirements  of  a  good  Japan. 

The  material  desired  consists  of  a  pure  turpentine  hardener  and  oil  drier, 
conforming  to  the  following: 

(a)  When  equal  parts  by  weight  of  the  Japan  and  of  pure  turpentine  are 
thoroughly  mixed  and  poured  over  a  slab  of  glass,  which  is  then  placed  nearly 
vertical  at  a  temperature  of  100°  F.,  with  a  free  access  of  air  but  not  exposed 
to  draft,  the  coating  shall  be  hard  and  dry,  neither  brittle  nor  sticky,  in  not 
exceeding  twelve  minutes. 

(6)  When  thoroughly  mixed  with  pure  raw  linseed  oil  at  the  ordinary 
temperature  in  proportions  of  5%  by  weight  of  Japan  to  95%  by  weight  of  raw 
linseed  oil,  no  curdling  shall  result,  nor  any  marked  separation  or  settling  on 
standing. 

(c)  When  the  above  mixture  is  flowed  over  a  slab  of  glass,  which  is  then 
placed  nearly  vertical  at  a  temperature  of  100°  F.,  with  free  access  to  air  but 
not  exposed  to  draft,  the  coating  shall  dry  throughout,  neither  brittle  nor 
sticky,  in  not  exceeding  two  hours. 

(d)  When  5  cc.  of  the  Japan  are  poured  into  95  cc.  of  pure  turpentine  at 
the  ordinary  temperature,  and  thoroughly  shaken,  a  clear  solution  shall  result, 
without  residue,  on  standing  one  hour. 

(e)  After  evaporation  of  the  turpentine,  the  solid  residue  must  be  h&rd 
and  tough,  and  must  not  "  dust  "  when  scratched  with  a  knife. 

(/)  Benzine  or  mineral  oil  of  any  kind  will  not  be  permitted. 
(2)  The  U.  S.  Navy  Specification  is  as  follows: 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       223 

Japan  drier  must  not  flash  below  105°  F.  (open  tester),  must  be  of  the  best 
quality  and  made  from  pure  kauri  gum,  pure  linseed  oil,  pure  spirits  of  tur- 
pentine, and  lead  manganese  driers,  and  be  free  from  adulterants  and  all 
other  foreign  materials,  must  set  to  touch  in  from  one-quarter  to  one  hour, 
dry  elastic  in  from  eighteen  to  twenty-one  hours  at  a  temperature  of  70°  F., 
and  must  not  rub  up  or  powder  under  friction  by  the  finger.  When  mixed 
with  pure  raw  linseed  oil  in  the  proportion  of  8  parts  of  oil  to  1  part  of  drier, 
must  remain  clear  for  two  hours  and  set  to  touch  in  from  six  to  seven  hours  at 
a  temperature  of  70°  F. 

REFERENCES. — Bureau  of  Standards:  Technologic  Paper  No.  65;  Bureau 
of  Chemistry:  Bulletin  109,  revised;  Holley  and  Ladd:  "  Mixed  Paints,  Color 
Pigments  and  Varnishes." 

SHELLAC  AND  SHELLAC  VARNISHES 

General. — Dry  shellac  occurs  on  the  market  in  two  forms, 
orange  shellac  and  bleached  shellac.  There  are  many  different 
grades  of  orange  shellac.  Bleached  shellac,  however,  is  generally 
of  a  high  grade  of  purity.  In  making  shellac  varnishes,  the  dry 
lac  is  dissolved  in  alcohol,  generally  in  the  proportions  of  about 
5  Ibs.  of  the  shellac  to  a  gallon  of  alcohol.  Formerly  methyl 
alcohol  was  almost  universally  used  but  now  denatured  alcohol  is 
largely  employed. 

SAMPLING  OF  DRY  SHELLAC 

Bleached  shellac  is  sold  in  three  forms, — (1)  as  hanks  or  bars 
containing  approximately  25%  of  water,  (2)  as  ground  bleached 
in  pulverized  form  with  about  the  same  water  content,  (3)  as 
bone-dry  or  kiln-dried  shellac.  The  latter  is  prepared  by  drying 
the  ground  bleached  shellac  in  the  air  or  in  vacuum  driers  at  mod- 
erate temperatures.  It  may  contain  up  to  10%  of  water  or  more. 

In  sampling  bone-dry  bleached  shellac,  a  fairly  large  portion 
(about  1  Ib.)  should  be  taken  from  different  parts  of  the  barrel 
and  finally  ground  by  running  quickly  through  a  coffee  mill.  No 
attempt  should  be  made  to  sieve  it.  It  should  be  rapidly  mixed 
and  transferred  to  a  Mason  jar  with  a  screw  cap  and  a  rubber 
ring  seal.  The  jar  should  not  be  more  than  two-thirds  full,  leaving 
room  for  a  thorough  mixing  by  shaking  the  contents.  It  must  be 
kept  in  a  cool  place  and  tested  as  promptly  as  possible.  If  too 
warm,  the  shellac  may  become  partly  caked,  in  which  case  the 
lumps  must  be  broken  up  by  shaking  the  bottle. 


224  TECHNICAL  METHODS  OF  ANALYSIS 

In  sampling  bars  or  hanks,  it  is  recommended  that  a  whole 
hank  be  taken.  It  should  be  crushed  and  ground  as  rapidly 
as  possible.  Ground  bleached  may  be  treated  as  above,  bearing 
in  mind  that  the  large  amount  of  moisture  present  makes  rapid 
handling  imperative. 

ANALYSIS  OF  DRY  SHELLAC 

Moisture. — Both  the  orange  and  bleached  shellac  give  off  vola- 
tile matter  at  temperatures  approaching  100°  C.  Bleached  shellac 
alters  chemically  at  this  temperature,  losing  its  solubility  in  alco- 
hol. For  these  reasons  the  usual  methods  of  determining  water 
by  heating  in  an  air  bath  at  100-110°  C.  are  not  applicable. 

METHOD  No.  1. — Weigh  5-10  grams  of  the  sample  in  flat- 
bottomed  dishes  about  4  inches  in  diameter  or  in  watch  glasses 
ground  to  fit  and  provided  with  a  clamp.  Then  place  the 
shellac  in  a  desiccator  freshly  filled  with  cone.  H^SCX.  The  con- 
tents of  the  dish  should  be  spread  out  in  a  thin  layer  to  expose  as 
large  a  surface  as  possible.  Exhaust  the  desiccator  by  a  vacuum 
pump  as  completely  as  possible.  With  a  good  vacuum  (3  mm. 
pressure  or  better)  constant  weight  will  be  obtained  in  between 
twenty-four  and  forty-eight  hours.  Absolutely  dry  bleached 
shellac  is  quite  hygroscopic  and  the  final  weight  should  be  taken 
as  rapidly  as  possible. 

METHOD  No.  2. — The  same  results  may  be  obtained  by  drying 
the  shellac  in  a  well-ventilated  air  bath  from  three  to  six  hours  at 
100-110°  F.  (38-43°  C.).  One  or  two  electric  -light  bulbs  pro- 
vide a  convenient  source  of  heat.  The  temperature  should  not  be 
allowed  to  rise  above  43°  C.,  otherwise  sintering  may  occur  and 
retard  drying.  With  poorly  ventilated  ovens  the  drying  may  take 
much  longer.  Completeness  of  drying  should  be  ascertained  by 
continuing  the  treatment  to  constant  weight.  (Check  the 
accuracy  of  results  obtained  in  the  oven  by  comparison  with  a 
test  made  in  a  vacuum  desiccator  before  relying  exclusively  on  the 
oven.) 

Rosin. — Introduce  about  0.200  gram  of  the  shellac  (0.400 
gram  of  bleached  shellac)  finely  ground,  into  a  250  cc.  dry  bottle 
of  clear  glass  with  a  ground-glass  stopper;  add  20  cc.  of  glacial 
acetic  acid  (99%)  and  warm  the  mixture  gently  until  solution  is 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       225 

complete  (except  for  wax).  A  pure  shellac  is  rather  difficult  of 
solution.  Solution  is  quicker  according  to  the  proportion  of  rosin 
present.  Add  10  cc.  of  CHCls  and  cool  the  solution  to  21-24°  C. 
The  temperature  should  be  held  well  within  these  limits  during  the 
test.  Add  20  cc.  of  Wijs  solution  from  a  pipette  or  burette  having 
a  rather  small  delivery  aperture.  Close  the  bottle  and  stand  in  a 
dark  place,  and  note  the  time.  It  is  convenient  to  keep  the  bot- 
tles during  the  test  partly  immersed  in  water,  which  should  be 
kept  as  nearly  as  possible  between  22-23°  C. 

Pure  shellac  will  scarcely  alter  the  color  of  the  Wijs  solution. 
If  in  small  amount,  rosin  will  produce  a  slowly  appearing  red- 
brown  color;  in  large  amount,  rosin  causes  an  immediate  colora- 
tion, increasing  in  intensity  as  time  passes.  At  the  end  of  one  hour 
add  10  cc.  of  10%  KI  solution  and  titrate  immediately  with  0.1  N 
sodium  thiosulfate  solution;  25-30  cc.  may  be  run  in  imme- 
diately, unless  the  shellac  is  very  impure,  and  the  remainder  added 
gradually  with  vigorous  shaking.  Just  before  the  end,  add  a  little 
starch  solution.  The  end  point  is  sharp,  as  the  reaction  products 
of  shellac  remain  dissolved  in  the  chloroform.  Disregard  any  color 
returning  after  a  half  minute  or  so. 

Run  a  blank  determination  with  20  cc.  of  Wijs  solution,  20  cc. 
of  acetic  acid,  10  cc.  of  CHCls  and  10  cc.  of  10%  KI  solution. 
The  blank  is  necessary  on  account  of  the  well  known  effect  of 
temperature  changes  on  the  volume  and  possible  loss  of  strength 
of  the  Wijs  solution. 

Subtract  the  titration  of  the  sample  from  that  of  the  blank 
and  calculate  the  iodine  number  of  the  sample  (percentage  of 
I  absorbed) .  From  this'  calculate  the  percentage  of  rosin. 

CALCULATION. — Let  7  =  percentage  of  rosin; 

A  =  iodine  number  of  mixture ; 
M— 18,*  iodine  number  of  shellac; 
TV  =  228,  iodine  number  of  rosin; 
(A-M) 


then  F=100 


N-M 


NOTES. — (1)  In  the  case  of  grossly  adulterated  samples  or  in  the  testing 

of  pure  rosin,  it  is  necessary  to  use,  instead  of  the  0.2  gram  of  material,  a 

smaller  amount,  say  0.15  gram,  or  even  0.1  gram,  in  order  that  the  excess  of 

iodine  monochloride  may  not  be  too  greatly  reduced,  as  the  excess  of  halogen 

*  For  bleached  shellac  use  10  instead  of  18. 


226 


TECHNICAL  METHODS  OF  ANALYSIS 


is  one  of  the  factors  in  determining  the  amount  of  absorption.  It  is  safe  to 
say  that  in  case  less  than  25  cc.  of  thiosulfate  solution  are  required,  another 
test  should  be  made,  using  a  smaller  amount  of  the  shellac  to  be  tested.  In 
the  case  of  bleached  shellac,  0.4  gram  should  be  taken. 

(2)  The  time  and  temperature  are  very  important  factors.     Variations 
from  the  conditions  prescribed  lead  to  unreliable  results. 

(3)  The  strength  of  the  glacial  acetic  acid  used  in  dissolving  the  shellac, 
and  also  in  the  Wijs  solution,  is  equal  y  important  and  must  be  maintained 
within  the  required  limits. 

The  strength  of  acid  adopted  is  98.8-99.1%,  with  a   melting  point  of 
14.7-15°  C.,  as  determined  by  the  Titer  Method.     (See  page  246.) 

(4)  In  weighing  shellac,  some  difficulty  is  at  times  experienced  on  account 
of  its  electrical  properties;    in  very  dry  weather  it  may  be  found  that  the 
necessary  handling  to  prepare  it  for  weighing  has  electrified  it  and  that  it  may 
be  necessary  to  leave  it  on  the  balance  pan  at  rest  for  a  few  minutes  before 
taking  the  final  weight. 

(5)  The  following  table  shows  how  the  iodine  number  may  be  interpreted  in 
judging  the  quality  of  the  shellac: 


Iodine  Number 

Rosin 
Per  Cent 

Quality 

Orange  Shellac 

Bleached  Shellac 

18  or  less 

10  or  less 

None 

Good 

18-23 

10-15 

0-2.5 

Fair 

23-28 

15-21 

2.5-5 

Poor 

28-34 

21-26 

5-7.5 

Bad 

Over  34 

Over  26 

Over  7.5 

Grossly  adulterated 

(6)  Shellac  having  an  iodine  number  of  23  begins  to  show  rosin  by  the  acetic 
anhydride  test.     (See  page  356.) 

(7)  The  iodine  number  of  bleached  shellac  is  less  than  that  of  crude  shellac. 
Bleached  shellac  of  good  color  will  generally  run  about  8.     Anything  over  10 
would  point  to  adulteration.     The  values  10  and  228  for  shellac  and  rosin 
should  be  used  on  bleached  samples. 

(8)  The  above  method  is  the  one  recommended  by  the  Committee  on  Uni- 
formity in  Technical  Analysis,  American  Chemical  Society. 


ANALYSIS  OF  SHELLAC  VARNISH 

Specific  Gravity. — Determine  the  sp.  gr.  at  15.5°  C.  with  the 
Westphal  balance  or  pycnometer,  as  may  be  most  convenient. 

Total  Solids. — Weigh  from  a  weighing  bottle  about  25  grams 
into  a  flat  evaporating  dish,  evaporate  spontaneously  and  finally 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS        227 

dry   in    an  oven    at  40°   C.    to  constant   weight.     (See   under 
Moisture  in  Dry  Shellac.) 

Rosin. — Determine  the  iodine  number  of  the  dried  residue  and 
calculate  the  percentage  of  rosin  as  described  in  the  analysis  of 
Dry  Shellac  above.  The  residue  must  be  entirely  free  from 
solvent  which  might  affect  the  iodine  number. 

Examination  of  Solvent. — Distill  a  portion  of  the  original  and 
note  the  temperature  at  which  the  solvent  comes  over.  Deter- 
mine the  sp.  gr.  at  15.5°  C.  of  the  latter,  evaporate  a  portion  on 
filter  paper  or  blotter  and  note  the  odor  of  the  last  portions.  In 
the  case  of  denatured  alcohol,  the  first  odor  is  methyl  alcohol  and 
the  final  odor  ethyl  alcohol.  The  boiling  point  will  also  indicate 
whether  the  solvent  is  wood  or  denatured  alcohol. 

Calculate  the  pounds  of  dry  gum  shellac  per  gallon  of  the  sol- 
vent. 

CALCULATION. — Multiply  the  sp.  gr.  of  the  original  by  8.33. 
This  gives  the  weight  per  gallon  of  the  varnish  (A).  This  multi- 
plied by  the  percentage  of  total  solids,  expressed  as  a  decimal,  will 
then  give  the  pounds  of  dry  shellac  per  gallon  of  the  varnish  (B). 
Subtract  (B)  from  (A)  and  the  difference  is  the  weight  of  solvent 
per  gallon  of  varnish  (C).  Divide  (C)  by  the  sp.  gr.  of  the  solvent 
times  8.33;  call  this  (D).  (B)  divided  by  (D)  will  give  the 
pounds  of  dry  shellac  per  gallon  of  solvent. 

REFERENCES. — "  The  Determination  of  Rosin  in  Shellac."  A.  C.  Lang- 
muir,  J.  Soc.  Chem.  Ind.  24,  12  (1905). 

Report  of  the  Sub-committee  on  Shellac-  Analysis.  J.  Amer.  Chem.  Soc. 
29,  1221  (1907). 

"  Analysis  of  Shellac."     Parry,  J.  Soc.  Chem.  Ind.  20,  1245  (1901). 

"  Method  of  Analyzing  Shellac."  Mcllhiney,  J.  Amer.  Chem.  Soc.  30, 867 
(1908). 

Allen's  "  Commercial  Organic  Analysis,"  3d  edition,  Vol.  II,  Part  III, 
page  191. 

"  The  Determination  of  Moisture  in  Shellac."  J.  Ind.  Eng.  Chem.  7, 
633  (1915). 

BLACK  AIR-DRYING  INSULATING  VARNISH  AND  BLACK  BAKING 
INSULATING  VARNISH 

ELECTRIC  RAILWAY  SPECIFICATIONS 

General. — The  materials  which  these  specifications  cover  are 
insulating  varnishes  for  armatures,  field  coils,  etc.,  in  suitable  form 


228  TECHNICAL  METHODS  OF  ANALYSIS 

for  use  as  received.  They  are  a  combination  of  asphalts  and  drying 
oils  as  a  base,  with  a  solvent,  preferably  a  hydrocarbon  solvent 
such  as  benzine  or  naphtha.  It  is  aimed  to  obtain  a  product  which, 
under  the  effects  of  the  continued  heat  of  normal  operating  condi- 
tions, shall  show  the  least  loss  of  plasticity  or  lowering  of  its 
dielectric  strength.  It  must  not  be  sufficiently  fluid  under  these 
conditions  to  be  forced  out  of  the  coils. 

Quality  of  Base. — The  base  must  contain  no  pigment  of  any 
kind.  (It  should  show  no  significant  residue  insoluble  in  benzene 
or  CCU.)  It  must  be  entirely  non-volatile  and  after  application 
as  a  coating,  evaporation  of  solvent  and  drying,  must  become  a 
solid  that  does  not,  at  100°  C.,  become  sufficiently  softened  to  flow. 

Quality  of  Solvent. — The  solvent  must  not  contain  any  alcohol 
or  other  electrically  conductive  material.  It  must  be  entirely 
volatile  without  residue  at  100°  C. 

Amount  of  Solvent. — The  air-drying  varnish  should  not  con- 
tain more  than  60%  by  weight  of  solvent,  and  the  baking  varnish 
not  more  than  50%  when  tested  as  follows: 

Place  400  cc.  of  water  in  a  liter  distilling  flask.  Pour  in  100 
grams  of  the  varnish  and  distill  with  steam.  Continue  the  dis- 
tillation until  no  more  volatile  oil  distills  over,  taking  care  that 
there  is  always  some  water  in  the  distilling  flask  so  that  the  tem- 
perature shall  not  rise  above  212°  F.  Collect  the  distillate  in  a 
graduated  weighed  cylinder  and  weigh  it,  subtracting  the  volume 
of  water  distilled  with  it;  or,  measure  its  volume  and  deter- 
mine its  sp.  gr.  and  calculate  the  weight. 

Drying  Test. — (a)  AIR-DRYING  VARNISH. — Dip  a  piece  of 
clean  window  glass  in  the  varnish  and  dry  in  a  vertical  position  at 
room  temperature  (70°  F.).  It  should  be  set  firmly  in  one  hour 
and  become  free  from  tackiness  in  not  more  than  three  hours. 

(6)  BAKING  VARNISH. — See  under  Dielectric  Strength  below. 

Flexibility. — Place  some  of  the  varnish  in  a  shallow  pan  and 
dip  in  it,  one  at  a  time,  several  sheets  of  glassine  paper  about  1 
foot  square.  Hang  the  sheets  up  and  let  them  dry  perpendicu- 
larly overnight.  (See  below.) 

(a)  AIR-DRYING  VARNISH. — When  thoroughly  dry  the  sheets 
should  be  flexible  and  should  withstand  ordinary  bending  without 
any  of  the  varnish  cracking,  flaking  or  breaking  off. 


ANALYSIS  OF  PAINTS  AND  PAINT  MATERIALS       229 

(b)  BAKING  VARNISH. — Bake  the  sheets  for  ten  hours  at  100°  C. 
They  should  then  withstand  bending  back  flat  on  themselves 
without  any  cracking.  Continue  the  baking  for  ten  days.  They 
should  still  be  flexible  and  withstand  ordinary  bending  without 
cracking. 

Dielectric  Strength. — Use  the  above  sheets  for  testing, 
unbaked  sheets  in  the  case  of  air  drying  varnish  and  sheets  baked 
ten  days  at  100°  C.  in  the  case  of  the  baking  varnish.  Apply  an 
alternating  current  at  low  voltage  and  raise  gradually  until  punc- 
ture occurs.  Make  as  many  tests  as  possible  on  each  sheet  and 
report  the  final  figure  as  the  average  of  at  least  10  breakdowns. 
Also  make  at  least  10  micrometer  measurements  to  obtain  the 
average  thickness  of  the  varnish  film.  The  varnish  should  have  a 
dielectric  strength  of  at  least  1000  volts  for  each  mil  of  thickness. 

Oil  Resisting  Properties. — Take  a  piece  of  ribbon  copper,  4 
inches  long  and  2  inches  wide,  and  dip  for  3.5  inches  of  its 
length  in  the  varnish.  Let  drain  fifteen  minutes.  Place  in  a 
baking  oven  and  bake  until  thoroughly  dry  (20-24  hours  at 
100°  C.).  With  a  pair  of  heavy  scissors  cut  0.5  inch  off  the  bottom 
so  as  to  remove  the  bead  and  all  thickening  of  the  coat.  Also 
trim  0.25  inch  off  each  side  of  the  copper  for  its  full  length.  Take 
a  dish  (metal  or  enamel  ware)  and  fill  it  about  4  inches  deep  with 
water.  On  top  of  this  pour  a  layer  of  about  0.5  inch  of  fairly 
heavy  engine  oil.  Place  the  coated  sheet  of  copper  in  this  mixture 
of  oil  and  water  until  the  oil  comes  to  about  the  middle  of  the 
coat  of  varnish.  Then  boil  the  mixture  vigorously.  At  the  end 
of  every  fifteen  minutes  or  so  remove  the  piece  and  see  whether  the 
varnish  has  suffered  any  injury.  The  coating  should  withstand 
two  hours'  boiling  without  any  effect  and  should  withstand  four 
hours'  boiling  without  any  material  deterioration. 


CHAPTER  VII 

ANALYSIS   OF   OILS,  FATS,   WAXES  AND   SOAPS 
ANIMAL  AND  VEGETABLE  OILS  AND  FATS 

General. — The  usual  determinations  on  materials  of  this  class 
are  specific  gravity,  refractive  index,  iodine  number,  saponification 
number  and  fatty  acid;  and,  in  the  case  of  fats,  melting  point. 
Certain  other  tests  are  often  of  value  in  the  case  of  particular 
oils  or  in  attempting  to  identify  mixtures. 

In  this  method  are  collected  general  procedures  for  such  tests 
as  are  standard.  In  the  case  of  individual  oils,  the  special  method 
for  that  particular  oil  should  be  consulted.  A  table  of  the  so- 
called  "  constants  "  of  various  oils  is  given  on  pages  232-239. 

Preparation  of  Sample. — In  the  case  of  solid  fats,  melt  and  filter, 
using  a  hot  water  funnel.  Make  analyses  on  the  melted  homo- 
geneous mass.  Filter  oils  which  are  not  clear.  Keep  samples 
in  a  cool  place  protected  from  light  and  air  to  avoid  becoming 
rancid.  It  is  best  to  weigh  out  at  once  as  many  portions  as  are 
needed  for  the  various  determinations. 

Specific  Gravity. — (A)  AT  15.5°  C. — Determine  the  sp.  gr. 
at  15.5°  C.  (60°  F.)  with  a  pycnometer  or  Westphal  balance. 
The  pycnometer  should  be  standardized  with  distilled  water  at 
the  same  temperature.  The  Westphal  balance  should  read  1.0000 
in  distilled  water.  If  the  reading  differs  from  this,  divide  the 
reading  in  oil  by  the  reading  in  distilled  water  to  get  the  correct 
sp.  gr.  of  the  oil. 

(B)  AT  TEMPERATURE  OF  BOILING  WATER. — Fill  a  weighed 
sp.  gr.  bottle  (25-50  cc.)  with  freshly  boiled  hot  water.  Place 
in  boiling  water  and  boil  rapidly  for  thirty  minutes.  Replace 
any  evaporation  from  the  bottle  by  addition  of  boiling  water. 
Then  insert  the  stopper,  previously  heated  to  100°  C.,  remove  the 
bottle,  cool  and  weigh. 

230 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS       231 

Dry  the  bottle  at  100°  C.,  fill  with  the  dry,  hot  freshly  filtered 
fat,  entirely  free  from  air  bubbles.  Immerse  in  boiling  water  for 
thirty  minutes.  Insert  the  stopper  previously  heated  to  100°  C., 
cool  and  weigh.  Divide  the  weight  of  fat  by  the  weight  of  water 
previously  found,  to  obtain  the  sp.  gr. 

NOTES. — (1)  Instead  of  standardizing  the  bottle  with  boiling  water,  the 
following  formula  may  be  used  for  calculating  the  weight  of  water  at  100°  C. 
from  the  weight  at  some  other  temperature: 

Wt.  at  100°  C.  =  W-[1  +0.000026  (100-01 
a 

WD 

=  — —  (1.0026-0.0000260; 
a 

where  t  =  temperature  at  which  water  is  weighed; 

D  =  density  of  water  at  100°  C.; 

d  =  density  of  water  at  t°  C.; 
and  W  =  weight  of  water  at  t°  C. 

(2)  The  bottle  with  contents  should  always  be  weighed  at  room  tempera- 
ture. 

Refractive  Index. — Place  the  instrument  so  that  diffused  day- 
light or  any  form  of  artificial  light  can  be  used  for  illumination. 
Circulate  through  the  prisms  a  stream  of  water  at  constant  tem- 
perature. For  fats,  the  standard  temperature  is  40°  C. ;  for  oils  it 
may  be  15,  20  or  25°  C.,  depending  on  circumstances. 

(A)  WITH  ABBE  REFRACTOMETER. — Open  the  double  prism 
by  means  of  the  screw  head  and  place  a  few  drops  of  oil  on  the 
prism.  Let  stand  a  few  minutes  to  come  to  uniform  temperature. 
Move  the  alidade  on  the  side  scale  backward  or  forward  until 
the  field  of  vision  is  divided  into  light  and  dark  portions.  Rotate 
the  screw  head  of  the  compensator  until  a  sharp  colorless  line  is 
obtained  between  the  fields,  then  adjust  this  line  so  that  it  falls 
on  the  point  of  intersection  of  the  2  cross  hairs.  Read  the  refract- 
ive index  directly  on  the  scale. 

NOTES. — (1)  The  correctness  of  the  instrument  should  be  checked  by 
means  of  the  quartz  plate  which  accompanies  it,  using  monobromonaphtha- 
lene.  It  may  also  be  checked  with  distilled  water,  the  index  of  refraction  of 
which  at  20°  C.  is  1.3330.  Apply  to  all  readings  any  correction  found  in 
standardization. 


232 


TECHNICAL  METHODS  OF  ANALYSIS 


ANALYSIS   OF   OILS,    FATS,    WAXES   AND   SOAPS 


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ANALYSIS  OF  OILS,   FATS,' WAXES  AND  SOAPS 


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TECHNICAL  METHODS  OF  ANALYSIS 


(2)  Refractive  index  varies  directly  with  temperature,  increasing  as  tem- 
perature falls  and  vice  versa.  Temperature  correction  may  be  made  as  follows : 

Let  Ri  =  reading  at  h, 

and  Rz  —  reading  at  h ; 

then  #1  =  #2 +0.000365  (fc-fc). 

The  decimal  in  the  formula  represents  the  change  in  refractive  index  for 
each  degree  C. 

(B)  BY  ZEISS  BUTYRO-REFRACTOMETER. — Place  2  or  3  drops 
of  filtered  fat  on  the  surface  of  the  lower  prisms.  Close  the  prisms 
and  adjust  the  mirror  until  it  gives  the  sharpest  reading.  If  the 
reading  is  indistinct  after  running  water  at  constant  temperature 
through  the  instrument  for  some  time,  the  fat  is  unevenly  dis- 
tributed on  the  surfaces  of  the  prisms.  The  instrument  should  be 
carefully  adjusted  by  means  of  a  standard  fluid  supplied  with  it 
and  the  temperature  kept  constant  during  use.  Convert  degrees 
butyro  to  refractive  indices  from  the  following  table: 

BUTYRO-REFRACTOMETER  READINGS  AND  INDICES  OF  REFRACTION 


Reading 

Index 

Reading 

Index 

Reading 

Index 

Reading 

Index 

40.0° 

1.4524 

50.0° 

1.4593 

60.0° 

.4659 

70.0° 

1.4723 

40.5 

1.4527 

50.5 

1.4596 

60.5 

.4662 

70.5 

1.4726 

41.0 

1.4531 

51.0 

1.4600 

61.0 

.4665 

71.0 

1.4729 

41.5 

1.4534 

51.5 

1.4603 

61.5 

.4668 

71.5 

1.4732 

42.0 

1.4538 

52.0 

1.4607 

62.0 

.4672 

72.0 

1.4735 

42.5 

1.4541 

52.5 

1.4610 

62.5 

.4675 

72.5 

1.4738 

43.0 

1.4545 

53.0 

1.4613 

63.0 

.4678 

73.0 

1.4741 

43.5 

1.4548 

53.5 

1.4616 

63.5 

.4681 

73.5 

1.4744 

44.0 

1.4552 

54.0 

.4619 

64.0 

.4685 

74.0 

1.4747 

44.5 

1.4555 

54.5 

.4623 

64.5 

.4688 

74.5 

1.4750 

45.0 

.4558 

55.0 

.4626 

65.0 

.4691 

75.0 

1.4753 

45.5 

.4562 

55.5 

.4629 

65.5 

.4694 

75.5 

1.4756 

46.0 

.4565 

56.0 

.4633 

66.0 

1.4697 

76.0 

1.4759 

46.5 

.4569 

56.5 

.4636 

66.5 

1.4700 

76.5 

1.4762 

47.0 

.4572 

57.0 

.4639 

67.0 

1.4704 

77.0 

1.4765 

47.5 

.4576 

57.5 

.4642 

67.5 

1.4707 

77.5 

1.4768 

48.0 

.4579 

58.0 

.4646 

68.0 

1.4710 

78.0 

1.4771 

48.5 

.4583 

58.5 

.4649 

68.5 

1.4713 

78.5 

1.4774 

49.0 

.4586 

59.0 

.4652 

69.0 

1.4717 

79.0 

1.4777 

49.5 

.4590 

59.5 

.4656 

69.5 

1.4720 

79.5 

1.4780 

ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        241 

Saponification  Number  (Koettstorfer  Number). — Saponify 
about  5  grams  (accurately  weighed)  under  a  reflux  condenser  for 
one  hour  or  longer  with  50  cc.  of  0.5  N  alcoholic  KOH  in  a  250- 
300  cc.  Erlenmeyer  flask.  Run  a  "  blank  "  on  50  cc.  of  the  0.5  N 
alcoholic  KOH  under  the  same  conditions.  Cool  and  titrate  with 
0.5  N  HC1  and  phenolphthalein.  Always  make  duplicate  deter- 
minations. Subtract  the  number  of  cc.  of  acid  used  to  neu- 
tralize the  excess  of  alkali  after  saponification  from  the  number  of 
cc.  required  by  the  "  blank."  Multiply  the  result  by  28.06  and 
divide  by  the  weight  of  sample  to  obtain  the  saponification  number, 
which  represents  milligrams  of  KOH  consumed  by  1  gram  of  oil. 

Alcoholic  KOH  Solution. — Dissolve  29  grams  of  pure  KOH  in 
1  liter  of  95%  alcohol  by  volume.  This  alcohol  should  be  re- 
distilled from  NaOH,  over  which  it  has  been  standing  for  some 
time,  or  boiled  for  a  short  time  under  a  reflux  condenser  with 
stick  NaOH  and  then  distilled.  Mix  thoroughly  and  let  stand 
until  all  carbonate  has  settled  out.  Pour  off  the  clear  solution 
for  use.  , 

Unsaponifiable  Matter. — See  page  261. 

Iodine  Number. — Determine  the  iodine  number  by  the  Wijs 
method.  Weigh  0.2-0.25  gram  of  oil  into  a  wide-mouthed, 
glass-stoppered  bottle.  (For  drying  oils,  such  as  linseed,  use 
between  0.15  and  0.20  gram.)  Add  10  cc.  of  CHCls.  Then  add 
from  a  pipette  25  cc.  of  Wijs  solution;  let  stand  one  hour;  add 
40  cc.  of  10%  KI  solution,  and  titrate  immediately  with  0.1  N 
thiosulfate,  running  in  rapidly  at  first  until  the  color  begins  to 
fade,  then  adding  starch  solution  and  titrating  more  slowly  until 
the  blue  color  disappears.  The  bottle  should  be  stoppered  and 
shaken  during  titration  to  make  sure  that  all  excess  of  iodine  is 
removed  from  the  CHCls.  Two  "blanks"  should  also  be  run 
with  each  determination,  using  10  cc.  of  CHCls,  25  cc.  of  Wijs 
solution,  and  titrating  at  the  end  of  one  hour  exactly  as  above. 
Care  should  be  taken  to  have  the  temperature  the  same  at  the  end 
of  the  determination  as  at  the  beginning. 

Subtract  the  number  of  cc.  of  thiosulfate  required  in  the  oil 
titration  from  the  average  number  of  cc.  required  by  the  2 
"  blanks,"  multiply  by  1.269  and  divide  by  the  weight  of  oil  taken. 
The  iodine  number  represents  the  number  of  centigrams  of  iodine 
absorbed  by  1  gram  of  oil,  i.e.,  the  percentage  of  iodine  absorbed. 


242  TECHNICAL  METHODS  OF  ANALYSIS 

Wijs  Solution.— (I)  Dissolve  separately  7.9  grams  of  iodine 
trichloride  and  8.7  grams  of  iodine  in  glacial  acetic  acid  on  a 
water  bath,  taking  particular  care  that  the  solutions  do  not 
absorb  water;  then  pour  both  solutions  into  a  liter  volumetric 
flask,  rinsing  the  containers  with  glacial  acetic  acid;  make  up  to 
the  mark  with  glacial  acetic  acid  and  mix  thoroughly.  Or, 

(2)  Dissolve  13.0  grams  of  resublimed  iodine  in  1  liter  of  c.  p. 
glacial  acetic  acid.  Titrate  a  portion  with  0.1  N  thiosulfate. 
Set  aside  about  25  cc.  Into  the  remainder  pass  washed  and 
dried  chlorine  gas  until  the  original  thiosulfate  titration  is  just 
doubled.  Then  add  the  small  portion  of  original  solution  to 
neutralize  any  free  chlorine.  Preserve  in  amber-colored  glass- 
stoppered  bottles. 

NOTES. — (1)  It  is  very  necessary  that  the  chlorine  gas  be  passed  through 
cone.  H2SO4  to  dry  it,  as  moisture  spoils  the  solution. 

(2)  Wijs  solution  should  not  be  used  after  it  is  more  than  one  month  old. 

Acid  Number  (Total  Fatty  Acids) . — Weigh  20  grams  of  sample 
into  a  300  cc.  Erlenmeyer  flask.  Add  50  cc.  of  95%  alcohol  pre- 
viously neutralized  with  0.1  NaOH  and  phenolphthalein.  Heat 
to  the  boiling  point  on  the  steam  bath,  agitate  the  flask  thoroughly, 
and  titrate  with  0.1  N  KOH  (or  NaOH),  shaking  thoroughly  until 
the  pink  color  persists.  The  add  number  is  expressed  as  milli- 
grams of  KOH  required  per  1  gram  of  oil. 

CALCULATION.— 1  cc.  0.1  N  KOH  =  5.61  mg.  KOH. 

In  case  the  percentage  of  fatty  acids  is  desired,  use  the  follow- 
ing factor:  1  cc.  0.1  N  KOH  =  0.02824  gram  oleic  acid. 

It  may  be  noted  that  the  percentage  of  oleic  acid  X  1.99  =  acid 
number. 

Soluble  Fatty  Acids. — This  determination  is  made  on  the  solu- 
tion after  titrating  for  the  saponification  number.  Place  the 
flask  on  the  water  bath  and  evaporate  off  the  alcohol.  Add  suf- 
ficient 0.5  N  HC1  so  that  its  volume,  plus  the  amount  used  in 
titrating  for  the  saponification  number,  will  be  1  cc.  in  excess  of 
the  amount  required  to  neutralize  the  50  cc.  of  alcoholic  KOH 
added.  Place  on  the  steam  bath  until  fatty  acids  separate  into 
a  clear  layer.  Fill  to  the  neck  with  hot  water  and  cool  in  ice 
water  until  the  cake  of  fatty  acids  is  thoroughly  hardened.  Pour 
the  liquid  contents  of  the  flask  through  a  filter  into  a  liter  flask. 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        243 

Fill  the  flask  again  with  hot  water,  and  set  on  the  steam  bath  until 
the  fatty  acids  collect  on  the  surface.  Cool  by  immersion  in 
ice  water  and  again  filter  the  liquid  into  the  liter  flask.  Repeat 
this  treatment  with  hot  water  3  times,  cooling  and  collecting  the 
washings  in  the  liter  flask  after  each  treatment.  Titrate  the  com- 
bined washings  with  0.1  N  NaOH  and  phenolphthalein.  Sub- 
tract 5  (which  corresponds  to  the  excess  of  1  cc.  of  0.5  N  HC1) 
from  the  number  of  cc.  of  0.1  N  NaOH  used.  The  difference 
multiplied  by  0.00881  gives  the  weight  of  soluble  acids,  as  butyric 
acid.  Calculate  to  percentage. 

Insoluble  Fatty  Acids  (Hehner  Number.) — Drain  the  flask 
containing  the  cake  of  insolub'e  fatty  acids  from  the  previous 
determination  and  the  paper  through  which  the  soluble  fatty  acids 
have  been  filtered,  and  dry  for  twelve  hours.  Transfer  the  cake, 
with  as  much  of  the  fatty  acids  as  can  be  removed  from  the  filter 
paper,  to  a  weighed  wide-mouthed  beaker  flask.  Then  place  the 
funnel  containing  the  filter  in  the  neck  of  the  flask  and  wash  the 
paper  thoroughly  with  hot  absolute  alcohol.  Remove  the  fun- 
nel, evaporate  off  the  alcohol,  dry  for  two  hours  at  100°  C.,  cool 
in  a  desiccator  and  weigh.  Again  dry  for  two  hours,  cool  and 
weigh.  If  there  is  any  considerable  decrease,  re-heat  for  two  hours 
and  weigh  again.  Calculate  the  final  weight  to  percentage  of 
insoluble  fatty  ac  ds. 

Soluble  Volatile  Fatty  Acids  (Reichert-Meissl  Number).— 
This  method  is  of  particular  value  in  the  case  of  substances 
containing  butter  fat,  which  has  a  very  high  Reichert-Meissl 
number.  As  the  determination  is  entirely  empirical,  it  is  neces- 
sary to  follow  the  directions  exactly. 

REAGENTS.— (1)  NaOH  solution  (1:1).— The  NaOH  should 
be  as  free  as  possible  from  carbonates.  Protect  the  solution  from 
contact  with  CO2.  Let  it  settle  and  use  only  the  clear  liquid. 

(2)  KOH  Solution  —Dissolve  100  grams  of  purest  KOH  in 
58  cc.  of  hot  water.    Cool  in  a  stoppered  vessel,  decant  the 
clear  solution  and  protect  from  contact  with  CO2. 

(3)  95%  Alcohol  by  Volume.— Distilled  over  NaOH. 

(4)  Dilute  H2S04.— Dilute  200  cc.  of  cone.  H2SO4  to  1  liter 
with  water. 

(5)  Barium    (or   Sodium)    Hydroxide   Solution. — Standardize 
an  approximately  0.1  N  solution. 


244  TECHNICAL  METHODS  OF  ANALYSIS 

(6)  Indicator. — Dissolve  1  gram  of  phenolphthalein  in  100  cc. 
of  95%  alcohol. 

(7)  Pumice  Stone. — Heat  small  pieces  to  white  heat,  plunge 
in  water,  and  keep  under  water  until  used. 

SAPONIFICATION.— Weigh  5.75  cc.  (about  5  grams)  of  filtered 
sample  into  a  300  cc.  Erlenmeyer  flask;*  add  10  cc.  of  95% 
alcohol  and  2  cc.  of  NaOH  solut  on  and  heat  on  the  steam  bath 
under  a  reflux  condenser  (a  glass  tube  not  less  than  3  feet  long  may 
be  used)  until  saponification  is  complete  as  shown  by  clear  solu- 
tion. After  saponification,  remove  the  alcohol  by  evaporation 
on  the  steam  bath.  Avoid  possible  loss  near  the  end  by  removing 
the  flask  and  waving  it  back  and  forth  in  the  air.  Remove  the 
last  traces  of  alcohol  by  a  stream  of  air  free  from  CO2. 

DISTILLATION  AND  TITRATION. — Dissolve  the  soap  obtained 
above  by  adding  135  cc.  of  recently  boiled  water  and  warm  on  the 
water  bath,  with  occasional  shaking,  until  the  solution  is  clear. 
Cool  to  60-70°  C.,  add  5  cc.  of  the  dil.  H2SO4,  stopper  loosely 
and  heat  on  the  water  bath  until  the  fatty  acids  form  a  clear 
transparent  layer,  which  may  take  several  hours.  Cool  to  room 
temperature,  add  a  few  pieces  of  pumice  stone  and  connect  with  a 
glass  condenser  by  means  of  a  bulb  tube.  Heat  slowly  with  a 
free  flame  until  ebullition  begins  and  distill,  regulating  the  flame 
so  as  to  collect  110  cc.  of  distillate  in  as  nearly  thirty  minutes  as 
possible.  Mix  this  distillate,  filter  through  a  dry  filter,  and  titrate 
100  cc.  with  standard  barium  or  sodium  hydroxide  solution,  using 
phenolphthalein  indicator.  The  red  color  should  persist  for 
two  to  three  minutes. 

Multiply  the  number  of  cc.  of  0.1  N  alkali  used  by  1.1,  divide 
by  the  weight  of  fat  taken  and  multiply  by  5  to  obtain  the  Reich- 
ert-Meissl  number.  Correct  the  result  by  the  figure  obtained 
in  a  "  blank  "  determination. 

Insoluble  Volatile  Fatty  Acids  (Polenske  Number). — For  this 
determination  use  the  method  described  in  J.  Assoc.  Official 
Agr.  Chemists.  Methods  of  Analysis  (1916),  page  308. 

Acetyl  Value. — Boil  the  sample  (10-50  grams,  depending  on  its 
nature)  with  an  equal  volume  of  acetic  anhydride  in  an  acetyliza- 

*  The  fat  should  be  warmed  if  necessary  to  melt  it.  Use  a  warm  Mohr 
pipette  for  measuring  out  the  liquid  fat  into  the  flask,  taking  care  to  wipe  off 
the  adhering  fat  and  to  prevent  any  fat  getting  on  the  sides  of  the  flask.  Let 
come  to  room  temperature  and  weigh  accurately. 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS         245 


tion  flask  for  two  hours;  pour  the  mixture  into  a  large  beaker 
containing  500  cc.  of  water  and  boil  for  thirty  minutes.  To 
prevent  bumping,  pass  a  slow  current  of  CCb  into  the  liquid 
through  a  finely  drawn  out  tube  reaching  nearly  to  the  bottom. 
Let  the  mixture  separate  into  two  layers,  siphon  off  the  water, 
and  boil  the  oily  layer  with  fresh  water  until  it  is  no  longer  acid  to 
litmus.  Separate  the  acetylated  fat  from  water,  filter  and  dry  at 
105°  C. 

Weigh  2-4  grams  of  the  acetylatep!  fat  into  a  300  cc.  Erlen- 
meyer  flask  and  saponify  with  an  excess  of  alcoholic  KOH  as 
described  under  Saponification  Number,  measuring  the  alcoholic 
KOH  solution  exactly.  Evaporate  the  alcohol  after  saponifica- 
tion  and  dissolve  the  soap  in  water.  Then  add  to  the  soap  solu- 
tion a  quantity  of  standard  H2S04  exactly  corresponding  to  the 
amount  of  alcoholic  KOH 
added;  warm  gently,  filter  off 
the  free  fatty  acids  which  col- 
lect on  top,  wash  with  boiling 
water  until  the  washings  are  no 
longer  acid  and  titrate  the  fil- 
trate with  0.1  N  KOH  and 
phenolphthalein.  Multiply  the 
number  of  cc.  of  alkali  by 
5.61  and  divide  by  the  weight 
of  acetylated  oil  used,  to  obtain 
the  acetyl  value. 

Melting  Point. — Determine 
the  melting  point  by  the  closed 
capillary  tube  method.  Draw 
the  melted  sample  into  a  thin- 
walled  capillary  tube.  Use  a 
column  of  fat  1-2  cm.  long, 
according  to  the  length  of  the 
thermometer  bulb.  Seal  one 
end  of  the  tube  and  cool  on  ice 
twelve  to  fifteen  hours.  Attach  FIG.  14.— Melting  Point  Apparatus, 
the  capillary  tube  with  a  rub- 
ber elastic  to  the  bulb  of  an  accurate  thermometer;  immerse 
in  a  large  test  tube  of  water  surrounded  by  a  beaker  of  water, 


246  TECHNICAL  METHODS  OF  ANALYSIS 

and  heat  very  slowly.  An  apparatus  similar  to  that  shown 
in  Fig.  14  may  be  used.  Record  the  temperature  at  which  the 
fat  becomes  transparent  as  its  melting  point. 

NOTE. — In  legal  cases  and  cases  of  dispute  use  the  Wiley  metnod  as 
described  in  J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis  (1916), 
page  301. 

liter  Test. — (A)  ALCOHOLIC  OR  AQUEOUS  NAOH  METHOD. — 
(1)  Standard  thermometer. — The  thermometer  must  have  a  zero 
mark,  0.1°  graduations  between  10°  and  60°  C.,  and  auxiliary 
reservoirs  at  the  upper  end  and  between  the  0°  and  10°  marks. 
The  cavity  in  the  capillary  tube  between  the  0°  and  10°  marks 
must  be  at  least  1  cm.  below  the  10°  mark,  which  must  be  about 
3-4  cm.  above  the  bulb,  the  total  length  of  the  thermometer  being 
about  38  cm.  The  bulb  should  be  about  3  cm.  long  and  6  mm.  in 
diameter.  The  stem  of  the  thermometer  should  be  6  mm.  in  diam- 
eter and  made  of  the  best  thermometer  tubing,  with  the  scale 
etched  on  the  stem,  graduations  clear  cut  and  distinct.  The 
thermometer  should  have  been  annealed  for  seventy-five  hours  at 
450°  C.,  and  the  bulb  should  be  Jena  normal  16"1  glass,  mod- 
erately thin,  so  that  the  thermometer  will  be  quick-acting. 

(2)  Determination. — Saponify  75  grams  of  the  sample  in  a 
metal  dish  with  60  cc.  of  30%  NaOH  solution  (36°  Be.)  and  75  cc. 
of  95%  alcohol  by  volume  or  120  cc.  of  water.  Evaporate  to  dry- 
ness  over  a  very  low  flame  or  on  an  iron  or  asbestos  plate,  stirring 
constantly.  Dissolve  the  dry  soap  in  1  liter  of  boiling  water  and, 
if  alcohol  has  been  used,  boil  for  forty  minutes  to  remove  it,  adding 
sufficient  water  to  replace  that  lost  in  boiling.  Liberate  the  fatty 
acids  by  adding  100  cc.  of  30%  H2SO4  (25°  Be.)  and  boil  until  they 
form  a  clear,  transparent  layer.  Wash  with  boiling  water  until 
free  from  H2S04,  collect  in  a  small  beaker  and  place  on  the  steam 
bath  until  the  water  has  settled  and  the  fatty  acids  are  clear; 
then  decant  into  a  dry  beaker,  filter  while  hot  and  dry  twenty 
minutes  at  100°  C.  When  dried,  cool  the  fatty  acids  to  15- 
20°  C.  above  the  expected  titer  and  transfer  to  a  titer  tube,  25  by 
100  mm.  (1  by  4  inches)  and  made  of  glass  about  1  mm.  in  thick- 
ness. Place  in  a  16-ounce  wide-mouthed  bottle  of  clear  glass,  70 
by  150  mm.  (2.8  by  6  inches)  fitted  with  a  perforated  cork  so  as 
to  hold  the  tube  rigidly  when  in  position.  Suspend  a  standard 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        247 

thermometer  so  that  it  can  be  used  as  a  stirrer,  and  stir  the  mass 
slowly  until  the  mercury  remains  stationary  for  thirty  seconds. 
Then  let  the  thermometer  hang  quietly,  with  the  bulb  in  the 
center  of  the  mass,  and  observe  the  rise  of  the  mercury  column. 
The  highest  point  to  which  it  rises  is  regarded  as  the  titer  of  the 
fatty  acids.  The  titer  test  must  be  made  at  about  20°  C.  for  all 
fats  having  a  titer  above  30°  C.  and  at  10°  C.  below  the  titer  for 
all  others. 

Test  the  fatty  acids  for  complete  saponification  as  follows: 
Place  3  cc.  in  a  test  tube  and  add  15  cc.  of  95%  alcohol  by  volume. 
Bring  the  mixture  to  boiling  and  add  an  equal  volume  of  dil. 
NH40H.  A  clear  solution  should  result. 

(B)  GLYCEROL-KOH  METHOD. — Heat  75  cc.  of  glycerol-KOH 
solution  (25  grams  KOH  in  100  cc.  of  high-test  glycerol)  to  150°  C. 
in  an  800  cc.  beaker;  then  add  50  cc.  of  the  oil  or  melted  fat,  pre- 
viously filtered  if  necessary  to  remove  foreign  substances.  Sapon- 
ification often  takes  place  almost  immediately,  but  heating  with 
frequent  stirring,  should  be  continued  for  fifteen  minutes,  avoiding 
a  temperature  much  above  150°  C.  When  saponification  is  com- 
plete, as  indicated  by  a  perfectly  homogeneous  solution,  pour  the 
soap  solution  into  an  800  cc.  casserole  containing  about  500  cc.  of 
nearly  boiling  water,  add  carefully  50  cc.  of  30%  H^SCU  and  heat 
the  solution,  with  frequent  stirring,  until  the  layer  of  fatty  acids 
separates  out  perfectly  clear.  Transfer  the  fatty  acids  to  a  tall 
separatory  funnel,  wash  3-4  times  with  boiling  water  to  remove 
all  mineral  acids,  draw  the  fatty  acids  off  into  a  small  beaker,  and 
let  stand  on  the  steam  bath  until  the  water  has  settled  out  and  the 
acids  are  clear.  Filter  into  a  dry  beaker  and  heat  to  150°  C. 
on  a  thin  asbestos  plate,  stirring  continually  with  the  thermometer; 
transfer  to  the  titer  tube,  fill  it  to  within  2.5  cm.  of  the  top  and 
determine  the  titer  as  directed  above. 

SPECIAL  TESTS 

Cholesterol  and  Phytosterol  (in  Mixtures  of  Animal  and  Vege- 
table Fats). — Introduce  200-300  grams  (accurately  weighed,  if  a 
determination  of  unsaponifiable  matter  is  desired)  of  melted  fat 
into  a  flat-bottomed  liter  flask.  Close  the  neck  of  the  flask  with  a 
3-hole  stopper  and  insert  through  these  holes:  (1)  a  reflux  con- 
denser; (2)  a  right-angled  glass  tube,  one  arm  of  which  reaches  to 


248  TECHNICAL  METHODS  OF  ANALYSIS 

a  point  6  mm.  above  the  surface  of  the  melted  fat,  the  other  being 
closed  a  short  distance  from  the  flask  by  means  of  a  short  piece  of 
rubber  tubing  and  a  pinch-cock;  (3)  a  glass  tube  bent  so  that 
one  arm  reaches  down  to  the  bottom  of  the  flask  and  the  other 
serves  as  a  delivery  tube  for  a  700  cc.  round-bottomed  flask  con- 
taining 500  cc.  of  95%  alcohol  by  volume. 

Place  the  flasks,  containing  the  melted  fat  and  alcohol,  respect- 
ively, on  a  steam  bath  and  heat  so  that  the  alcohol  vapor  passes 
through  the  melted  fat  in  the  liter  flask  and  is  condensed  in  a 
reflux  condenser,  finally  collecting  in  a  layer  over  the  melted  fat. 
After  all  the  alcohol  has  passed  in  this  manner  into  the  flask 
containing  the  fat,  disconnect  the  flask  from  which  the  alcohol 
has  been  distilled  and  attach  the  tube  to  a  short  piece  of  rubber 
tubing  attached  to  a  right-angled  glass  tube  (as  in  (2)  above) 
and  siphon  the  alcohol  layer  back  into  the  alcohol  distillation 
flask.  Re-connect  as  at  first  and  again  distill  the  alcohol  as  in 
the  first  operation.  When  all  alcohol  has  been  distilled,  siphon 
it  again  into  the  distillation  flask  and  extract  in  the  same  manner 
for  the  third  time. 

Discard  the  fat  and  retain  the  alcohol  which  now  contains  • 
practically  all  of  the  cholesterol  and  phytosterol  originally  pres- 
ent in  the  fat.  Concentrate  the  alcoholic  solution  to  about  250 
cc.  and  add  20  cc.  of  KOH  solution  (1  :  1)  to  the  boiling  liquid. 
Boil  for  ten  minutes  to  insure  complete  saponification  of  the  fat, 
cool  to  room  temperature  and  pour  into  a  large  separatory  funnel 
containing  500  cc.  of  warm  ether.  Shake  to  insure  thorough  mix- 
ing and  add  500  cc.  of  water.  Rotate  the  funnel  gently  to  avoid 
the  formation  of  persistent  emulsions,  but  mix  the  water  thor- 
oughly with  the  alcohol-ether-soap  solution.  A  clear,  sharp 
separation  takes  place  at  once.  Draw  off  the  soap  solution  and 
wash  the  ether  layer  with  300  cc.  of  water,  avoiding  shaking. 
Repeat  the  washing  of  the  ether  solution  with  small  quantities 
of  water  until  all  soap  is  removed.  Transfer  the  ether  layer  to  a 
flask  and  distill  the  ether  until  the  volume  of  the  liquid  remaining 
in  the  flask  is  about  25  cc.  Transfer  this  residue  to  a  tall  50  cc. 
beaker  and  continue  evaporation  until  all  ether  is  driven  off  and 
the  residue  is  perfectly  dry.* 

*  If  desired,  a  tared  beaker  may  be  used  and  the  weight  of  unsaponifiable 
matter  determined  at  this  point. 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS         249 

Add  3-5  cc.  of  acetic  anhydride  to  the  residue  in  the  beaker, 
cover  with  a  watch-glass  and  heat  to  boiling  over  a  free  flame. 
After  boiling  for  a  few  seconds,  remove  the  beaker  from  flame, 
cool  and  add  35  cc.  of  60%  alcohol  by  volume.  Mix  the  contents 
of  the  beaker  thoroughly,  filter  off  the  alcoholic  solution  and  wash 
the  precipitate  with  60%  alcohol.  Dissolve  the  precipitate  on 
the  filter  with  a  stream  of  hot  80%  alcohol  by  volume  and  wash 
the  insoluble  portion  well  with  80%  alcohol.  Acetates  of  choles- 
terol and  phytosterol  are  dissolved,  while  the  greater  portion  of 
the  impurities  present  (including  paraffin  oil  if  present)  remains 
behind  on  the  filter.  Cool  the  combined  filtrate  and  washings  to  a 
temperature  of  10-12°  C.  and  let  stand  at  that  temperature  for 
two  to  three  honrs.  During  this  time  the  acetates  of  cholesterol 
and  phytosterol  crystallize  from  solution.  Collect  the  crystals 
on  a  filter,  wash  with  cold  80%  alcohol  and  then  dissolve  them  in  a 
minimum  amount  of  hot  absolute  alcohol.  Collect  the  alcoholic 
solution  of  acetates  in  a  small  glass  evaporating  dish,  add  2  or  3 
drops  of  water  to  the  solution  and  heat  if  not  perfectly  clear.  Let 
the  alcohol  evaporate  spontaneously,  the  contents  of  the  dish 
being  stirred  occasionally  to  mix  with  the  main  body  of  liquid 
the  deposit  of  crystals  which  forms  upon  the  edges.  As  soon 
as  a  good  deposit  of  crystals  has  formed,  collect  them  upon  a 
hardened  filter,  wash  twice  with  cold  90%  alcohol  and  dry  by 
suction,  drying  finally  at  100°  C.  for  thirty  minutes,  and  determine 
the  melting  point  in  the  apparatus  shown  in  Fig.  14,  using  H^SCU 
in  the  outer  beaker  and  glycerol  in  the  inner  tube. 

The  melting  point  of  the  first  crop  of  crystals  usually  gives 
definite  information  as  to  the  presence  or  absence  of  phytosterol 
but  the  conclusion  indicated  should  be  confirmed  by  re-crystallizing 
the  crystals  from  absolute  alcohol  and  again  determining  their 
melting  point.  If  the  crystals  are  pure  cholesteryl  acetate,  the 
melting  point  of  the  second  crop  should  agree  closely  with  that  of 
the  first.  If  phytosteryl  acetate  is  present,  however,  a  higher 
melting  point  will  be  noted,  as  phytosteryl  acetate  is  less  soluble 
in  alcohol  than  cholesteryl  acetate.  The  melting  point  of  choles- 
teryl acetate  is  114°  C.,  that  of  phytosteryl  acetate  is  125-137°  C. 

Qualitative  Test  for  Rosin  Oil.— Polarize  the  pure  oil,  or  a 
definite  dilution  with  petroleum  ether,  in  a  200  mm.  tube.  Rosin 
oil  has  a  polarization,  in  a  200  mm.  tube,  of  from  +30°  to  +40° 


250  TECHNICAL  METHODS  OF  ANALYSIS 

on  the  sugar  scale  (Schmidt  and  Haensch),  while  most  other  oils 
read  between  +1°  and  — 1°. 

Halphen  Test  for  Cottonseed  Oil. — Mix  €82  containing  about 
1%  of  sulfur  in  solution,  with  an  equal  volume  of  amyl  alcohol. 
Mix  equal  volumes  of  this  reagent  and  the  oil  sample  and  heat  in  a 
bath  of  boiling,  saturated  brine  for  one  to  two  hours.  This  is 
conveniently  accomplished  in  an  acetylization  flask.  In  the 
presence  of  as  little  as  1%  of  cottonseed  oil,  a  characteristic  red 
or  orange-red  color  is  produced. 

Lard  and  lard  oil  from  animals  fed  on  cottonseed  meal  will  give 
a  faint  reaction;  their  fatty  acids  also  give  this  reaction. 

The  depth  of  color  is  proportional,  to  a  certain  extent,  to  the 
amount  of  cottonseed  oil  present,  and  by  making  comparative 
tests  with  cottonseed  oil  some  idea  as  to  the  amount  present  can  be 
obtained.  Different  oils  react  with  different  intensities,  and  oils 
which  have  been  heated  from  200-210°  C.  react  with  greatly 
diminished  intensity.  Heating  for  ten  minutes  at  250°  C.  renders 
cottonseed  oil  incapable  of  giving  the  reaction. 

NOTES. — (1)  Blown  cottonseed  oil  and  old  rancid  oil  cannot  be  identified 
by  this  test. 

(2)  Kapok  and  Baoban  oils  also  give  similar  color  reactions. 

(3)  A  blank  test  should  always  be  conducted  under  the  same  conditions 
on  a  pure  sample  of  the  oil  being  tested  and  also  on  a  pure  oil  to  which  has  been 
added  a  little  cottonseed  oil. 

Tests  for  Peanut  Oil. — (A)  RENARD  TEST. — Weigh  20  grams 
of  oil  into  an  Erlenmeyer  flask.  Saponify  with  alcoholic  KOH 
solution,  neutralize  exactly  with  dilute  acetic  acid  and  phenol- 
phthalein  and  wash  into  an  800-1000  cc.  flask  containing  a  boiling 
mixture  of  100  cc.  of  water  and  120  cc.  of  20%  lead  acetate  solution. 
Boil  for  a  minute  and  then  cool  the  precipitated  soap  by  immersing 
the  flask  in  water,  occasionally  giving  it  a  whirling  motion  to  cause 
the  soap  to  stick  to  the  sides  of  the  flask.  After  the  flask  has 
cooled,  decant  the  water  and  excess  of  Pb  acetate  solution  and 
wash  the  Pb  soap  with  cold  water  and  then  90%  alcohol  by  vol- 
ume. Add  200  cc.  of  ether,  cork  and  let  stand  for  some  time 
until  the  soap  is  disintegrated.  Heat  on  the  water  bath  with  a 
reflux  condenser,  and  boil  for  five  minutes.  In  the  case  of  oils, 
most  of  the  soap  will  be  dissolved;  with  lards,  which  contain 
much  stearin,  part  of  the  soap  will  be  left  undissolved.  Cool  the 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS         251 

ether  solution  of  soap  to  15-17°  C.  and  let  stand  until  all  insoluble 
soaps  have  separated  out  (about  twelve  hours). 

Filter  upon  a  Biichner  funnel  and  thoroughly  wash  the  insoluble 
Pb  soaps  with  ether.  Wash  the  ether-insoluble  Pb  soaps  into  a 
separatory  funnel  by  means  of  a  jet  of  ether,  alternating  at  the 
end  of  the  operation,  if  the  soaps  stick  to  the  paper,  with  HC1 
(1  :  3).  Add  sufficient  HC1  (1  :  3)  so  that  the  total  volume  of 
the  latter  amounts  to  about  200  cc.  and  enough  ether  to  make  its 
total  volume  150-200  cc.  and  shake  vigorously  for  several  minutes. 
Let  the  layers  separate,  run  off  the  acid  layer,  and  wash  the  ether 
once  with  100  cc.  of  dil.  HC1  and  then  with  several  portions  of 
water  until  the  water  washings  are  no  longer  acid  to  methyl 
orange.  If  a  few  undecomposed  lumps  of  Pb  soap  remain  (indi- 
cated by  solid  particles  remaining  after  the  third  washing  with 
water),  break  these  up  by  running  off  almost  all  the  water  layer 
and  then  add  a  little  cone.  HC1;  shake  and  then  continue  washing 
with  water  as  before.  Distill  the  ether  from  the  solution  of  insol- 
uble fatty  acids  and  dry  the  latter  in  the  flask  by  adding  a  little 
absolute  alcohol  and  evaporating  on  the  steam  bath.  Dissolve 
the  dry  fatty  acids  by  warming  with  100  cc.  of  90%  alcohol  by 
volume  and  cool  slowly  to  15°  C.,  shaking  to  aid  crystalliza- 
tion. Let  stand  at  15°  C.  for  thirty  minutes.  In  the  presence 
of  peanut  oil,  crystals  of  arachidic  acid  will  separate  from  solution. 

Filter  and  wash  the  precipitate  twice  with  10  cc.  of  90%  alcohol 
by  volume,  and  then  with  70%  alcohol  by  volume,  taking  care 
to  maintain  the  arachidic  acid  and  wash  solution  at  a  definite 
temperature  in  order  to  apply  solubility  corrections  given  below. 
Dissolve  the  arachidic  acid  upon  the  filter  with  boiling  absolute 
alcohol,  evaporate  to  dryness  in  a  weighed  dish,  dry  and  weigh. 
Add  to  the  weight  0.0025  gram  for  each  10  cc.  of  90%  alcohol  used 
in  the  crystallization  and  washing,  if  conducted  at  15°  C.;  if 
conducted  at  20°  C.,  add  0.0045  gram  for  each  10  cc.  The  melting 
point  of  arachidic  acid  thus  obtained  is  71-72°  C.  Twenty  times 
the  weight  of  arachidic  acid  will  give  the  approximate  amount 
of  peanut  oil  present.  Arachidic  acid  has  a  characteristic  appear- 
ance and  may  be  identified  microscopically.  As  little  as  5-10% 
of  peanut  oil  can  be  detected  by  this  method. 

It  is  best  to  run  a  "  blank  "  on  pure  peanut  oil  along  with  the 
test. 


252  TECHNICAL  METHODS  OF  ANALYSIS 

(B)  BELLIER  TEST.  * — Weigh  1  gram  of  the  sample  into  a  long 
test-tube.  Add  5  cc.  of  alcoholic  KOH  solution.  Boil  gently 
over  a  small  flame  holding  the  tube  in  the  hand  until  saponifica- 
tion  is  complete,  as  shown  by  homogeneous  solution  (generally 
three  to  five  minutes).  Add  the  proper  amount  of  acetic  acid 
(see  below)  to  exactly  neutralize  the  5  cc.  of  alcoholic  KOH. 
Mix  well,  cool  rapidly  in  water  at  about  17°  C.  and  let  stand  in 
the  water  for  at  least  thirty  minutes,  shaking  occasionally.  Then 
add  50  cc.  of  70%  alcohol  containing  1%  by  volume  of  cone.  HC1 
and  again  place  in  the  water  for  one  hour.  If  no  peanut  oil  is 
present,  a  clear  or  opalescent  liquid  is  formed.  If  more  than 
10%  of  peanut  oil  is  present,  a  flocculent,  crystalline  precipitate 
remains.  Even  with  5%  of  peanut  oil  a  distinct  precipitate 
remains  and  separates  on  standing. 

SOLUTIONS. — (1)  Alcoholic  KOH:  Dissolve  8.5  grams  of  pure  KOH  in 
70%  alcohol,  and  dilute  to  100  cc.  with  the  alcohol. 

(2)  Acetic  Acid:  This  should  be  of  such  strength  that  1.5  cc.  will  exactly 
neutralize  5  cc.  of  the  above  solution.  The  dilute  acetic  acid  reagent  (4 : 10) 
is  approximately  the  correct  strength  but  should  be  tested  against  the  alcoholic 
KOH. 

Tests  for  Sesame  Oil.— (A)  BAUDOUIN  TEST.— Dissolve  0.1 
gram  of  sugar  in  10  cc.  of  cone.  HC1  in  a  test  tube.  Add  20  cc.  of 
the  sample  to  be  tested.  Shake  thoroughly  for  one  minute. and 
let  stand.  The  aqueous  solution  separates  almost  immediately 
and  in  the  presence  of  even  minute  quantities  of  sesame  oil  it  is 
colored  crimson. 

(B)  VILLAVECCHIA  AND  FABEis  TESTS. — The  original  test  as 
proposed  by  Baudouin  has  been  modified  by  Villavecchia  and 
Fabris  and  is  usually  carried  out  according  to  one  of  the  following 
modifications : 

(1)  Place  0.1  cc.  of  a  2%  alcoholic  solution  of  furfural  in  a 
test-tube.     Add  10. cc.  of  the  oil  and  10  cc.  of  cone.  HC1.     Shake 
one-half  minute  and  let  settle.     In  the  presence  of  even  1%  of 
sesame  oil  the  aqueous  layer  is  a  distinct  crimson  color,  and 
in  the  absence  of  sesame  oil  the  lower  layer  is  either  colorless  or 
at  most,  in  the  case  of  rancid  pure  olive  oils,  a  dirty  yellow  color. 

(2)  Mix  0.1  cc.  of  2%  alcoholic  furfural  solution  with  10  cc.  of 
the  oil  and  add  1  cc.  of  cone.  HC1.     Agitate  thoroughly  and  add 

*  Allen:  "Commercial  Organic  Analysis,"  4th  edition,  Vol.  2,  99. 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS         253 

10  cc.  of  CHCls.     The  aqueous  layer  will  float  on  top  and  in 
the  presence  of  sesame  oil  will  be  colored  crimson. 

NOTE. — We  have  found  that  this  method  produces  a  slight  coloration  with 
certain  olive  oils  claimed  to  be  pure.  Furthermore,  the  oils  in  question  gave 
negative  results  by  the  Bellier  reaction  described  below. 

(C)  BELLIER  TEST.* — To  50  cc.  of  water,  add  100  cc.  of  cone. 
H2S04,  cool  and  add  10  cc.  of  40%  formaldehyde  solution.  Mix 
equal  parts  of  the  oil  and  the  above  reagent  by  stirring.  In  the 
presence  of  sesame  oil  the  emulsion  slowly  becomes  colored  a  very 
intense,  stable  blue-black.  With  olive  oil,  peanut  oil,  cottonseed 

011  and  walnut  oil,  the  emulsion  produced  is  more  or  less  yellow. 

It  is  stated  that  the  per  cent  of  sesame  oil  can  be  detected  with 
this  reaction  when  working  with  a  comparatively  pure  olive  oil. 
With  olive  oil  containing  2%  of  sesame  oil  the  color  of  the  emul- 
sion is  a  rather  dark  gray  after  five  or  ten  minutes.  The  acid 
which  separates  is  a  blackish  brown.  With  5%  of  sesame  oil,  the 
mixture  becomes  a  very  dark  black  gray  and  the  acid  which  sep- 
arates is  black  tinged  with  blue. 

Emery  Test  for  Beef  Fat  in  Lard. — Weigh  5  grams  of  melted 
fat  into  a  glass-stoppered  25  cc.  cylinder  about  150-175  mm.  tall. 
Add  warm  ether  up  to  the  25  cc.  mark,  stopper  securely  and  shake 
until  the  fat  is  completely  dissolved.  Let  the  cylinder  stand  for 
about  eighteen  hours  at  a  temperature  of  16-20°  C.,  during  which 
time  some  of  the  solid  glycerides  will  crystallize  out.  Decant 
the  clear  solution  carefully  from  the  crystals,  wash  with  three 
5  cc.  portions  of  cold  ether,  avoiding  breaking  up  the  deposit 
during  the  first  two  washings.  Agitate  the  crystals  with  a  third 
portion  of  ether  and  transfer  to  a  small  filter.  Wash  on  the 
paper  with  successive  small  amounts  of  cold  ether  until  15-20  cc. 
have  been  used,  then  remove  the  last  traces  of  ether  by  means  of 
slight  suction  on  the  stem  of  the  funnel.  Break  up  any  large 
lumps  and  let  the  deposit  dry. 

When  thoroughly  dry,  pulverize  the  glycerides  and  take  their 
melting  point  in  a  closed  1  mm.  tube,  using  an  apparatus  similar  to 
that  in  Fig.  14 f,  page  245.     Heat  the  water  in  the  beaker  rapidly  to 
about  55°  C.  and  maintain  that  temperature  until  the  thermometer 
carrying  the  melting-point  tube  registers  50-55°  C.,  then   heat 
*  Ann.  chim.  anal.,  1899,  page  217. 
t  Page  245. 


254  TECHNICAL  METHODS  OF  ANALYSIS 

again  and  carry  the  temperature  of  the  outer  bath  somewhat 
rapidly  to  67°  C.,  and  remove  the  lamp.  The  melting  point 
of  the  crystals  is  regarded  as  that  point  where  the  fused  substance 
becomes  perfectly  clear  and  transparent.  A  dark  background 
placed  about  4  inches  from  the  apparatus  will  prove  of  advantage. 
When  the  melting  point  of  the  glycerides  obtained  by  this  method 
is  below  63.4°  C.,  the  presence  of  beef  fat  should  be  suspected, 
while  a  melting  point  of  63°  C.  or  below,  can  be  regarded  as  posi- 
tive evidence  that  the  sample  is  not  pure  lard.  It  is  advisable  to 
carry  out  this  method  with  a  control  sample  of  pure  lard  in  con- 
nection with  each  batch  of  samples  analyzed. 

Fish  and  Marine  Animal  Oils  in  Vegetable  Oils. — This  test  is 
only  applicable  in  the  absence  of  metallic  salts. 

Dissolve  in  a  test  tube  about  6  grams  of  sample  in  12  cc.  of  a 
mixture  of  equal  parts  of  CHCls  and  glacial  acetic  acid.  Add 
bromine  drop  by  drop,  until  a  slight  excess  is  indicated  by  the 
color,  keeping  the  solution  at  about  20°  C.  Let  stand  fifteen 
minutes  or  more  and  then  place  the  test  tube  in  boiling  water. 
If  vegetable  oils  only  are  present,  the  solution  will  become  per- 
fectly clear,  while  fish  oils  will  remain  cloudy  or  contain  a  precip- 
itate due  to  the  presence  of  insoluble  bromides. 

REFERENCE. — J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis 
(1916),  pages  299-315. 

LUBRICATING  OILS 

Gravity. — The  gravity  of  lubricating  oils  is  generally  deter- 
mined as  degrees  Baume.  Take  the  gravity  by  means  of  a  Baume 
hydrometer  if  possible.  If  the  oil  is  too  light  for  this,  use  a 
Westphal  balance.  In  the  case  of  thick  oils,  use  a  hydrometer 
and  let  it  remain  in  the  oil  at  least  one-half  hour,  so  that  it  will 
sink  as  far  as  possible.  Use  a  cylinder  sufficiently  large  so  that 
the  hydrometer  does  not  touch  the  sides,  and  also  use  a  sufficient 
volume  of  oil  so  that  the  hydrometer  does  not  come  nearer  than 
within  0.5  inch  of  the  bottom  when  at  rest.  Take  the  reading  of 
the  hydrometer  at  the  point  where  the  lower  meniscus  of  the  oil 
touches  the  scale.  If  the  oil  is  not  too  thick,  bring  it  to  exactly 
60°  F.  before  reading  the  hydrometer  or  balance;  otherwise 
determine  the  temperature  of  the  oil  at  the  time  of  reading  the 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        255 

hydrometer  and  correct  the  reading  to  60°  F.  (15.5°  C.).  Taglia- 
bue's  "  Manual  for  Inspectors  of  Coal  Oil  "  gives  readings  at  60°  F. 
for  any  gravity  from  20-100°  Baume  between  20°  F.  and  109°  F. 

In  using  the  Westphal  balance,  be  sure  that  the  plummet  is 
completely  submerged  and  does  not  touch  the  sides  or  bottom  of 
the  cylinder  containing  the  oil.  Have  the  temperature  of  the  oil 
at  60°  F.  From  the  sp.  gr.  found  by  the  balance  the  gravity 
Baume  may  be  calculated  from  the  formula: 

141  5 

Baume  =  - 131.5°.* 

sp.  gr. 

NOTE. — The  Westphal  balance  should  be  leveled  so  that  the  plummet  in 
air  just  balances  the  arm  at  zero.  If  the  weights  are  accurate  the  reading  in 
distilled  H2O  at  60°  F.  should  be  1.0000.  In  case  the  reading  in  H2O  is  differ- 
ent from  this,  correct  the  observed  reading  on  the  sample  by  dividing  it  by 
the  reading  of  the  balance  in  water. 

Flash  Point. — For  lubricating  oils  use  the  Cleveland  open-cup 
tester.  The  apparatus  consists  of  a  spun  brass  or  cast-iron  cup, 
1.38  inches  high  by  2.5  inches  in  diameter,  in  ah  air  bath  heated 
from  below  by  a  Tirrill  burner.  Fill  the  cup  with  oil  to  within 
about  j  inch  of  the  top.  Use  an  accurate  Fahrenheit  thermometer 
scaled  for  l^inch  immersion.  Immerse  the  thermometer  in  the 
center  of  the  oil  at  sufficient  depth  so  that  the  surface  of  the  oil  is  at 
the  1-inch  mark.  The  rate  of  heating  should  be  10°  F.  per  minute. 
At  intervals  of  about  2°,  when  approaching  the  flash  point,  sweep  a 
tiny  flame  not  more  than  0.5  inch  long  slowly  and  steadily  across 
the  cup  at  a  distance  of  about  f  inch  from  the  surface  of  the  oil. 
Take  as  the  flash  point  the  first  point  at  which  a  puff  of  blue  flame 
appears  and  runs  round  the  cup  and  then  goes  out. 

Fire  Points — Continue  heating  after  the  flash  point  has  been 
determined,  applying  the  test  flame  at  intervals  of  2°.  Take  as 
the  fire  point  the  point  at  which  the  oil  will  just  take  fire  and  con- 
tinue to  burn.  This  varies  from  15-80°  higher  than  the  flash 
point,  depending  upon  the  nature  of  the  oil. 

*  This  is  the  formula  used  in  making  Tagliabue  hydrometers.  The  U.  S. 
Bureau  of  Standards  employs  the  formula : 

140° 

Baume  =— 130°. 

sp.  gr. 


256  TECHNICAL  METHODS  OF  ANALYSIS 

NOTE. — It  is  important  that  the  rate  of  heating  should  be  even  and  the  test 
flame  should  not  be  played  directly  upon  the  surface  of  the  oil,  since  that  will 
cause  local  superheating.  The  apparatus  must  be  carefully  protected  from 
drafts. 

Cloud  Test. — The  cloud  test  indicates  the  temperature  at 
which  solid  matter  crystallizes  out.  Cut  off  the  neck  and  shoul- 
der of  a  4-ounce  oil  bottle  and  fill  one-quarter  full  of  the  oil,  or 
sufficient  to  reach  0.25  inch  above  the  bulb  of  the  thermometer. 
The  thermometer  used  is  the  so-called  "  cloud  test  thermometer," 
especially  made  for  testing  oils,  with  a  bulb  J-f  inches  long. 
Insert  the  thermometer  through  a  perforated  cork  so  that  it  is 
held  centrally  in  the  bottle  with  the  lower  end  of  the  bulb  0.5 
inch  from  the  bottom.  Then  place  the  whole  in  a  metal  or  glass 
jacket  4-5  inches  high,  having  an  inside  diameter  0.5  inch  larger 
than  the  outside  diameter  of  the  oil  bottle.  Place  a  disc  of  felt, 
cork,  or  wax  0.25  inch  thick  in  the  bottom  of  the  jacket.  The 
inner  bottle  must  not  touch  the  sides  of  the  jacket  at  any  point. 
Then  place  the  whole  apparatus  in  a  freezing  mixture  and  at  every 
drop  in  temperature  of  2°  F.,  when  near  the  expected  cloud  test, 
remove  the  oil  bottle  from  the  jacket  and  inspect  it,  taking  care 
not  to  disturb  the  oil  by  removing  the  thermometer  or  otherwise. 

When  the  lower  half  of  the  sample  becomes  opaque  through 
chilling,  read  the  thermometer.  This  reading  shall  be  taken  as 
the  cloud  test  of  the  sample. 

NOTE. — If  the  oil  contains  any  water,  misleading  results  will  be  obtained. 
It  should,  therefore,  be  heated  momentarily  to  150°  C.  and  then  cooled  imme- 
diately before  making  the  test. 

Pour  Test. — The  "  pour  test "  indicates  the  temperature  at 
which  the  oil  will  just  flow.  In  making  this  test  the  same  bottle 
and  quantity  of  oil  are  used  as  for  the  cloud  test  and  it  may  be 
made  immediately  after  the  cloud  test.  In  practically  all  cases 
the  cloud  test  is  higher  than  the  pour  test. 

Place  the  sample  in  the  oil  bottle  in  the  jacket  as  previously 
described  and  put  the  whole  in  a  freezing  mixture.  At  each  drop 
in  temperature  of  5°  F.  remove  the  bottle  from  the  jacket,  and 
incline  until  the  oil  begins  to  flow.  Do  not  tilt  the  bottle  any  more 
than  necessary  to  determine  if  the  oil  will  flow.  Finally  the 
bottle  should  be  held  at  horizontal.  When  the  oil  has  become 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        257 

solid  about  the  thermometer  and  will  not  flow,  the  previous  5° 
point  shall  be  taken  as  the  pour  test  of  the  sample. 

NOTES. — (1)  The  cold  should  preferably  be  applied  so  that  the  pour  test 
shall  be  completed  in  about  0.5  hour. 

(2)  Materials  used  in  the  freezing  mixture  may  be  ice  with  calcium  chloride 
crystals  or  salt,  or  solid  CO2  with  acetone. 

For  oils  solidifying  above  35°  F.  use  cracked  ice;  from  +35°  to  +15°  use 
finely  cracked  ice  with  about  5%  its  volume  of  salt;  from  +15°  to  —5°  use 
one  part  salt,  3  parts  ice.  The  salt  should  be  very  dry  and  fine  enough  to 
pass  a  20-mesh  sieve.  It  is  possible  to  reach  —  25°  F.  with  a  mixture  of  ice  and 
calcium  chloride  crystals,  but  for  temperatures  below  —5°  it  is  better  to  use 
solid  CO2  and  acetone  as  follows: 

Take  a  sufficient  amount  of  dry  acetone  and  put  it  into  a  covered  copper  or 
Pyrex  beaker.  Place  the  beaker  in  an  ice-salt  mixture,  and  when  cooled  to 
+10°  F.  or  lower,  add  solid  CO2,  little  by  little,  until  the  desired  temperature 
is  reached.  Solid  CO2  is  obtained  by  inverting  an  ordinary  liquefied  CO2 
cylinder;  open  the  valve  carefully  and  let  the  gas  run  out  into  a  chamois  or 
canvas  bag.  Temperatures  of  —80°  F.  may  be  reached  by  this  method. 

Cold  Test. — Use  the  oil  cylinder  as  described  in  the  Cloud  Test. 
Add  to  it  1  ounce  of  oil  (28  cc.).  Place  the  oil  in  the  bottle  directly 
in  the  freezing  mixture  (see  note  (2)  above)  and  freeze  solid  with  a 
cold  test  thermometer  immersed  in  it.  When  the  oil  has  become 
solid  throughout,  let  stand  one-half  hour.*  Remove  the  bottle 
from  the  freezing  mixture.  Stir  the  oil  thoroughly,  as  soon  as  it 
has  become  soft  enough  to  permit,  grasping  the  bottle  in  such  a 
way  that  the  heat  of  the  hand  does  not  warm  the  oil.  Continue 
stirring,  tipping  the  bottle  up  at  frequent  intervals  to  an  angle  of 
45°  below  the  horizontal,  and  note  the  temperature  at  which  the 
oil  will  just  run  from  one  end  of  the  bottle  to  the  other.  This 
point  is  taken  as  the  cold  test. 

NOTES. — (1)  To  get  comparative  results  the  above  directions  should  be 
followed  exactly,  and  even  in  this  case  there  is  a  considerable  personal  factor 
entering  into  the  determination. 

(2)  The  4-ounce  oil  bottles  used  should  be  cut  off  as  near  the  neck  as  pos- 
sible, each  one  having  a  mark  on  the  side  indicating  how  much  oil  is  to  be  taken 
for  the  cold  test.  Determine  the  position  of  this  mark  by  placing  28  cc.  of 
water  in  the  bottle  and  making  a  mark  at  the  upper  surface  of  the  water.  Be 
sure  the  bottle  is  on  a  perfectly  level  place  when  the  mark  is  made. 

*  The  oil  should  be  cooled  to  at  least  10°  below  its  cold  test.  If,  therefore, 
the  cold  test  is  first  found  to  be  near  the  temperature  to  which  the  oil  has  been 
cooled  for  0.5  hour,  repeat  the  test,  first  cooling  the  oil  10°  lower  for  0.5  hour. 


258  TECHNICAL  METHODS  OF  ANALYSIS 

Viscosity. — Viscosity  determinations  are  to  be  made  with  the 
Saybolt  Universal  Viscosimeter.  The  temperature  is  generally 
specified  for  different  grades  of  oils.  Unless  otherwise  requested, 
the  following  temperatures  are  to  be  employed: 

212°  F.— Calender,  Crane,  Crank  Case,  Cylinder  and  Valve 
Oils. 

130°  F. — Black  (Dark  Lubricating  Oil),  Air  Compressor  and 
Journal  Oils. 

100°  F. — Automobile,  Crusher,  Cutting,  Dynamo,  Engine, 
Froth,  Governor,  Loom,  Machinery,  Shafting,  Sperm,  Spindle, 
Transformer,  Turbine,  and  Whale  Oils. 

MANIPULATION. — Have  the  viscosimeter  level.  Bring  the  water 
bath  of  the  viscosimeter  to  the  required  temperature.  Strain 
the  oil  through  muslin  into  a  tin  cup  and  heat  in  the  cup  to  the 
required  temperature,  stirring  with  the  thermometer.  Clean  out 
the  tube  of  the  instrument  with  some  of  the  strained  oil  to  be 
tested,  using  the  plunger. 

Place  the  cork  in  the  lower  outlet  coupling  tube  just  far  enough 
to  make  it  air-tight  but  not  far  enough  to  nearly  touch  the  small 
outlet  jet  of -the  tube  proper.  Between  J  and  \  inch  should  be 
enough.  Pour  the  heated  oil  from  the  tin  cup  through  the  strainer 
into  the  tube  of  the  viscosimeter  until  it  overflows  into  the  oil  cup 
up  to  and  above  the  upper  edge  of  the  tube  proper.  Again  note 
that  the  water  bath  is  at  the  proper  temperature.  Stir  the  oil 
in  the  upper  tube  with  the  thermometer  until  it  is  exactly  at  the 
correct  temperature,  then  remove  the  thermometer  and  draw 
off  from  the  overflow  tube  with  a  pipette  all  surplus  oil  down  to 
and  below  the  upper  edge  of  the  inner  tube.  This  always  insures 
the  same  starting  head  of  oil.  Place  the  60  cc.  flask  beneath  and 
directly  in  line  with  the  outlet  jet  and  as  close  to  the  tube  as  is 
practical  to  permit  of  room  for  drawing  the  cork.  Hold  a  stop 
watch  in  the  left  hand,  and  with  a  twisting  motion  remove  the 
cork  quickly  with  the  right  hand,  starting  the  watch  simultaneously. 
Note  the  exact  instant  at  which  the  oil  rises  to  the  60  cc.  mark  in 
the  flask,  and  stop  the  watch.  The  time  elapsed  for  60  cc.  of  oil 
to  flow  from  the  viscosimeter  is  its  viscosity  at  the  given  tempera- 
ture. Express  results  in  seconds. 

NOTES. — (1)  Before  each  test  clean  out  the  tube  of  the  instrument  with 
some  of  the  oil  to  be  tested,  and  before  removing  the  cork  note  that  the  oil 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS         259 

and  bath  are  at  the  proper  temperature  and  that  the  60  cc.  flask  is  free 
from  oil. 

(2)  The  Universal  instrument  is  not  intended  to  be  used  on  oils  at  tem- 
peratures below  100°  F. 

Saponifiable  Oil. — Ordinarily  this  determination  is  unnecessary, 
except  on  cylinder  oils  or  other  compounded  oils.  It  should 
always  be  run  in  duplicate. 

For  cylinder  oils  and  other  heavy  dark-colored  oils  weigh 
out  two  portions  of  about  20  grams  each  into  300  cc.  Erlen- 
meyer  flasks,  add  to  each  flask  25  cc.  of  approximately 
0.5  N  alcoholic  KOH,  accurately  delivered  from  a  pipette,  and 
50  cc.  of  pure  benzene.  Into  another  similar  clean  flask  add  from 
the  same  pipette  25  cc.  of  alcoholic  KOH  solution  and  50  cc.  of 
benzene  for  a  "  blank."  Connect  the  flasks  to  reflux  condensers 
and  boil  gently  with  a  low  flame  for  at  least  sixteen  hours,  agitating 
occasionally.  The  agitation  is  important  to  insure  mixing  and 
prevent  caking.  Then  remove  the  flasks  and  add  to  each  100  cc. 
of  distilled  water.  Cool,  and  titrate  each  with  0.5  N  acid  and 
phenolphthalein  until  the  pink  color  disappears  permanently. 
From  the  titration  required  by  the  "  blank  "  subtract  the  titra- 
tions  required  by  each  of  the  other  solutions,  respectively.  The 
difference  represents  the  amount  of  KOH  absorbed  by  the  saponi- 
fiable  oil.  Report  the  saponification  value  (milligrams  of  KOH 
per  gram  of  oil)  and  also  the  per  cent  of  saponifiable  oil. 

CALCULATION.— 1  cc.  0.5  N  acid  =  28.06  mg.  KOH. 

=  0.1439  gram  tallow  oil. 

NOTES. — (1)  The  above  details  are  for  heavy  cylinder  oils  containing  up  to 
10%  of  tallow  oil.  Lighter  oils  do  not  need  to  saponify  so  long,  and  the  ben- 
zene may  be  omitted.  The  blank  in  this  case  should  have  benzene  omitted. 
For  a  light  cutting  oil  one  or  two  hours  is  sufficient.  For  oils  containing 
more  than  10%  saponifiable  use  less  than  20  grams  for  the  determination. 
With  a  little  experience  the  analyst  can  judge  about  how  much  oil  to  weigh 
out  and  how  long  to  saponify  it. 

(2)  It  is  customary  to  calculate  the  saponifiable  oil  to  tallow  oil  (saponifi- 
cation value  195)  although  sometimes  other  oils  are  used.  With  the  exception 
of  wool  grease,  however,  their  saponification  numbers  are  approximately  the 
same  and  the  above  calculations  will  show  the  amount  present.  In  the  case 
of  wool  grease  (average  saponification  value  102)  the  following  factor  should 
be  used: 

1  cc.  0.5  N  acid  =  0.275  gram  wool  grease. 

Wool  grease  may  be  recognized  by  its  characteristic  odor  on  heating.  If, 
in  compounding  the  oil,  a  mixture  of  wool  grease  and  some  other  fatty  oil  is 


260  TECHNICAL  METHODS  OF  ANALYSIS 

employed,  it  is  impossible  by  analysis  to  determine  the  relative  proportions, 
and  the  titration  should  be  calculated  both  as  wool  grease  and  as  tallow  oil. 
The  actual  amount  present  will  lie  between  these  figures. 

(3)  The  saponification  may  be  conducted  in  pressure  flasks  instead  of  by 
the  above  procedure.     In  this  case  weigh  the  sample  into  the  pressure  flask, 
add  the  alcoholic  potash  (but  not  benzene),  clamp  tightly  and  place  the  flasks 
in  a  steam  or  hot  water  bath.     Eight  hours  is  sufficiently  long  for  a  cylinder  oil. 
A  blank  should  be  run  in  a  separate  pressure  flask. 

(4)  In  the  case  of  oils  containing  wool  grease  the  saponification  should 
always  be  conducted  in  a  pressure  flask  to  obtain  accurate  results,  as  by  the 
ordinary  method  it  is  very  difficult  to  completely  saponify  the  wool  grease. 

Residue  Insoluble  in  Gasoline. — Unless  otherwise  specified 
carry  out  this  test  on  cylinder  oils  as  follows:  Shake  5  cc.  of  the  oil 
with  100  cc.  of  ordinary  gasoline  and  let  stand  for  one  hour.  There 
should  be  no  deposit  or  precipitation  of  tarry  or  other  foreign 
matter. 

The  quantitative  estimation  is  carried  out  as  follows:  Weigh 
out  approximately  5  grams  of  oil  into  a  small  beaker.  Transfer 
by  means  of  86°  naphtha  to  a  100  cc.  graduated  cylinder.  Fill 
to  the  mark  with  86°  naphtha.  Agitate  several  times  until  oil 
and  naphtha  are  thoroughly  mixed.  Stopper  and  let  stand  for 
whatever  time  is  specified  (generally  one  hour).  Filter  through  a 
filter  paper  which  has  been  dried  at  100°  C.  for  two  hours,  cooled 
and  weighed.  Wash  the  cylinder  out  with  86°  naphtha  and  pour 
the  washings  through  the  filter  paper.  Wash  the  paper  thoroughly 
with  the  naphtha  to  remove  all  traces  of  oil.  Dry  in  the  air 
and  then  at  100°  C.,  cool  in  a  desiccator  and  weigh.  (If  desired 
it  may  then  be  ignited  and  weighed  to  determine  the  amount  of 
mineral  matter,  dirt,  etc.) 

NOTE. — 86°  naphtha  is  highly  inflammable  and  must  not  be  used  in  the 
same  room  with  any  flame. 

Mineral  Acid. — Weigh  25-50  grams  of  oil  into  a  500  cc.  sepa- 
ratory  funnel,  add  300  cc.  of  hot  distilled  water,  recently  boiled, 
and  shake  thoroughly.  Titrate  the  water  while  still  hot  with  0. 1  N 
caustic  and  phenolphthalein.  Run  a  blank  on  the  same  amount  of 
hot  water  and  subtract  the  blank  titration  from  the  previous. 
Calculate  the  difference  to  H2SO4. 

CALCULATION. — 1  cc.  of  0.1  N  caustic  =  0.0049  gram  H2SO4. 

REFERENCES. — Gill:  "Oil  Analysis."  Lewkowitsch:  "Chemical  Tech- 
nology and  Analysis  of  Oils,  Fats  and  Waxes,"  Vol.  1.  American  Society  for 
Testing  Materials,  Tentative  Standards,  1917. 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        261 


UNSAPONIFIABLE  MATTER  IN  OILS 

General. — The  determination  of  unsaponifiable  matter  in  oils 
falls  into  2  general  classes, — (1)  mineral  oil  in  mixtures  of  mineral 
and  fatty  oils,  (2)  the  natural  unsaponifiable  matter  occurring  in 
animal  and  vegetable  oils. 

The  method  which  would  give  satisfactory  results  for  the  first 
class  is  hardly  sufficiently  accurate  to  be  applied  to  the  determina- 
tion of  the  small  amount  of  unsaponifiable  matter  in  the  second 
class.  Of  the  two  methods  given  below  the  first  is  applicable  in 
all  cases  except  where  a  very  accurate  determination  of  the  un- 
saponifiable matter  naturally  occurring  in  animal  or  vegetable 
oils  is  desired. 

Method  1. — Weigh  out  3-5  grams  of  the  sample  into  a 
300  cc.  Erlenmeyer  flask,  add  50  cc.  of  0.5  N  alcoholic  KOH  and 
saponify  under  a  reflux  condenser  for  several  hours.  Add  a  few 
drops  of  phenolphthalein  to  make  sure  that  there  is  an  excess  of 
alcoholic  KOH.  In  case  there  is  not  an  excess,  add  25  cc.  more 
and  resaponify.  Transfer  the  contents  of  the  flask  to  a  beaker 
and  evaporate  off  the  bulk  of  the  alcohol  on  the  steam  bath. 
Dissolve  the  residual  soap  in  about  50  cc.  of  hot  water  and  transfer 
to  a  separatory  funnel,  using  about  20-30  cc.  of  water  for  rinsing 
the  beaker.  The  total  volume  should  be  kept  below  100  cc.  to 
minimize  the  tendency  to  form  emulsions.  Cool,  and  add  50  cc. 
of  ether  and  shake  thoroughly.  If  the  solution  does  not  separate 
well,  add  a  few  cc.  of  alcohol.  Run  off  the  lower  soap  solution 
into  another  separatory  funnel  and  shake  this  out  with  a*  fresh 
portion  of  50  cc.  of  ether.  Repestt  the  process  once  again.  Com- 
bine the  3  ethereal  extracts  and  wash  twice  with  about  15  cc.  of 
water  to  remove  any  dissolved  soap.  Transfer  the  washed 
extracts  to  a  weighed  Soxhlet  flask,  distill  off  the  ether  on  the 
water  bath  and  dry  the  residue  at  100°  C.  to  constant  weight. 

NOTES. — (1)  If  it  is  suspected  that  the  unsaponifiable  matter  is  contam- 
inated with  soap,  dissolve  it  in  ether.  Transfer  to  a  porcelain  or  platinum 
dish,  evaporate  off  the  ether  and  ash  the  residue.  Then  titrate  the  ash  with 
0.1  N  acid  and  methyl  orange  and  calculate  the  amount  of  soap  present. 

CALCULATION. — 1  cc.  0.1  N  acid  =  0.0320  gram  potash  soap. 

(2)  Troublesome  emulsions  sometimes  form  during  extraction.  In  such 
cases  it  will  be  found  convenient  to  add  a  little  alcohol  or  glycerol  after  shaking, 


262  TECHNICAL  METHODS  OF  ANALYSIS 

and  then  impart  a  slight  rotary  movement  to  the  separately  funnel  without, 
however,  agitating  it.  In  other  cases  the  addition  of  a  little  NaOH  will  break 
up  the  emulsion.  Sometimes  a  flocculent  layer  will  appear  between  the  ether 
solution  and  the  solvent.  This,  however,  does  not  interfere  with  the  correct 
determination  of  the  unsaponifiable  matter  and  should  be  drawn  off  and  con- 
sidered as  soap. 

Another  method  of  breaking  emulsions  is  to  apply  suction.  Insert  a  one- 
hole  stopper  with  a  glass  tube  in  the  neck  of  the  funnel  and  apply  suction 
gently,  increasing  slowly  until  the  ether  boils.  Care  should  be  taken  not  to 
boil  the  ether  too  violently  and  to  avoid  sucking  back  when  the  suction  is 
released. 

(3)  86°  petroleum  ether  may  be  used  in  place  of  ordinary  ether,  but,  on 
account  of  the  danger  of  high  boiling  non-volatile  constituents,  it  is  not  rec- 
ommended. In  certain  cases,  however,  notably  with  tallow,  petroleum  ether 
fails  to  extract  all  the  unsaponifiable  matter. 

Method  2  (Boemer).— To  100  grams  of  oil  in  a  1000-1500  cc. 
Erlenmeyer  flask  add  60  cc.  of  an  aqueous  solution  of  KOH 
(200  grams  dissolved  in  water  and  made  up  to  300  cc.)  and 
140  cc.  of  95%  alcohol.  Connect  with  a  reflux  condenser  and  heat 
on  the  water  bath,  shaking  at  first  until  the  liquid  becomes  clear. 
Then  heat  for  one  hour  with  occasional  shaking.  Transfer  while 
yet  warm  to  a  2000  cc.  separately  funnel,  to  which  some  water 
has  been  added,  and  wash  out  the  Erlenmeyer  flask  with  water, 
using  in  all  600  cc.  Cool)  add  800  cc.  of  ether  and  shake  vigorously 
for  one  minute.  In  a  few  minutes  the  ether  solution  separates  per- 
fectly clear.  Draw  off  the  soap  and  filter  the  ether  (to  remove  the 
last  traces  of  soap)  into  a  large  Erlenmeyer  flask  and  distill  off  the 
ether,  adding,  if  necessary,  one  or  two  pieces  of  pumice  stone.  Shake 
the  soap  solution  three  times  with  400  cc.  of  ether,  which  add  to  the 
first  ether  extract.  To  the  residue  left  after  distilling  the  ether 
add  3  cc.  of  the  above  KOH  somtion,  and  7  cc.  of  95%  alcohol, 
and  heat  under  a  reflux  condenser  for  ten  minutes  on  the  water 
bath.  Transfer  to  a  small  separatory  funnel,  using  20-30  cc.  of 
water  and,  after  cooling,  shake  out  with  2  portions  of  100  cc.  of 
ether.  Wash  the  ether  3  times  with  10  cc.  of  water.  After  draw- 
ing off  the  last  of  the  water,  filter  the  ethereal  solution  so  as  to 
remove  the  last  drops  of  water,  distill  off  the  ether,  and  dry  the 
residue  in  a  water  oven  to  constant  weight  at  100°  C. 

REFERENCES. — Lewkowitsch:  ''  Chemical  Technology  and  Analysis  of 
Oils,  Fats  and  Waxes,"  Vol.  1,  pages  364-367;  Boemer-Ubbelohde :  "  Hand- 
buch  der  Ole  u.  Fette,"  pages  261-2. 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        263 


CASTOR  OIL 

General. — Pure  castor  oil  is  nearly  colorless  or  pale  greenish, 
very  viscous  and  of  high  sp.  gr.  It  has  also  a  very  high  acetyl 
value,  and  is  strongly  dextrorotary.  Its  saponification  value  is 
comparatively  low.  It  is  miscible  in  all  proportions  with  glacial 
acetic  acid  and  with  absolute  alcohol.  The  "  constants  "  of  a  pure 
oil  should  come  within  the  following  limits: 

Sp.  gr.  at  15.5°  C 0.958-0.970 

Saponification  number 176-187 

Iodine  number .  81-91 

Acetyl  value about  150 

Free  fatty  acid about  1% 

Analysis. — The  procedures  for  the  determination  of  each  of  the 
above  constants  are  given  on  pages  230-244. 

Solubility  Tests. — (a)  In  glacial  acetic  acid. 

(6)  In  absolute  alcohol. 

Mix  in  2  test  tubes  equal  parts  of  the  sample  with  each  of  the 
above  reagents,  respectively.  In  each  case  the  oil  should  dissolve 
completely  and  show  no  turbidity. 

NOTE. — Castor  oil  is  generally  not  adulterated.  Adulteration  with 
blown  oils  (linseed,  rape,  cottonseed,  etc.)  would  be  detected  by  turbidity  in 
the  solubility  tests.  In  the-  case  of  suspected  addition  of  rosin  oil,  determine 
the  unsaponifiable  matter,  which  in  pure  castor  oil  is  less  than  1  %.  All  adul- 
terations would  lower  the  acetyl  value. 

SULFONATED  OILS 
(TURKEY  RED  OILS) 

General. — Sulfonated  oils  are  made  by  treating  various  oils 
with  H2SO4.  The  excess  of  acid  is  then  neutralized  with  alkali 
and  a  certain  amount  of  water  added.  Formerly  castor  oil  was 
supposed  to  give  a  better  sulfonated  oil  than  any  other  but  this  is 
now  open  to  dispute,  as  many  other  oils  have  been  sulfonated  and 
the  resulting  product  is  satisfactory  for  many  purposes.  Among 
them  may  be  mentioned  olive  oil,  maize  oil,  cottonseed  oil,  lard 
oil,  and  rosin  oil.  Sulfonated  rosin  oil  especially  has  found 
considerable  use  in  cutting  oils.  It  is  to  be  noted  that  the  amount 


264  TECHNICAL  METHODS  OF  ANALYSIS 

of  oil  in  commercial  sulfonated  oils  is  generally  considerably  over- 
stated. A  so-called  "  50%  oil  "  will  not  generally  contain  more 
than  40%  of  oil,  and  a  70%  oil  from  60-65%  of  oil,  etc. 

Moisture. — Weigh  out  30-40  grams  and  determine  the  moisture 
by  the  Xylol  method  as  described  on  page  271. 

Ash. — Weigh  any  convenient  quantity  into  a  dish  or  cru- 
cible, ignite  gently,  allowing  the  oil  to  burn,  and  finally  heat  until 
all  the  carbon  is  consumed.  Cool  in  a  desiccator  and  weigh. 

Unsaponifiable  Matter  (Mineral  Oil,  etc.). — Weigh  approx- 
imately 10  grams  into  a  300  cc.  Erlenmeyer  flask.  Add  5  cc.  of 
KOH  solution  (50  grams  of  KOH  dissolved  in  H20  and  diluted 
to  100  cc.),  then  45  cc.  of  ethyl  alcohol  and  a  few  glass  beads. 
Boil  for  one  hour  with  a  reflux  condenser.  Add  100  cc.  of  water 
and  cool,  transfer  to  a  separatory  funnel  and  shake  out  at  least 
three  times  with  petroleum  ether  (naphtha),  using  50  cc.  each  time. 
Wash  the  ether  layer  at  least  three  times  with  50  cc.  of  water  con- 
taining 10  cc.  of  ethyl  alcohol.  If  emulsions  are  formed,  add  a 
little  alcohol  to  break  them.  Finally  evaporate  the  petroleum 
ether  extract  in  a  tared  vessel,  dry,  cool  and  weigh. 

NOTE. — The  petroleum  ether  should  have  a  boiling  point  of  40-75°  C.  and 
should  leave  no  residue  when  evaporated  on  the  steam  bath.  During  the 
saponification,  if  the  contents  of  the  flask  bump  violently,  turn  out  the  flame 
and  let  the  solution  cool,  and  then  add  25  cc.  of  the  petroleum  ether  and  con- 
tinue the  boiling. 

Free  Sulfur  Trioxide. — Weigh  out  approximately  4  grams 
into  a  separatory  funnel,  add  sufficient  petroleum  ether  to  dissolve 
it  and  shake  out  several  times  with  25  cc.  portions  of  a  cone. 
NaCl  solution,  free  from  sulfates.  Combine  the  washings,  dilute, 
filter  and  determine  the  SOs  in  the  filtrate  (salt  solution)  in  the 
usual  way  with  BaCl2,  finally  weighing  as  BaSCU.  Calculate  to 
S03. 

CALCULATION.— BaS04  X  0.3430  =  SO3. 

Combined  Sulfur  Trioxide. — Weigh  approximately  4  grams 
into  an  Erlenmeyer  flask  and  boil  forty  minutes  with  30  cc.  of 
HC1  (1  :  5).  Shake  frequently,  cool,  transfer  to  a  separatory 
funnel  and  shake  out  with  petroleum  ether.  Draw  off  the  aqueous 
layer  and  wash  the  ethereal  layer  with  water.  Combine  the 
washings  with  the  main  aqueous  portions,  let  the  petroleum 
ether  evaporate  spontaneously  until  the  odor  is  practically  gone 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        265 

and  then  heat  on  a  steam  bath.  Finally  transfer  to  a  flame, 
heat  to  boiling,  add  10  cc.  of  hot  10%  BaCb  solution,  boil  one- 
half  hour,  filter  out  the  BaSO4,  ignite  and  weigh.  Calculate  to 
80s.  This  gives  the  amount  of  total  SOs.  To  obtain  the  com- 
bined SOa,  subtract  the  free  SOa  as  previously  determined. 

Total  Fatty  Oil. — Calculate  the  total  fatty  oil  by  subtracting 
from  100%  the  sum  of  the  moisture,  ash  and  unsaponifiable 
matter. 

If  an  actual  determination  of  the  total  fatty  oil  is  desired, 
save  the  soap  solution  left  after  extracting  with  petroleum  ether  in 
the  determination  of  unsaponifiable  matter.  Add  an  excess  of 
HC1  to  it  and  shake  out  with  ether  three  times.  Wash  the  ether 
extracts  with  H^O,  evaporate  the  ether  in  a  tared  flask,  dry  and 
weigh  as  fatty  acids. 

NOTES. — (1)  Report  the  results  only  to  one  decimal  place. 

(2)  This  is  the  Provisional  Method  of  the  American  Leather  Chemists' 
Association. 

REFERENCE. — Journal  of  American  Leather  Chemists'  Association  14, 
668  (1919). 


LARD  OIL 

General. — Lard  oils  are  generally  graded  as  follows: 

1.  Prime  Lard  Oil. — Is  prepared  from  prime  steam  lard  and 
is  light  straw  colored.     Also  known  as  Extra  Winter   Strained. 
Acidity  is  low;  railroad  specifications  usually  allow  2%  oleic  acid. 

2.  Pure  Lard  Oil. — Also  a  light-colored  oil  made  from  No.  1 
lard  and  white  grease. 

3.  Extra  No.  1  Lard  Oil. — Somewhat  darker  oil  than  the  above; 
made  from  light  yellow  grease.     Specifications  generally  require 
not  over  10%  oleic  acid. 

4.  No.  1  Lard  Oil. — Deep  yellow;   made   from  yellow  grease. 
This  grade  varies  considerably;    the  oleic  acid  may  run  15%  or 
less,  or  may  go  as  high  as  20%. 

5.  No.  2  Lard  Oil. — Brown  colored,  prepared  from  brown  and 
gut  greases. 

6.  Crackling  Lard  Oil. — Cheapest  grade  and  made  from  crack- 
ling grease. 


266  TECHNICAL  METHODS  OF  ANALYSIS 

For  the  "  constants  "  of  pure  oil,  see  page  234. 

Specific  Gravity. — See  page  230. 

Saponification  Number. — See  page  241. 

Iodine  Number. — See  page  241. 

Free  Fatty  Acid.— See  page  242. 

Cold  Test. — When  it  is  desired  to  deterine  the  cold  test  use 
the  procedure  described  on  page  257.  Some  specifications  call 
for  a  cold  test  below  45°  F.  between  October  1st  and  May  1st. 

OLIVE  OIL 

General. — Olive  oil  is  obtained  from  the  fruit  of  the  olive  tree 
and  its  quality  depends  upon  the  care  with  which  it  is  prepared. 
The  best  grade  of  edible  oil  is  known  as  "  Virgin  Oil."  Lower  grade 
oils  are  frequently  known  as  "  Salad  Oil  "or  "  Ordinary  Table 
Oil."  A  still  lower  grade  is  used  for  soap-making.  The  color  varies 
considerably,  commercial  oils  being  of  shades  from  colorless  to 
yellow  and  the  lower  grades  generally  quite  green  due  to  dis- 
solved chlorophyll.  The  "  constants  "  vary  somewhat  with  the 
grade  of  oil  but  generally  are  within  the  following  limits : 

Sp.  gr.  at  15.5°  C 0.914-0.920* 

Saponification  number 185-200 

Iodine  number 77-  93 

Acetyl  value 5-30 

Unsaponifiable  matter 0 . 5-1 . 5% 

The  iodine  number  of  high-grade  oils  should  be  generally 
between  81  and  85  and  the  free  fatty  acid  less  than  1%. 

Several  tests  have  been  recommended  for  detection  of  mixtures 
of  other  oils  with  olive  oil.  Some  of  these  tests  depend  upon  the 
production  of  a  characteristic  color.  Such  tests,  however,  should  be 
used  with  caution  and  always  should  be  accompanied  by  a  blank 
test  on  olive  oil  of  known  purity  and  also  on  pure  olive  oil  con- 
taining varying  amounts  of  the  suspected  foreign  oil. 

Specific  Gravity,  Saponification  Number,  Iodine  Number,  and 
Free  Fatty  Acid.— See  pages  230-242. 

Elaidin  Test. — Place  in  a  test  tube  10  grams  of  the  oil,  5  grams 
of  cone.  HNOs  and  1  gram  of  mercury,  and  dissolve  the  latter 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        267 

by  shaking  continuously  three  minutes.  Let  the  mixture  stand 
for  twenty  minutes  and  again  shake  for  one  minute.  The  behavior 
of  different  oils  after  that  time  is  recorded  in  the  following  table: 

Kind  of  Oil.  Consistence. 

Olive  Solidified  after    60  minutes 

Arachis  (Peanut)  Solidified  after    80  minutes 

Sheep's  foot  Solidified  after  120  minutes 

Sesame  Solidified  after  185  minutes 

Colza  (Rape)  Solidified  after  185  minutes 

Linseed  Forms  red  dough-like  scum 

Cod  liver  Becomes  doughy,  red  and  forms  scum 

Whale  Remains  unchanged 

Hemp  seed  Remains  unchanged 

NOTES. — (1)  The  test  must  be  made  at  a  temperature  not  lower  than  25°  C. 
and  the  temperature  must  be  uniform  throughout  the  experiment. 

(2)  The  length  of  time  required  for  solidification  is  of  far  greater  importance 
than  the  ultimate  consistency  of  elaidin  formed. 

(3)  The  test  cannot  be  made  quantitative.     Also  the  age  of  the  oil  and 
the  length  of  time  it  has  been  exposed  to  air  and  light  have  an  important  bear- 
ing on  the  results.     It  is  necessary  to  carry  out  the  test  side  by  side  with  an 
oil  of  known  purity  under  exactly  similar  conditions. 

Maumene  Test. — Weigh  accurately  50  grams  of  the  oil  into  a 
250  cc.  beaker.  Have  ready  a  bottle  of  cone.  H2S04,  the  exact 
strength  of  which  has  been  determined  by  titration.  Place  the 
bottle  of  acid  and  the  beaker  of  oil  in  a  large  vessel  of  water  until 
both  have  acquired  the  same  temperature,  which  should  be  about 
20°  C.  Remove  the  beaker  of  oil,  wipe  the  outside  and  place  in  a 
"  nest  "  of  cardboard  having  hollow  sides  stuffed  with  cotton 
wool,  or  in  a  large  beaker  lined  with  cotton  wadding.  Immerse 
the  bulb  of  a  centigrade  thermometer  in  the  oil  and  note  the  tem- 
perature. Then  pipette  10  cc.  of  cone.  H2SO4  and  let  it  run 
rapidly  into  the  oil.  The  time  allowed  for  emptying  of  the  pipette 
should  be  only  one  minute.  During  this  time,  stir  the  oil  with  the 
thermometer  and  continue  stirring  until  no  further  rise  of  temper- 
ature is  observed.  The  highest  point  is  easily  noticed,  as  the  tem- 
perature remains  constant  for  some  little  time  before  it  begins  to 
fall. 

The  influence  of  the  concentration  of  the  acid  on  the  result  is 
shown  in  the  following  table: 


268 


TECHNICAL  METHODS  OF  ANALYSIS 


Kind  of  Oil 

Rise  of  Temperature  Observed  with  Acid 
Containing  Per  Cent  of  H2SO4 

97.38% 

96.71% 

95.72% 

94.72% 

93.75% 

92.73% 

91.85% 

Olive,  genuine.  .  .  . 

42.25 
43.25 

42 

39 

36.5 

34.50 

31 

28.00 
29.25 

Rape,  genuine.  .  .  . 

62 
63 

61 

58 

54 

50.25 

47 

40.5 
43.0 

Olive,  impure  .... 

48.5 

47.0 
47.5 

43.75 
44.25 

40.25 
40.75 

38.5 
39.0 

35.5 

32.5 

Color  Tests. — Halphen  Test  for  Cottonseed  Oil,  see  page  250. 

Baudoin  Test  for  Sesame  Oil,  see  page  252. 

Villavecchia  Test  for  Sesame  Oil,  see  page  252. 

Bellier  Test  for  Sesame  Oil,  see  page  253. 

Probable  Adulterants. — Cottonseed  Oil. — Shown  by  high  iodine 
value  (100-117),  high  Maumene  figure  (variously  given  from 
61-84),  and  positive  Halphen  Test. 

Peanut  Oil. — Shown  by  high  iodine  value  (96-109)  and  isola- 
tion of  arachidic  acid  by  Renard  Test  (see  page  250). 

Rape  Oil. — Shown  by  high  iodine  value  (94-105)  and  low 
saponification  value  (167-179). 

Sesame  Oil. — Shown  by  Baudoin  Test. 

Poppy-seed  Oil. — Shown  by  high  iodine  value  (134-142)  and 
high  Maumene  figure  (74-78). 

NOTE. — Olive  oil  is  characterized  by  low  Maumene  value  and  iodine  num- 
bers and  by  solid  elaidin. 

REFERENCES . — Gill :  "Oil  Analysis, ' '  5th  Edition .  Lewkowitsch :  ' ' Chem- 
ical Technology  and  Analysis  of  Oils,  Fats  and  Waxes."  Allen:  "  Commer- 
cial Organic  Analysis." 


TALLOW 

General. — Tallow  is  the  fat  of  beef  or  sheep.  There  is,  how- 
ever, very  little  pure  beef  or  mutton  tallow  on  the  market;  most 
tallow  is  a  mixture  of  the  two.  We  have  prepared  in  this  labora- 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        269 


tory  samples  of  pure  mutton  tallow  and  pure  beef  tallow  which, 
on  analysis,  showed  the  following  results: 


Mutton 

Beef 

Melting  point  (open  tube)      • 

50°  C. 

39°  C 

Iodine  number  (Wijs)  
Saponification  number               .... 

32 

198 

51 
198 

Free  fatty  acid  (as  oleic) 

0  48% 

1  16% 

Ash.                               

None 

None 

Moisture 

None 

None 

Color. — When  it  is  desired  to  determine  the  color,  melt  some  of 
the  sample  in  a  flat  Petri  dish  and  let  cool  quietly  so  that  it  will 
form  a  cake  with  a  smooth  flat  surface.  Measure  the  color 
with  the  Ives  colorimeter  or  tintometer,  specifying  in  the  report 
which  instrument  was  used. 

Melting  Point. — Determine  the  melting  point  by  the  open- 
tube  method.  Take  a  small  glass  tube  about  20  mm.  long  and 
1.5  mm.  inside  diameter,  open  at  both  ends.  Partly  fill  the  tube 
by  pushing  one  end  of  it  into  the  tallow.  Wipe  any  tallow  off  the 
outside  and  have  the  contents  flush  with  the  bottom  of  the  tube. 
Fasten  the  tube  to  the  mercury  bulb  of  a  thermometer  by  means  of 
rubber  elastics  and  suspend  the  thermometer  in  a  beaker  of  water. 
The  bottom  of  the  thermometer  should  be  0.5  inch  above  the 
bottom  of  the  beaker  and  there  should  be  sufficient  water  to  com- 
pletely cover  the  tube.  Heat  the  water  slowly  and  note  when  the 
tallow  just  begins  to  melt  and  draw  up  from  the  bottom  of  the 
tube.  Report  this  temperature  as  the  melting  point. 

Iodine  Number. — Weigh  out  0.4-0.5  gram  into  a  wide-mouth, 
glass-stoppered  bottle,  and  determine  the  iodine  number  by  the 
Wijs  method,  as  described  on  page  241. 

NOTE. — It  is  convenient  to  weigh  the  tallow  on  a  small  watch  crystal 
which  can  then  be  placed  directly  in  the  bottle. 

Saponification  Number. — Pour  about  2  grams  of  the  melted 
fat  into  a  weighed  Erlenmeyer  flask  of  about  300  cc.  capacity. 
Then  take  the  exact  weight  of  the  flask  and  tallow.  Determine 
the  Saponification  number  as  on  page  241. 


270  TECHNICAL  METHODS  OF  ANALYSIS 

Free  Fatty  Acid. — Weigh  10  grams  into  an  Erlenmeyer  flask  as 
above.  Add  60  cc.  of  ethyl  alcohol,  previously  neutralized  with 
0.1  N  caustic  and  phenolphthalein.  Warm  for  one-half  hour  on 
the  steam  bath  with  occasional  shaking.  Titrate  with  0.1  N 
caustic  and  phenolphthalein  with  vigorous  shaking  until  the  pink 
color  persists  for  one  minute.  Calculate  the  percentage  of  oleic 
acid. 

CALCULATION. — 1  cc.  of  0.1  N  caustic  =  0.0282  gram  oleic  acid. 

Moisture. — Melt  some  of  the  tallow  in  a  clean  dry  test  tube 
and  heat  until  it  begins  to  smoke.  If  any  appreciable  amount  of 
moisture  is  present  the  melted  fat  will  be  turbid  and  will  crackle. 
In  such  case,  determine  the  moisture  by  the  Xylol  Method  (see 
page  271). 

Ash. — Ignite  2-5  grams  gently  in  a  weighed  platinum  dish, 
cool  in  a  desiccator  and  weigh  the  ash  For  accurate  results  do 
not  let  the  fat  take  fire  and  burn. 

Soap. — Dissolve  the  ash  obtained  above  in  distilled  water 
and  titrate  with  0.1  N  HC1  and  methyl  orange.  Calculate  the 
titration  (if  any)  to  sodium  stearate. 

CALCULATION.— 1  cc.  0.1  N  acid  =^0.0306  gram  Na  stearate 
(soap). 

GREASES 

Types. — Commercial  greases  may  be  divided  into  the  follow- 
ing classes: 

A.  TALLOW  TYPE. — These  greases  are  made  up  of  tallow  and 
more  or  less  of  an  alkali  soap,  commonly  the  Na  or  K  soaps  of 
palm  oil,  mixed  with  a  smaller  amount  of  mineral  oil.     These 
were  the  principal  types  of  lubricating  grease  some  years  ago,  but 
to-day  are  less  used  than  the  greases  of  type  B. 

B.  SOAP-THICKENED  MINERAL  OIL  TYPE. — These  are  the  most 
common  journal  greases  to-day,  and  are  composed  of  mineral  oil 
of  various  grades  made  solid  by  the  addition  of  Ca  or  Na  soaps. 
The  former  soap  is  more  commonly  used. 

C.  PIGMENTED  GREASES.— Types  A  or  B  with  the  addition  of 
a  mineral  lubricant,  usually  graphite,  mica  or  talc. 

D.  ROSIN-OIL  TYPE. — These  consist  of  rosin  oil  thickened  by 
CaO,  or  less  commonly,  PbO,  to  which  is  added  more  or  less  min- 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS         271 

eral  oil,  either  paraffin  or  asphalt  oils  being  used.  These  are  sticky, 
usually  contain  20-30%  of  water,  and  find  their  chief  application 
as  gear  greases,  where  true  lubrication  is  not  so  essential  as  pre- 
vention of  wearing  and  rattling  of  the  gears.  Some  very  heavy 
bearings  are  occasionally  lubricated  with  this  type  of  grease. 
Tar,  pitch,  graphite  and  such  fillers  as  wood  pulp  and  ground  cork 
are  often  put  into  these  gear  greases. 

E.  NON-FLUID  OILS. — These  are  thin  greases  stiffened  to  some 
extent  with  aluminium  oleate  or  a  mixture  of  soaps,  as  for  instance 
Na  and  Ca  soaps. 

F.  SPECIAL  GREASES,  such  as  a  mixture  of  wood  pulp  and 
graphite ;  thin  greases  of  any  of  the  above  types  mixed  with  wool  or 
cotton  fibers;  freak  greases  containing  rubber,  etc. 

Of  the  above  types  A,  B,  and  C  are  the  most  important  as 
lubricants. 

General. — Note  first  the  odor  and  the  color.  The  grease 
should  melt  to  a  clear  homogeneous  fluid  and  the  oil  should  not 
melt  away  from  the  soap. 

Melting  Point. — For  a  grease  melting  below  100°  C.  use  an 
open  tube  with  an  interior  diameter  of  4  mm.  and  about  80  mm. 
long.  Plunge  this  into  the  sample  so  that  a  plug  of  grease  about 
1  cm.  long  is  left  in  the  glass  tube.  Then  attach  the  latter  by  a 
rubber  band  to  an  accurate  thermometer,  so  that  the  grease  is 
alongside  the  mercury  bulb.  Immerse  the  thermometer  with  the 
tube  attached  in  a  beaker  of  water  so  that  the  bottom  of  the  grease 
is  about  5  cm.  below  the  surface.  Heat  the  water  slowly  at  the 
rate  of  about  3-4°  C.  per  minute.  When  the  melting  point  is 
reached,  the  plug,  which  is  under  a  pressure  of  5  cm.  of  water,  will 
slide  up  in  the  tube. 

Moisture. — This  is  determined  by  the  so-called  Xylol  Method. 
Weigh  out  10  grams  of  the  grease  on  a  balanced  filter  paper  and 
place  the  grease  and  paper  in  a  300  cc.  Erlenmeyer  flask.  Add 
to  this  75  cc.  of  xylol  which  has  previously  been  saturated  with 
water,  as  follows: 

A  convenient  quantity  of  commercial  xylol,  say  500  cc.,  is 
shaken  up  in  a  separatory  funnel  with  water  and  the  xylol  drawn 
off  and  distilled  slowly  from  a  distillating  flask.  From  this  dis- 
tillate a  small  amount  of  water  will  separate.  The  xylol  standing 
above  the  water  is  poured  off  into  a  glass-stoppered  bottle,  with 


272  TECHNICAL  METHODS  OF  ANALYSIS 

a  tightly  fitting  stopper,  and  preserved  for  use  in  moisture  deter- 
minations. 

Connect  the  flask  containing  the  grease  and  xylol  with  a 
condenser,  which  must  be  perfectly  dry.  Heat  the  flask  gradually 
in  a  bath  of  cylinder  oil  and  distill  the  xylol  and  water  slowly 
until  the  xylol  comes  over  clear,  collecting  the  distillate  in  a 
funnel  tube  with  a  stem  graduated  to  0.1  cc.  The  bulk  of  the 
water  comes  over  with  the  first  10  cc.  of  distillate.  After  the 
distillation  is  completed,  wash  down  the  condenser  with  water- 
saturated  xylol  and  tap  the  funnel  tube  gently  until  any  small 
drops  of  water  clinging  to  the  sides  are  brought  down  to  the 
bottom.  Read  the  volume  of  water.  Each  0.1  cc.  is  equivalent 
to  1%  of  H2O  in  the  grease,  using  a  10-gram  sample. 

NOTE. — If  the  mixture  gives  trouble  from  frothing,  on  account  of  the  soap 
present,  add  sufficient  dry  fused  and  powdered  KHSO4  to  decompose  the  soap 
before  distilling. 

Free  Fatty  Acid. — Dissolve  or  disintegrate  5-10  grams  of  the 
grease  in  50  cc.  of  ethyl  alcohol  which  has  previously  been  neu- 
tralized with  phenolphthalein  and  0.1  N  KOH.  Digest  on  the 
water  bath  until  the  alcohol  beings  to  boil.  Titrate  with  0.1  N 
KOH  until  a  pink  color  persists  after  vigorous  shaking. 

CALCULATION.— 1  cc.  0.1  N  KOH  =  0.0282  gram  oleic  acid. 

Ash. — Ignite  2  grams  in  a  porcelain  crucible,  gently  at  first 
and  finally  at  a  higher  heat,  until  the  ash  is  as  nearly  white  as 
possible.  Cool  in  a  desiccator  and  weigh. 

Soap. — To  the  ash  add  a  few  cc.  of  water  and  a  drop  of  methyl 
orange  and  titrate  with  0.5  N  HC1.  Test  this  solution  quali- 
tatively for  Pb,  Ca,  K  and  Na  (see  also  page  280),  and  then  cal- 
culate the  titration  to  the  proper  soap  by  using  one  of  the  following 
factors : 

1  ce.  0.5  N  HC1  =  0.161  gram  K  stearate. 
=  0.153  gram  Na  stearate. 
=  0.152  gram  Ca  stearate. 

If  the  grease  is  made  up  of  a  Pb  soap,  the  Pb  may  be  deter- 
mined by  decomposing  the  grease  by  boiling  with  a  mixture  of 
H2SO4  and  HNOs,  evaporating  to  strong  fumes  of  SOs,  cooling, 
diluting  with  water  and  alcohol  and  weighing  as  PbSO^.  (See 
page  215).  In  the  case  of  a  pigmented  grease  determine  the  Pb 
in  the  ash.  (PbS04X2.55  =  Pb  Stearate.) 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        273 

If  a  rosin  soap  is  present,  the  figures  obtained  by  using  the 
above  factors  will  be  somewhat  low,  depending  upon  the  amount 
of  rosin  soap  present,  because  of  the  higher  combining  weight  of 
abietic  acid;  but  for  ordinary  purposes  they  will  be  sufficiently 
accurate. 

Mineral  Matter. — The  amount  of  ash  other  than  the  alkalies 
from  the  soap  may  be  determined  by  the  difference  between  the 
total  ash  and  the  alkali  found  by  titration.  In  this  case  the  alkali 
should  be  calculated  to  K2CO3,  Na2CO3  or  CaCOs,*  as  the  case 
may  be. 

In  the  case  of  greases  of  type  C,  shake  about  5  grams  of 
the  grease  with  2  separate  portions  of  ether  in  a  glass  cylinder  and 
then  centrifuge.  This  removes  free  oils  and  fats.  Decant  the 
ethereal  solution  through  a  filter  paper  which  has  previously  been 
weighed.  Wash  twice  with  ether  by  decantation.  Shake  the 
residue  with  alcohol  and  filter  through  the  same  filter  paper. 
Wash  with  alcohol.  This  removes  alcohol-soluble  soaps.  Dry 
the  paper  and  residue  at  100°  C.,  cool  in  a  desiccator  and  weigh. 
This  gives  the  total  amount  of  pigment,  f  If  graphite  is  present, 
ignite  the  residue  in  a  weighed  porcelain  crucible  and  subtract 
this  final  residue  from  the  total  pigment  for  the  amount  of  graphitic 
carbon.  In  general,  however,  this  last  step  is  unnecessary,  as  all 
that  is  desired  is  the  total  amount  of  graphite. 

The  above  determinations  are,  as  a  rule,  all  that  is  necessary 
in  an  examination  of  the  ordinary  types  of  grease.  It  may  be 
desirable,  however,  at  times  to  make  further  determinations  and 
these  are  given  below: 

Unsaponified  Oil  or  Fat. — The  unsaponified  oil  may  consist  of 
mineral  oil  together  with  unsaponified  saponifiable  oil  or  fat. 
This  may  be  determined  by  extracting  5-10  grams  of  the  grease 
with  neutral  ethyl  (sulfuric)  ether.  If  it  is  desired  to  know  its 
nature,  the  ether  extract  may  be  subjected  to  an  examination  for 
saponification  number,  iodine  number,  etc.  In  most  cases  where 
grease  contains  unsaponified  saponifiable  matter,  it  has  been 

*  The  lime.will  be  present  in  the  ash  as  CaCO3  rather  than  CaO  on  account 
of  the  large  amount  of  organic  matter,  unless  ignited  over  a  blast. 

t  This  figure  includes  any  alcohol-insoluble  soaps.  If  it  is  desired  to  correct 
for  these,  acidify  with  dil.  HC1  and  shake  out  with  ether.  Filter  the  ether 
solution  of  the  combined  fatty  matter,  wash  free  from  acid,  evaporate  off  the 
ether  and  weigh  the  fat.  Calculate  to  the  appropriate  soap. 


274  TECHNICAL  METHODS  OF  ANALYSIS 

made  by  a  partial  saponification  of  the  fat  in  question;  hence  the 
original  grease  may  be  saponified  directly  and  the  total  fatty  acids 
examined. 

Unsaponifiable  Mineral  Oil,  etc. — These  will  be  found  in  the 
ether  extract  of  the  grease,  together  with  the  unsaponified  saponi- 
fiable  matter  and  the  proportions  of  the  two  can  be  ascertained  by 
a  determination  of  the  saponification  number,  or  by  shaking  out 
with  ether  after  saponification  (see  page  261). 

Reporting  Results. — Under  ordinary  circumstances  report 
results  as  follows: 

1.  Type. 

2.  Melting  Point  (°  F.). 

3.  Moisture  (%). 

4.  Saponifiable  Oil  (%). 

5.  Mineral  Oil  (%). 

6.  Total  Mineral  Matter  (%). 

7.  Soap  (kind  and  %). 

8.  Pigment  (%  and  nature). 

Ordinarily  the  mineral  oil  is  taken  "  by  difference  "  after 
adding  together  items  3,  4,  7  and  8. 

DEGRAS  (WOOL  GREASE) 

The  term  "  Degras  "  in  its  present  commercial  sense  refers  to 
crude  wool  grease.  It  is  in  no  way  related  to  the  older  types,  of  a 
similar  name,  which  are  now  called  "  French  Degras  " — some- 
times "  Sod  Oil." 

Crude  wool  grease,  besides  the  grease  arising  from  sheep's 
wool,  contains  an  indefinite  amount  of  fatty  acids  recovered  from 
the  soap  used  in  washing  the  wool  and  obtained  in  the  same 
operation  to  which  the  wool  grease  is  subjected.  It  is  also  the 
custom  in  many  foreign  mills  to  treat  the  wash  waters,  arising 
from  the  scouring  of  cloth  or  yarn  with  soapy  water,  at  the  same 
time  that  the  wool  scourings  are  treated.  It  is  obvious  that 
the  grease  obtained  as  a  result  of  these  methods  will  in  all  cases 
contain  some  free  fatty  acid  from  soap ;  and  in  case  cloth  and  yarn 
waters  are  mixed  before  treatment,  there  will  also  be  a  certain 
further  amount  of  fatty  acid.  In  addition  there  may  be  a  neutral 
oil  or  even  a  mineral  oil  which  comes  from  the  cloth  or  yarn  scour- 
ing. It  is  apparent,  therefore,  that  no  standard  composition  can  be 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS         275 

ascribed  to  degras.  The  best  we  can  do  is  to  take  an  average  or 
approximate  composition. 

In  certain  types  of  standard  degras  where  the  oil  resulting  from 
cloth  washing  does  not  come  into  the  mixture,  repeated  extraction 
with  hot  95%  alcohol  and  pouring  off  the  hot  alcohol  solution  will 
finally  leave  a  residue  in  the  bottom  of  the  beaker  insoluble  in  hot 
alcohol.  This  we  have  found  to  be  about  25%  of  the  weight  of  the 
degras  taken.  In  other  cases  this  method  is  of  no  use. 

The  best  general  method  is  to  saponify  the  degras  with  excess 
of  alcoholic  KOH  in  a  pressure  bottle  for  at  least  eight  hours. 
After  evaporating  off  all  of  the  alcohol  and  taking  up  with  water, 
shake  out  the  unsaponifiable  matter*  with  ether,  evaporate  off  the 
ether  and  weigh  the  residue.  This  should  constitute  in  the 
neighborhood  of  35%  of  the  degras  taken  and  should  be  com- 
pletely soluble  in  hot  95%  alcohol,  the  latter  showing  absence  of 
mineral  oil. 

BEESWAX 

General. — The  common  adulterants  of  beeswax  are  rosin, 
paraffin,  ceresin,  stearic  acid,  spermaceti,  and  Japan  and  carnaiiba 
waxes;  while  to  a  less  extent  are  used  tallow,  starch,  sulfur,  and 
mineral  fillers.  Any  appreciable  amount  of  water  must  also  be 
looked  upon  as  an  adulterant. 

Preliminary  Tests. — As  a  preliminary  test  for  the  detection  of 
adulterants,  dissolve  a  portion  of  the  sample  in  cold  CHCls. 
Ceresin,  paraffin  wax,  carnaiiba  wax,  and  wool  wax  are  not  com- 
pletely soluble  and  any  considerable  quantity  may  thus  be 
detected  qualitatively,  as  well  as  starch  and  mineral  matter.  It 
should,  however,  be  borne  in  mind  that  bleached  white  beeswax  is 
not  readily  soluble  in  CHCla.  Pure  beeswax  should  also  be 
completely  souble  in  turpentine. 

Specific  Gravity. — Melt  the  wax  and  drop  it  by  means  of  a 
stirring  rod  upon  a  moist,  cold,  porcelain  surface  in  such  a  manner 
as  to  obtain  globules  of  about  |  inch  diameter.  Let  cool  for  at 
least  two  hours,  and  then  place  in  a  glass  cylinder  of  about  200  cc. 
capacity,  and  add  a  mixture  of  alcohol  and  water  of  sp.  gr.  about 
0.960  at  15°  C.  If  the  globules  sink  in  this  mixture,  add  water; 
if  they  rise,  add  alcohol.  Add  water  or  alcohol  with  rapid  agitation 
*  For  the  determination  of  unsaponifiable  matter,  see  page  261. 


276  'TECHNICAL  METHODS  OF  ANALYSIS 

until  the  globules  neither  rise  nor  sink  but  remain  suspended  in  the 
liquid  at  exactly  15.5°  C.  Then  take  the  sp.  gr.  of  the  liquid  at 
this  temperature  with  the  Westphal  balance.  This  gives  the  sp.  gr. 
of  the  beeswax  at  15.5°  C. 

Melting  Point. — Thinly  coat  the  bulb  of  an  accurate 'thermom- 
eter with  the  wax  and  let  stand  twenty-four  hours.  Place  the  bulb 
of  the  thermometer  in  a  large  test  tube,  holding  it  in  place  by  a  cork 
stopper  grooved  on  the  sides  so  as  to  allow  free  access  of  air. 
Immerse  the  test  tube  containing  the  thermometer  in  a  beaker  of 
water  and  raise  the  temperature  very  gradually  (1°  in  2-3  minutes). 
The  temperature  at  which  a  transparent  drop  forms  on  the  end 
of  the  thermometer  is  taken  as  the  melting  point. 

Iodine  Number. — Determine  the  iodine  number  by  the  Wijs 
method  as  described  on  page  241. 

Acid  Number. — Weigh  8  grams  into  a  500  cc.  Erlenmeyer  flask 
and  add  70  cc.  of  neutral  alcohol.  Heat  on  the  water  bath  until 
the  mixture  is  entirely  melted.  Then  add  1  cc.  of  phenolphthalein 
solution  and  titrate  the  mixture  quickly  with  0.5  N  alcoholic  KOH 
solution,  keeping  it  hot.  Calculate  the  number  of  milligrams  of 
KOH  required  to  neutralize  the  free  acid  in  1  gram  of  wax. 

CALCULATION.— 1  cc.  of  0.5  N  alkali  =  28.06  mg.  KOH. 

NOTE. — Instead  of  titrating  with  0.5  N  alcoholic  KOH,  the  determination 
may  be  made  with  0.5  N  or  0.1  N  aqueous  KOH.  In  this  case,  however,  it  is 
necessary  to  dilute  with  about  200  cc.  of  hot  neutral  alcohol  before  titrating 
and  to  keep  this  solution  hot  during  titration.  In  any  case  the  wax  must  be 
in  a  melted  state  during  titration. 

Saponification  Number. — Saponify  about  2  grams  of  wax 
(accurately  weighed)  for  at  least  three  hours  with  25  cc.  of  0.5  N 
alcoholic  KOH,  as  described  on  page  241.  Calculate  the  saponi- 
fication  number. 

Ester  Value  and  Ratio  Number. — Subtract  the  acid  number 
from  the  saponification  number.  The  difference  is  the  ester 
value.  Divide  this  by  the  acid  number.  The  quotient  is  the  ratio 
number.  For  pure  beeswax  the  ratio  number  lies  in  the  neighbor- 
hood of  3.8. 

NOTE. — If  the  saponification  number  of  the  sample  is  below  92  while  the 
ratio  number  is  normal,  then  paraffin  or  ceresin  must  be  present.  If  the  ratio 
number  exceeds  3.8,  then  adulteration  may  be  suspected  with  Japan  wax, 
tallow,  insect  wax,  carnaiiba  wax,  or  spermaceti.  If,  however,  the  acid  value 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        277 


is  much  below  20,  Japan  wax  is  absent.     If  the  ratio  number  is  less  than  3.8, 
stearic  acid  or  rosin  may  be  present. 

Moisture. — Determine  moisture  by  the  Xylol  Method  as 
described  on  page  271. 

Rosin. — Test  qualitatively  for  rosin  as  follows:  Heat  1  gram 
of  wax  for  a  few  minutes  with  1  cc.  of  50%  alcohol  (alcohol  of  this 
strength  will  not  extract  stearic  acid  if  present),  cool  and  filter. 
Evaporate  the  filtrate  to  dryness  on  the  water  bath  and  add  5  cc. 
of  acetic  anhydride.  Heat  to  boiling,  cool  thoroughly,  and  then 
carefully  let  1  drop  of  cone.  H2S04  flow  into  the  solution.  Rosin 
will  develop  a  fugitive  violet  color. 

Fatty  Adulterants. — Japan  wax  and  other  fatty  substances 
(such  as  tallow,  ceresin,  stearic  acid,  etc.)  may  be  detected  by 
boiling  1  gram  with  1.5  grams  of  borax  and  20  cc.  of  water,  where- 
upon the  aqueous  solution  will  become  milky  or  gelatinous  when 
cooled.  With  pure  beeswax  it  remains  clear  or  becomes  but  slightly 
turbid.  Carnatiba  wax  and  rosin  behave  similarly  to  pure  bees- 
wax. 

NOTE. — The  above  determinations  are  generally  sufficient  to  determine 
whether  a  sample  is  adulterated  or  not.  It  must  be  borne  in  mind,  however, 
that  beeswaxes  from  different  localities  vary  somewhat  in  composition,  also 
that  the  sp.  gr.  of  white  bleached  beeswax  is  somewhat  higher,  whereas  the 
other  "  constants  "  may  be  either  raised  or  lowered  according  to  the  method 
employed  in  bleaching.  Indian  beeswax  (Ghedda  wax)  is  softer  and  more 
plastic  than  normal  beeswax  from  European  and  domestic  sources.  It  has  a 
very  low  acid  value,  and  high  ester  value,  and  it  is  said  to  be  rarely  adul- 
terated. Care  must  be  taken  not  to  confuse  specimens  of  this  wax  (and  also 
Chinese  beeswax)  with  adulterated  beeswax. 

The  following  table  gives  the  approximate  figures  which  an 
unadulterated  sample  should  show: 


Ordinary  Beeswax 

Indian  Beeswax 

Sp  gr  at  15.5°  C  

0.958-0.970 

0.958-0.970 

Melting  point                                  

62-67°  C. 

60-68°  C. 

Iodine  number 

8-11 

5-11 

Saponification  value   

90-104 

76-130 

Acid  number                                   

17-21 

4.5-10 

Ester  value 

73-87 

69-123 

Ra/tio  number 

3  6-3  8 

7  4-17  9 

278  TECHNICAL  METHODS  OF  ANALYSIS 

In  an  adulterated  sample  the  following  tests  will  be  found 
useful : 

Stearic  Acid. — Boil  3  grams  of  wax  for  several  minutes  with 
10  cc.  of  80%  alcohol  and  let  cool  to  18-20°  C.  to  form  a  thick 
paste.  After  standing  one  hour,  filter  into  a  200  cc.  cylinder  and 
dilute  the  filtrate  with  water  to  about  200  cc.  If  stearic  acid  is 
present,  it  separates  into  flakes  and  collects  on  the  surface.  The 
test  is  sensitive  to  1%.  If  from  7-8%  are  present,  a  thick 
creamy  mixture  results.  Pure  beeswax  should  show  no  appreciable 
deposit  after  standing  one  to  two  hours. 

Paraffin. — Melt  2-10  grams  of  wax  in  a  porcelain  dish,  then  add 
an  equal  weight  of  finely  powdered  KOH.  Continue  heating  for  a 
few  minutes  with  continued  stirring.  Cool  and  powder  the  hard 
mass  and  mix  the  resulting  powder  with  3  times  as  much  potash 
lime  (1  part  KOH:  2  parts  CaO)  as  wax  used.  Then  introduce 
this  mixture  into  a  thick  walled  tube,  immerse  in  an  oil  bath  and 
heat  to  about  250°  C.  for  three  to  four  hours.  After  cooling,  finely 
powder  the  tube  with  its  contents,  place  the  mass  in  a  Soxhlet 
apparatus  and  extract  with  86°  naphtha  for  several  hours.  Evap- 
orate off  the  naphtha,  dry  the  residue  at  100°  C.  and  weigh. 
(Make  sure  the  naphtha  itself  leaves  no  residue  at  100°  C.)  By 
this  treatment  esters  are  converted  into  alcohols  and  these  alcohols 
on  heating  with  potash  lime  are  in  turn  converted  into  the  respect- 
ive acids,  while  hydrocarbons  present  are  not  affected  and  will 
extract  with  the  naphtha.  Pure  beeswax  contains  naturally  from 
12.5-14%  of  hydrocarbons  and  any  adulteration  with  paraffin 
or  allied  bodies  will  increase  this  percentage. 

NOTE. — For  further  information  in  regard  to  analysis  of  doubtful  samples, 
see  Allen  and  Lewkowitsch. 

REFERENCE. — Lewkowitsch:  "  Chemical  Technology  and  Analysis  of  Oils, 
Fats  and  Waxes,"  Volume  II,  page  751.  Allen:  "Commercial  Organic 
Analysis,"  Edition  IV,  Vol.  II,  pages  242-270.  U.  S.  Dept.  of  Agriculture, 
Bureau  of  Chemistry,  Bulletin  150,  page  49. 

PARAFFIN  WAX 

General. — For  ordinary  white  paraffin  wax  the  only  necessary 
determination  is  the  melting  point.  Yellow  waxes  and  paraffin 
scale,  however,  often  contain  a  considerable  amount  of  oil. 

Melting  Point.— (A)  CAPILLARY  TUBE  METHOD.— Take  a 
piece  of  capillary  tubing  about  1  inch  long,  soften  the  wax  in  the 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS        279 

fingers  if  necessary  and  push  one  end  of  the  tube  into  it,  filling  the 
tube  about  0.25  inch  from  the  end.  Fasten  the  tube  to  a  ther- 
mometer with  a  rubber  band  so  that  the  wax  is  opposite  the  bulb. 
Immerse  the  thermometer  bulb  and  tube  in  a  beaker  of  water  (it 
will  save  time  if  the  water  is  previously  warmed  to  about  90°  F.). 
Heat  slowly  with  a  low  flame  without  stirring  and  note  the  tem- 
perature at  which  the  wax  melts  and  runs  out  of  the  tube. 

(B)  "  ENGLISH  TEST." — The  English  Test  gives  in  reality  the 
solidifying  point.     Stir  the  melted  wax  in  a  small  cup,  about  2.5 
inches  in  diameter  by  about  2  inches  deep,  until  the  latent  heat 
given  up  by  the  crystallization  of  the  wax  arrests  the  fall  of  the 
mercury  column  momentarily.     Take  this  reading  as  the  melting 
point. 

(C)  "  AMERICAN  TEST." — This  gives  results  about  3°  F.  higher 
than  the  English  Test  and  is  determined  as  follows: 

A  hemispherical  cup,  3.75  inches  in  diameter,  is  three-fourthfi 
filled  with  melted  wax,  which  is  allowed  to  cool  without  stirring 
until  a  thin  film  forms  on  the  top  and  extends  from  the  sides  to  a 
thermometer  with  a  round  bulb,  0.5  inch  in  diameter,  suspended 
so  that  it  is  three-fourths  immersed  in  the  center  of  the  cup. 

NOTE. — As  the  American  Test  is  slow,  it  is  customary  to  take  the  Eng 
lish  Test  and  add  3°  F.  for  the  American.  Results  should  be  reported  in  terms 
of  Fahrenheit  degrees. 

Oil. — Chill  the  wax  and  powder  as  finely  as  possible,  weigh 
out  about  1  gram  and  digest  for  1-2  hours  in  10  cc.  of  acetone  at 
ordinary  temperature.  Mix  well,  then  place  in  a  freezing  bath 
and  cool  to  — 15°  C.  (5°  F.)  or  lower.  Filter  through  cotton  wool 
in  a  funnel  surrounded  by  a  freezing  mixture  and  wash  with  acetone 
which  has  been  chilled.  Evaporate  the  filtrate,  dry  at  not  over 
100°  C.  and  weigh  the  oil. 

REFERENCES.— J.  Soc.  Chem.  Ind.  25,  page  139  (1906);  Rogers- Aubert : 
"Industrial  Chemistry,"  1912  edition,  page  527. 

SOAP 

Sampling. — The  preparation  of  the  sample  requires  consider- 
able care,  since  the  moisture  content  of  the  outer  layer  may  be 
very  different  from  that  of  the  interior  of  the  cake. 


280  TECHNICAL  METHODS  OF   ANALYSIS 

If  the  sample  is  comparatively  dry,  it  is  a  good  plan  to  run  it 
through  a  meat  chopper  and  reduce  to  fine  particles,  repeating 
the  operation  several  times  in  order  to  obtain  a  homogeneous  sam- 
ple. If  the  soap  is  too  soft  to  permit  this  procedure,  the  cake 
should  be  cut  in  two  diagonally,  and  thin  shavings  taken  from  fresh 
surfaces,  care  being  taken  to  cut  entirely  across  in  order  to  obtain 
a  fair  proportion  of  the  outer  and  inner  parts.  The  sample  in 
either  case  should  be  thoroughly  mixed  and  kept  in  a  tightly 
stoppered  bottle. 

Moisture. — Weigh  out  20  grams  of  sample  and  dissolve  in 
about  150  cc.  of  hot  water.  Transfer  the  solution  while  still  hot 
to  a  250  cc.  graduated  flask  and  dilute  to  the  mark.  Mix  thor- 
oughly, pipette  25  cc.  while  hot  into  a  weighed  platinum  dish  and 
evaporate  to  dryness  on  the  steam  bath.  Then  dry  to  constant 
weight  at  110°  C.  The  percentage  of  solid  matter  subtracted 
from  100  gives  the  per  cent  of  moisture  and  volatile  matter. 

NOTE. — The  moisture  as  determined  above  may  also  include  alcohol  and 
essential  oils  if  they  are  present  in  the  soap,  also  naphtha  or  other  volatile 
substances.  In  such  cases  the  true  moisture  may  be  determined  by  the  Xylol 
method  (page  271),  using  about  20  grams  of  soap  and  acidifying  with  an 
excess  of  powdered  anhydrous  KHSO4  before  distilling. 

Total  Alkali. — Ignite  the  residue  from  the  moisture  determina- 
tion at  a  low  red  heat  until  all  carbonaceous  matter  is  burned  off. 
Weigh  the  mineral  residue,  which  consists  of  Na2COs  or  K^COs 
(also  SiO2,  NaCl,  etc.,  if  present).  Pour  boiling  water  into  the 
dish  and  warm  until  the  residue  is  dissolved.  Cool,  and  titrate 
with  0.1  N  acid  and  methyl  orange.  If  the  residue  is  not  com- 
pletely soluble  in  water,  the  insoluble  matter  should  be  filtered  off 
and  the  filtrate  evaporated  to  dryness,  ignited  and  weighed  before 
titration. 

The  alkali  by  titration,  calculated  to  either  Na2COs  or  K^COs, 
should  check  with  the  weight  of  soluble  ash  as  above  determined. 
If  it  does  not,  the  presence  of  both  Na  and  K  is  indicated  (pro- 
vided NaCl,  etc.,  are  absent).  To  confirm  the  presence  of  both 
elements,  take  an  amount  of  ash  the  size  of  a  pinhead,  dissolve  in  a 
few  drops  of  HC1,  put  one  drop  on  a  microscope  slide,  evaporate 
to  dryness  over  a  micro  burner  and  draw  across  it  with  glass  rod  a 
drop  of  saturated  uranium  acetate  solution  made  slightly  acid 
with  acetic  acid.  If  Na  is  present,  clear  cut  light  yellow  tetra- 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS         281 

hedra  of  sodium  uranium  acetate  will  appear.  Put  another 
small  drop  on  a  slide  and  run  in  from  the  side  a  smaller  drop  of 
H2PtCle.  Potassium  will  give  yellow  octahedra. 

CALCULATIONS.— 1  cc.  0.1  N  acid  =  0.005300  gram  Na2CO3. 

=  0.006910  gram  K2CO3. 
=  0.003100  gram  Na20. 
=  0.004710  gram  K20. 
Na2CO3  X  0.5848  =  Na2O. 
K2CO3  X  0.6816  =  K20. 

Total  Fatty  Matter. — Pipette  200  cc.  of  the  original  hot  soap 
solution  (see  Moisture)  into  a  beaker,*  add  dil.  HN03  until  slightly 
acid,  heat  on  the  water  bath  until  the  fatty  acids  have  collected 
in  a  clear  layer  on  top  and  the  solution  below  is  perfectly  clear. 
Cool  in  ice  water  or  let  stand  overnight.  Remove  the  layer  of 
fatty  acids  to  a  beaker.  Shake  out  the  clear  liquid  in  a  separatory 
funnel  with  2  portions  of  50  cc.  each  of  CHCls  to  remove  the  rest 
of  the  fatty  matter.  Transfer  the  CHCls  extract  to  the  beaker 
containing  the  fatty  cake  and  dissolve  the  latter.  Transfer  the 
solution  to  a  separatory  funnel,  rinsing  the  beaker  with 
.  Wash  the  CHCls  extract  -with  2  portions  of  20  cc.  of 
water.  Evaporate  off  the  CHCk,  dry  at  100°  C.  to  constant 
weight  and  weigh  as  total  fatty  matter. 

NOTES. — (1)  Fatty  acids  are  determined  above  as  acids,  whereas  they  exist 
in  the  soap  as  anhydrides,  which  for  ordinary  soap  materials  =  acids  X 0.9673 
(Lewkowitsch:  "Chemical  Technology  and  Analysis  of  Oils,  Fats  and 
Waxes,"  1895  edition,  page  624).  Usually  analyses  are  reported  giving  the 
total  fatty  matter  as  fatty  acids,  since  small  losses  are  almost  inevitable  in 
this  determination  and  for  commercial  analyses  the  direct  figure  obtained  is 
usually  the  most  satisfactory. 

(2)  Total  fatty  matter  as  determined  above  may  include  fatty  acids,  uncom- 
bined  fat,  rosin  and  hydrocarbons.     If  it  is  desired  to  determine  only  the  com- 
bined acids,  the  determination  should  be  made  on  a  portion  of  the  dry  soap 
previously  extracted   with  ether  or  86°  Baume*  gasoline,  as  described  later 
under  "  Unsaponified  Matter." 

(3)  If  fatty  acids  are  liquid  at  ordinary  temperature,  a  known  weight  of 
beeswax  or  stearic  acid  may  be  added  to  the  hot  liquid  before  chilling  to  form 
a  solid  cake.     The  weight  of  wax  added  should  be  about  equal  to  that  of  soap 
employed  and  should  be  deducted  of  course  from  the  weight  of  the  cake. 

*  Time  may  be  saved,  if  necessary,  by  pipetting  directly  into  the  separatory 
funnel;  then  acidify  and  shake  thoroughly  before  adding  CHC13. 


282  TECHNICAL  METHODS  OF  ANALYSIS 

Excess  of  H2O  may  be  removed  by  pressing  between  filters  and  the  cake  dried 
in  a  desiccator  (or  in  vacua)  and  weighed. 

(4)  If  further  examination  of  the  fatty  acids  is  to  be  made,  it  is  best  to  effect 
decomposition  of  the  soap  solution  in  a  separatory  funnel,  running  off  the 
aqueous  liquid  through  a  wet  filter  and  subsequently  allowing  the  fatty  acids 
to  run  on  the  filter,  where  they  are  washed  with  boiling  water. 

(5)  Cocoanut  and  palmnut  oil  soaps  yield  a  fatty  acid  soluble  to  a  slight 
extent  in  hot  water.     In  such  cases  the  separation  of  fatty  acids  should  be 
made  in  as  concentrated  a  solution  as  possible,  saturated  with  common  salt. 
The  washing  of  the  fatty  acids  should  be  limited  and  drying  carried  on  with  as 
little  exposure  to  heat  as  possible. 

(6)  If  it  is  necessary  to  determine    soluble  fatty  acids,    consult  Allen: 
"  Commercial  Organic  Analysis,"  fourth  edition,  Vol.  II,  page  432. 

Free  Caustic  Alkali  or  Free  Fatty  Acids. — Dissolve  5  grams  of 
soap  in  warm  neutral  95%  alcohol.  Filter,  using  a  hot  water 
funnel;  wash  with  hot  alcohol;  titrate  the  nitrate  with  0.1  N 
acid  and  phenolphthalein  and  calculate  to  NaOH  or  KOH;  as  the 
case  may  be. 

If  the  filtrate  is  acid,  titrate  with  0.1  N  caustic  and  calculate 
to  oleic  acid. 

CALCULATION.— 1  cc.  0.1  N  acid    =0.00400  gram  NaOH. 

Ice.  0.1  N  acid    =0.00561  gram  KOH. 
.     1  cc.  0.1  N  alkali  =  0.0282  gram  oleic  acid. 

NOTES. — (1)  The  presence  of  free  caustic  alkali  may  be  detected  by  treat- 
ing a  freshly  cut  surface  of  the  soap  with  a  few  drops  of  phenolphthalein 
solution.  If  no  red  coloration  appears,  it  may  be  assumed  that  free  caustic 
alkali  is  absent.  Either  free  caustic  or  sodium  silicate  will  give  a  bright  red 
coloration.  In  the  presence  of  excess  moisture,  however,  NasCO3  will  also 
give  this  color. 

(2)  If  the  soap  contains  both  free  alkali  and  free  fat,  the  above  method  is 
open  to  objection,  since  during  heating  with  alcohol  the  free  alkali  will  saponify 
some  of  the  free  fat. 

In  cases  where  great  accuracy  is  required,  Devine's  method  should  be 
used.  For  details  see  J.  Am.  Chem.  Soc.  22,  693  (1900). 

Free  Sodium  Carbonate. — Dissolve  the  residue  from  the  alco- 
holic solution  in  the  above  determination  by  pouring  boiling  water 
through  the  filter.  Wash,  cool  the  solution  and  titrate  with  0.1  N 
acid  and  methyl  orange.  Calculate  to  Na2COs  or  K^COs,  as  the 
case  may  be.  (It  is  well  to  make  a  flame  test  with  a  platinum 
wire  before  dissolving  the  residue.) 

CALCULATION.— 1  cc.  0.1  N  acid  =  0.005300  gram  Na2CO3. 


ANALYSIS  OF  OILS,  FATS,   WAXES  AND  SOAPS         283 

NOTE.  —  If  borax  or  sodium  silicate  is  present,  it  is  sufficiently  accurate 
for  commercial  purposes  to  assume  that  they  will  remain  insoluble  in  alcohol 
and  be  titrated  with  the  free  carbonate.  In  this  case  corrections  should  be 
made  on  the  methyl  orange  titration  of  carbonate  as  follows  : 

1  cc.  0.1  N  acid  =  0.013    gram  Na2Si4O9.* 

=  0.0191  gram  Na2B4O7-10H2O. 

Combined  Alkali  (Na2O  or  K2O).  —  Calculate  the  free  caustic 
and  free  carbonate  to  Na2O  or  K2O.   Deduct  from  the  total  alkali, 
calculated  to  Na20  or  K20,  and  the  difference  will  be  combined 
alkali  (provided  sodium  silicate  and  borax  are  absent). 
CALCULATION.—  NaOH    X  0.7748  =  Na20. 
KOH      X  0.8394  =  K2O. 
Na2C03X  0.5848  =  Na2O. 
K2CO3    X  0.6816  =  K2O. 

Sodium  Silicate.  —  The  presence  of  sodium  silicate  is  generally 
indicated  by  the  fact  that  the  weight  of  ash  is  greater  than  the 
weight  calculated  from  titration,  provided  of  course  that  insoluble 
abrasives  are  not  present.  The  amount  of  sodium  silicate  may  be 
ascertained  by  determining  Si02  in  the  soluble  ash  after  titration 
for  total  alkali.  Add  a  slight  excess  of  HC1,  evaporale  to  dryness, 
and  finally  bake  for  one  hour  at  130°  C.  Take  up  with  cone. 
HC1,  dilute  with  hot  water,  filter,  wash,  ignite  very  strongly  and 
weigh  as  SiO2.  From  this  weight  calculate  to  Na2Su09. 

CALCULATION.—  SiO2  X  1.257 


NOTE.  —  If  the  soap  contains  insoluble  matter,  make  a  water  solution, 
filter,  evaporate  the  filtrate,  burn  off  the  organic  matter  and  determine  SiO2 
as  above  directed. 

Borax.  —  Weigh  10  grams  of  soap  (or  5  grams  if  more  than  5% 
of  borax  is  suspected)  into  a  platinum  dish  and  add  2.15  grams 
of  fusion  mixture  (consisting  of  200  grams  Na2COs  and  15  grams  of 
Si02  finely  powdered).  To  this  mixture  add  15  cc.  of  alcohol,  mix 
with  the  aid  of  a  glass  rod  and,  after  washing  the  rod  with  a  little 
alcohol,  evaporate  the  mass  to  dryness  on  the  water  bath;  ignite 
until  combustible  material  is  destroyed,  cover  the  dish  with  a 

*  Theoretically  1  cc.  0.1  N  acid  =  0.01516  gram  Na2Si4O9  but  commercial 
silicate  varies  somewhat  in  composition  and  0.013  is  taken  as  being  nearer  the 
actual  average  titration. 


284  TECHNICAL  METHODS  OF  ANALYSIS 

piece  of  platinum  foil  and  fuse.  Completely  disintegrate  the 
fusion  by  boiling  with  water  and  transfer  the  solution  to  a  250  cc. 
round-bottom  flask.  Acidify  with  20  cc.  of  dil.  HC1  (1:1).  Heat 
nearly  to  boiling  and  add  a  moderate  excess  of  dry  precipitated 
CaCOs.  Connect  with  a  reflux  condenser  and  boil  vigorously. 
Filter  out  the  precipitate  through  a  folded  filter,  washing  several 
times  with  hot  water,  keeping  the  total  volume  of  liquid  below 
100  cc.  Return  the  filtrate  to  the  flask,  add  a  pinch  of  CaCOs 
and  again  boil  under  a  reflux  condenser.  Remove  the  flame  and 
connect  the  top  of  the  condenser  with  a  suction  pump.  Apply 
gentle  suction  until  the  boiling  has  nearly  ceased,  cool  to  ordinary 
temperature,  add  1  gram  of  mannite*  or  50  cc.  of  neutral  glycerol 
and  titrate  the  solution  with  0.1  N  NaOH  (free  from  carbonate) 
and  phenolphthalein.  After  the  end  point  is  reached,  add  1  gram 
more  of  mannite  or  10  cc.  more  of  neutral  glycerol  and  again 
titrate.  Repeat  this  process  until  the  addition  of  mannite  or  gly- 
cerol causes  no  further  action  on  the  end  point.  The  number  of 
cc.  of  0.1  N  NaOH  required,  multiplied  by  0.00955,  gives  the  equiv- 
alent of  borax  (Na2B4O7  •  10H2O)  present  in  the  solution. 

NOTES. — (1}  This  method  is  described  in  J.  Ind.  Eng.  Chem.,  5,  645 
(1913). 

(2)  It  is  always  advisable  to  test  the  soap  qualitatively  before  under- 
taking a  quantitative  determination. 

Qualitative  Test  for  Borax. — Place  about  1  gram  of  the  soap  in 
a  test-tube  with  10  cc.  of  dil.  HC1.  Heat  the  mixture  to  boiling, 
which  causes  the  fatty  acids  to  rise  to  the  surface.  Cool  under 
the  tap  and  filter  through  a  wet  filter  paper.  Immerse  a  strip  of 
turmeric  paper  in  the  mixture  and  dry  it.  If  borax  is  present,  the 
paper  will  acquire  a  deep  red  color  when  dry  and  this  color  will 
change  to  blue  or  green  when  treated  with  NHiOH  or  Na2COs 
solution.  The  test  is  sensitive  to  about  0.05%  of  borax  in  the 
soap. 

Insoluble  Matter. — Dissolve  5  grams  of  soap  in  75-100  cc.  of 
hot  water.  Filter  on  a  Gooch  crucible,  wash  with  hot  water,  dry 
at  105-110°  C.,  weigh  and  calculate  the  percentage  of  total  insol- 
uble matter.  Ignite  the  residue  and  calculate  the  percentage  of 
insoluble  mineral  matter. 

*  Mannite  gives  a  sharper  end-point  than  glycerol. 


ANALYSIS  OF  OILS,  FATS,   WAXES  AND  SOAPS         285 

Chlorides.— Evaporate  the  filtrate  from  the  fatty  acids  to 
about  100  cc.  Neutralize  carefully  with  CaCOs,  and  titrate  with 
0.1  N  AgN03,  using  K2Cr04  as  indicator.  (See  page  492.) 

CALCULATION.— 1  cc.  0.1  N  AgNOt  =  0.00585  gram  NaCl. 

=  0.00746  gram  KC1. 

Glycerol. — Dissolve  20-25  grams  of  soap  in  hot  water,  add  a 
slight  excess  of  H2SO4  and  heat  on  the  water  bath  until  fatty  acids 
separate  in  a  clear  layer.  Remove  the  fatty  acids  and  filter  the 
acid  solution  into  a  graduated  flask.  Remove  chlorides  and  sol- 
uble fatty  acids  by  adding  crystals  of  Ag2SO4.  Cool,  make  up  to 
the  mark,  mix,  let  settle  and  filter  through  a  dry  filter  paper. 
Place  an  aliquot  portion  corresponding  to  about  5  grams  of  soap 
in  a  100  cc.  graduated  flask,  dilute  slightly,  add  a  little 
silver  oxide,  let  stand  ten  minutes,  and  add  a  slight  excess 
of  basic  lead  acetate.  Make  up  to  the  mark,  filter  through 
a  dry  paper,  and  place  25  cc.  of  the  filtrate  in  a  perfectly 
clean  beaker.  Add  first  12  drops  of  H2SO4  (1:4)  to  precipitate 
the  Pb,  and  then  an  accurately  measured  amount  (40-50  cc.) 
of  a  solution  of  bichromate  (made  by  dissolving  74.56  grams 
of  pure  K2Cr2O?  in  water  and  diluting  to  1000  cc.),  and  then 
15  cc.  of  cone.  H2S04.  Cover  the  beaker  and  heat  for  two  hours 
in  boiling  water;  then  cool.  Add  an  excess  of  standard  ferrous 
ammonium  sulfate  solution  and  tirate  back  with  standard  bichro- 
mate solution  containing  7.456  grams  per  liter.  (The  ferrous 
ammonium  sulfate  solution  should  contain  about  240  grams  per 
1000  cc.)  1  cc.  of  the  stronger  bichromate  solution  corresponds 
to  0.01  gram  of  glycerol. 

In  the  presence  of  sugar  the  above  method  is  not  reliable, 
since  sugar  will  also  reduce  bichromate.  Consequently,  when 
sugar  is  present,  remove  the  fatty  acids  as  before,  neutralize  an 
aliquot  with  milk  of  lime,  evaporate  to  about  10  cc.,  add  2  grams  of 
sand  and  milk  of  lime  containing  about  2  grams  of  Ca(OH)2,  and 
evaporate  almost  to  dryness.  Treat  the  moist  residue  with  5  cc. 
of  96%  alcohol,  rub  the  whole  mass  into  a  paste,  heat  the  mixture 
on  the  water  bath,  stirring  constantly,  and  decant  the  liquid  into 
a  250  cc.  flask.  Wash  the  residue  5  or  6  times  with  small  portions 
of  alcohol,  cool  the  contents  of  the  flask  to  15°  C.,  fill  to  the 
mark  with  96%  alcohol,  mix,  and  filter  through  a  dry  paper. 


286  TECHNICAL   METHODS  OF  ANALYSIS 

Evaporate  200  cc.  of  the  filtrate  to  a  syrupy  consistency  on  the 
water  bath,  transfer  to  a  stoppered  cylinder  with  20  cc.  of  absolute 
alcohol,  add  3  portions  of  10  cc.  each  of  absolute  ether,  mixing 
after  each  addition ;  let  stand  until  clear,  pour  off  through  a  filter, 
and  wash  the  contents  of  the  cylinder  on  the  filter  with  a  mixture 
of  2  parts  of  absolute  alcohol  and  3  parts  of  absolute  ether.  Evap- 
orate to  a  syrup;  dry  for  one  hour  at  the  temperature  of  boiling 
water,  weigh,  ignite,  and  weigh  again.  The  loss  multiplied  by 
1.25  is  the  weight  of  glycerol  in  the  aliquot  taken.  (Instead  of 
weighing  the  glycerol  it  may  be  titrated  with  bichromate  after 
driving  off  the  alcohol  and  ether.) 

Sugar. — Dissolve  5  grams  of  soap  in  water,  add  an  excess  of 
HC1,  and  heat  on  the  steam  bath  for  thirty  minutes.  Cool  and 
filter  out  the  fatty  acids,  collecting  the  filtrate  in  a  volumetric 
flask.  Nearly  neutralize  the  excess  of  acid  with  NaOH,  make  up 
to  volume  and  mix.  For  analysis  take  an  aliquot  depending  upon 
the  amount  of  sugar  supposed  to  be  present.  The  aliquot  must 
not  contain  more  than  0.25  gram  of  sugar  calculated  as  dextrose. 
Determine  the  total  reducing  sugars  by  Allihn's  modification  of 
Fehling's  method  (see  page  407)  and  calculate  as  dextrose. 

Cane  sugar  =  Dextrose  X  0.95. 

NOTE. — Sugar  is  often  found  in  transparent  toilet  soaps,  especially  those 
sold  as  "  glycerin  soaps,"  to  the  extent  of  20-30%.  Such  soaps  also  often 
contain  alcohol  and  sodium  acetate. 

Unsaponified  Matter. — Dry  10  grams  of  soap  and  extract  in  a 
Soxhlet  extractor  with  ether  or  naphtha  (boiling  below  60°  C.). 
Transfer  the  extract  to  a  separatory  funnel  and  wash  twice  with 
water.  Evaporate  off  the  solvent,  dry  at  100-105°  C.  and  weigh. 

Naphtha. — For  the  determination  of  naphtha  or  other  hydro- 
carbons volatile  with  steam,  place  in  a  liter  round-bottom  wide- 
neck  flask  about  400  cc.  of  water  and  add  about  50  cc.  of  H2SO4 
(1:1).  After  cooling  the  solution,  if  necessary,  introduce  about 
100  grams  of  soap,  weighed  to  0. 1  gram,  into  the  flask.  The  soap 
should  be  weighed  as  one  piece  and  cut  quickly  into  as  large  pieces 
as  will  go  through  the  neck..  Then  introduce  into  the  neck 
of  the  flask  a  2-hole  rubber  stopper  connecting  through  one 
hole  by  a  bent  glass  tube  to  a  condenser.  Through  the  other  hole 
run  a  glass  tube  nearly  to  the  bottom  of  the  flask.  This  tube  is  for 
admission  of  steam.  Connect  the  outlet  of  the  condenser  by 


ANALYSIS  OF  OILS,   FATS,   WAXES  AND  SOAPS         287 

means  of  an  adapter  to  a  long  tube  graduated  to  0.1  cc.  A  gas 
burette  with  a  good-sized  bulb  at  the  bottom  is  satisfactory.  By 
means  of  a  rubber  tube  connected  to  bottom  of  this  burette 
water  can  be  drawn  off  as  it  accumulates  without  disturbing  the 
upper  layer  of  naphtha.  Surround  the  graduated  tube  with  ice 
water.  Heat  the  solution  in  the  flask  to  boiling  and  then  pass  in 
steam.  Continue  the  steam  distillation  until  the  condensate 
comes  over  perfectly  clear.  This  generally  requires  one  to  two 
hours.  Have  sufficient  water  in  the  measuring  tube  so  that  the 
upper  layer  of  naphtha  remains  in  the  graduated  portion,  carefully 
drawing  off  the  underlying  water  as  fast  as  necessary. 

After  completing  the  distillation,  let  the  contents  of  the  tube 
come  to  60°  F.  and  read  the  volume  of  the  upper  layer.  Then 
determine  the  sp.  gr.  at  60°  F.  of  the  volatile  distillate.  From  this 
calculate  its  weight.  Transfer  the  entire  volatile  distillate  to  an 
Erlenmeyer  flask.  Add  25  cc.  of  alcohol  which  has  been  neu- 
tralized to  phenolphthalein,  warm  on  the  steam  bath  about  fifteen 
minutes  and  titrate  with  0.1  N  NaOH  and  phenolphthalein.  This 
gives  the  fatty  acids  volatile  with  steam.  Calculate  the  total 
weight  of  fatty  acids  as  oleic  acid  and  subtract  from  the  weight 
of  the  volatile  distillate.  Figure  the  difference  to  percentage 
of  naphtha  by  weight. 

CALCULATION. — 1  cc.  0.1  N  NaOH  =  0.028  gram  oleic  acid. 

Heavy  Petroleum  or  Hydrocarbons  Non-volatile  with  Steam.— 
Dissolve  10-15  grams  of  soap  in  hot  water,  using  as  little  as  pos- 
sible, add  50  cc.  of  0.5  N  alcoholic  KOH  and  evaporate  to  dryness. 
Dissolve  in  water,  transfer  to  a  separatory  funnel  and  extract  with 
ether.  Wash  twice  with  water,  evaporate  off  the  solvent,  dry  at 
100-105°  C.  and  weigh. 

Rosin. — Dissolve  3  grams  of  the  dry  fatty  acids,  separated  as 
under  "  Total  Fatty  Matter,"  in  30  cc.  of  absolute  alcohol  in  a 
flask  and  pass  dry  HC1  gas  through  the  solution  in  a  moderate 
stream.  Keep  the  flask  cool  by  placing  in  a  vessel  of  cold  water. 
Continue  passing  the  gas  until  the  esters  separate  and  no  more 
gas  is  absorbed,  which  usually  requires  about  forty-five  minutes. 
Let  the  flask  stand,  stoppered,  about  one  hour  to  complete  the 
reaction.  Dilute  with  5  times  the  volume  of  water  and  boil  until 
the  acid  solution  is  clear  and  the  esters  containing  the  rosin  float  on 
top.  Transfer  to  a  separatory  funnel  and  wash  the  flask  out  with 


288  TECHNICAL  METHODS  OF  ANALYSIS 

50  cc.  of  naphtha  (74°  Be*.).  Run  off  the  acid  solution,  wash  the 
naphtha  solution  once  with  water,  treat  with  a  solution  of  0.5 
gram  of  KOH  and  5  cc.  of  alcohol  in  50  cc.  of  water  and  shake. 
The  rosin  is  immediately  saponified  and  the  2  layers  will  separate 
completely.  Draw  off  the  lower  solution  of  rosin  soap  into  another 
separatory  funnel,  acidify  with  dil.  HC1  and  shake  out  three  times 
with  ether.  Wash  the  combined  ether  extract  twice  with  water, 
draw  into  a  weighed  flask,  evaporate  off  the  ether,  dry  the  rosin 
at  100°  C.  and  weigh.  Calculate  the  percentage  in  the  total 
fatty  matter  and  in  the  original  soap. 

NOTE. — The  above  method  is  that  described  by  Twitchell,  J.  Soc. 
Chem.  Ind.  13,  804  (1891),  and  depends  upon  the  fact  that  aliphatic  acids  are 
converted  into  ethyl  esters  by  HC1  in  alcoholic  solution,  whereas  rosin  remains 
unchanged. 

Miscellaneous  Substances. — Metallic  substances  such  as  Pb, 
Hg,  Cu,  and  Zn  will  be  found  in  the  filtrate  from  the  Si02  deter- 
mination and  may  be  determined  by  the  usual  methods. 

Dextrin,  starch,  gelatin,  etc.,  are  sometimes  present  in  soap 
and  they  may  best  be  determined  in  aliquot  portions  of  the 
filtrate  from  the  total  fatty  matter.  In  this  case,  however, 
H2S04  or  HC1  should  be  used  in  place  of  HNOs  to  separate  the 
fat. 

Carbolic  acid  and  coal  tar  products  may  be  determined  by  the 
method  described  in  Allen's  "  Commercial  Organic  Analysis," 
4th  edition,  Vol.  II,  page  426. 


CHAPTER  VIII 

ANALYSIS  OF  WOOD,  PAPER  AND  PAPER-MAKING 
MATERIALS 

CELLULOSE  IN  WOOD 

Sampling. — Samples  are  best  obtained  from  green  wood.  If 
the  wood  is  dry  it  should  be  soaked  in  water.  Place  the  wood  in  a 
vise  and  rasp  across  the  grain  with  a  woodworker's  rasp,  the  idea 
being  to  obtain  the  sample  in  as  fibrous  a  condition  as  possible, 
like  mechanical  pulp.  Dry  the  rasped  wood  at  98-100°  C. 
Weigh  out  samples  of  5  grams  each  into  500  cc.  casseroles. 

Analytical  Procedure.— Add  200  cc.  of  1%  NaOH  solution 
to  the  fiber,  cover  with  a  watch  glass  and  boil  gently  for  one-half 
hour,  washing  the  fiber  down  from  the  sides  of  the  vessel  several 
times.  Filter  with  suction  on  a  1-inch  perforated  plate  placed  in  a 
5-inch  funnel.  A  little  of  the  fiber  will  run  through  the  plate  at 
first  and  must  be  poured  back  after  a  good  mat,  like  an  asbestos 
filter,  is  formed.  In  order  to  hold  the  plate  firmly  in  the  funnel 
during  filtration  and  the  subsequent  manipulations,  pass  a  piece 
of  fairly  stiff  silver  wire  up  through  one  of  the  holes  in  the  center 
of  the  plate  and  securely  fasten  it  by  bending  the  end  down.  Let 
the  silver  wire  extend  down  through  the  stem  of  the  funnel,  pro- 
jecting J  inch  beyond  the  end.  By  putting  one  or  two  slight 
bends  in  this  wire  it  can  be  made  to  bear  against  the  inside  walls 
of  the  stem,  holding  the  filter  plate  firmly  in  place. 

Wash  the  boiled  wood  with  a  good  volume  of  hot  water,  suck 
dry,  loosen  up  the  fiber  with  a  sharp-pointed  glass  rod,  and  attach 
the  stem  of  the  funnel  to  the  rubber  tube  leading  from  a  chlorine 
generator  (under  the  hood) .  Cover  the  funnel  with  a  watch  glass 
and  pass  a  stream  (between  1  and  2  bubbles  per  second)  of  washed 
chlorine  gas  up  through  the  fiber.  Continue  the  chlorination  for 
one  hour.  Every  fifteen  minutes  the  fiber  should  be  loosened  and 
the  lumps  broken  up  with  the  pointed  rod. 

289 


290  TECHNICAL  METHODS  OF  ANALYSIS 

After  chlorination  return  the  funnel  to  the  suction  flask  and 
wash  with  hot  water  to  remove  HC1.  Place  150  cc.  of  2%  Na2SO3 
in  a  wash  bottle.  Invert  the  funnel  over  a  500  cc.  casserole,  push 
on  the  silver  wire  until  the  main  mass  of  the  fiber  with  the  filter 
plate  drops  into  the  casserole,  turn  the  funnel  right  side  up  and 
wash  out  all  the  fiber  with  a  stream  of  Na2SOs  solution  from 
the  wash  bottle.  Wash  the  wire  and  plate  and  add  the  remaining 
Na2SOs.  Bring  the  mixture  to  a  boil,  add  3  cc.  of  10% 
NaOH  and  boil  for  five  minutes.  Again  collect  the  fiber  on  the 
filter  plate,  wash  with  hot  water  until  the  washings  are  colorless, 
loosen  up  and  expose  to  chlorine  as  before. 

With  the  wood  of  some  broad-leaved  species  all  of  the  lignin 
is  removed  by  the  first  chlorination  and,  instead  of  coloring  yellow 
the  second  time  in  chlorine  gas,  the  fiber  bleaches  to  a  pure  white. 
With  most  coniferous  woods  the  fiber  turns  yellow  when  exposed 
to  chlorine  the  second  time.  In  that  event  chlorination  is  con- 
tinued for  one-half  hour,  the  fiber  washed  and  boiled  in  alkaline 
Na2SOs  solution  as  before,  and  again  exposed  to  chlorine.  Except 
in  very  unusual  cases  the  fiber  will  bleach  when  exposed  to  chlorine 
the  third  time.  At  whatever  stage  the  fiber  bleaches  white, 
remove  it  immediately  from  the  generator,  wash  on  the  filter 
plate  with  a  large  amount  of  water,  transfer  with  the  aid  of  dis- 
tilled water  to  a  casserole,  let  stand  under  water  for  a  short  time, 
collect  in  a  large  sized  tared  Gooch  crucible,  and  wash  well  with 
alcohol  and  finally  with  ether. 

Dry  the  product,  at  first  at  a  gentle  heat,  and  weigh  it. 

NOTES. — (1)  It  is  almost  impossible  to  wash  out  the  last  traces  of  acid, 
and  unless  the  fiber  is  washed  with  alcohol  and  ether,  the  slow  drying  with 
the  concentration  of  acid  at  the  drying  surfaces  will  cause  a  browning  of  the 
edge  of  the  cellulose. 

(2)  If  for  any  reason  there  should  be  any  mineral  matter  present  which 
would  not  be  removed  by  the  treatment,  ignite  the  dried  product  and  sub- 
tract the  weight  of  the  ash,  to  obtain  the  pure  cellulose. 

(3)  This  method  was  prepared  by  Arthur  D.  Dean  in  1906,  and  has  given 
good  results  in  this  laboratory. 

WOOD  PULP  SAMPLING  AND  TESTING 

General. — The  following  procedures  for  sampling  and  testing 
wood  pulp  have  been  used  in  this  laboratory  for  many  years.  The 
method  for  sampling  machine-dried  pulp  in  bales  was  originally 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS        291 

developed  in  this  laboratory  and  has  been  adopted  as  the  official 
method  of  the  American  Pulp  and  Paper  Association  and  the  Asso- 
ciation of  American  Wood  Pulp  Importers.  A  resume  of  the 
requirements  of  the  above  associations  is  given  at  the  end  of  this 
method.  At  the  present  writing  no  method  for  sampling  wood 
pulp  in  laps  has  been  officially  adopted  for  general  use  in  this 
country,  but  the  strip  method  as  here  described  is  extensively 
used. 

SAMPLING 

Pulp  in  Bales  (Machine  Dried). — The  sample  shall  be  taken  by 
boring  into  a  bale  to  a  depth  of  3  inches  with  a  special  augur 
bit  *  or  with  a  machine  cutter  using  a  single  knife.  The  discs, 
which  are  approximately  4  inches  in  diameter,  shall  be  removed 
and  ten  of  them  taken  as  a  sample,  selected  as  follows:  One  disc 
shall  be  taken  from  the  second  sheet  of  the  wrapper,  2  discs  from  a 
depth  of  1  inch,  3  discs  from  a  depth  of  2  inches,  and  4  discs 
from  a  depth  of  3  inches.  At  least  5%  of  all  the  bales  in  a  lot 
shall  be  sampled,  although  in  any  case  10  shall  be  the  minimum 
number  of  bales  sampled. 

The  holes  to  be  bored  shall  be  so  located  that  in  5  successive 
bales  they  will  represent  a  portion  extending  diagonally  across  the 
bale;  the  first  hole  to  be  bored  at  the  corner,  the  edges  of  the  cut 
being  at  a  distance  of  1  inch  from  the  edge  of  the  bale;  the  second 
cut  shall  then  be  made  half  way  between  the  location  of  the  first 
and  the  center,  the  third  at  the  center,  and  so  on  until  the  fifth 
bale  is  sampled  in  the  opposite  corner  in  a  position  corresponding 
to  the  first. 

Pulp  in  Rolls. — The  sample  shall  be  taken  in  the  same  manner 
as  for  pulp  in  bales.  The  position  of  the  samples  taken  shall  be 
determined  according  to  the  following  plan: 

The  first  sample  shall  be  taken  so  that  the  edge  of  the  disc 
shall  be  within  1  inch  of  the  end  of  the  roll,  the  second  half-way 
between  the  first  and  the  center,  the  third  at  the  center,  and  so  on. 

Pulp  in  Laps  (Wet  Pulp). — (A)  CUTTING  OF  SAMPLE. — The 
sample  shall  be  taken  by  cutting  a  strip  about  1  inch  f  wide  from 

*  These  may  be  obtained  from  the  Millers  Falls  Co.,  Millers  Falls,  Mass. 
t  A  narrower  or  wider  strip  may  be  adopted,  provided  the  same  width  is 
cut  from  every  bale  sampled. 


292  TECHNICAL  METHODS  OF  ANALYSIS 

the  center  of  the  folded  section  to  the  middle  of  the  outside  edge; 
the  cut  shall  be  made  in  each  case  half-way  through  the  lap. 
The  cuts  to  be  made  shall  be  so  located  that  in  four  successive 
laps  they  will  represent  a  cross  having  its  center  at  the  center  of 
the  top  face  of  the  lap  and  each  arm  terminating  in  the  center  of 
one  of  the  four  edges.  The  diagram  (Fig.  15)  will  show  the  posi- 
tion of  the  cuts.  The  fifth  lap  shall  be  sampled  the  same  as  the 
first,  and  so  on. 

(B)  SELECTION  OF  'THE  LAPS. — When  the  pulp  is  loose  in 
laps,  the  number  of  laps  to  be  sampled  shall  be  not  less  than  one 
in  every  2000  pounds  of  wet  pulp.  In  sampling  from  a  car,  care 
shall  be  taken  that  the  sample  laps  fully  represent  every  portion  of 


1st  Lap  2nd  Lap  3rd  Lap  4th  Lap 

FIG.  15. — Method  of  Sampling  Pulp  in  Laps. 

the  car.     With  loose  pulp  it  is  necessary  to  weigh  the  whole  car- 
load. 

When  the  laps  are  bundled  together  in  bales,  the  total  number 
of  bales  shall  be  ascertained  and  not  less  than  2.5%*  of  this  number 
shall  be  weighed  and  sampled.  Each  bale  sampled  shall  be 
opened  and  one  lap  withdrawn ;  the  samples  from  these  laps  shall 
be  cut  as  above  described  and  the  laps  shall  be  taken  from  the 
bales  as  follows: 

From  20%  of  the  bales  sampled,  withdraw  the  middle  lap. 

From  40%  of  the  bales  sampled,  withdraw  the  lap  half-way 
between  the  outside  and  the  center. 

From  35%  of  the  bales  sampled,  withdraw  the  lap  next  to 
the  outside. 

From  5%  of  the  bales  sampled,  withdraw  the  outside  lap. 

Those  laps  which  are  withdrawn  from  the  outside  of  the  bales 
shall  be  sampled  on  that  side  which  formed  the  surface  of  the 
bale. 

*  It  is  convenient  to  work  with  a  multiple  of  20. 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       293 


TESTING  OF  SAMPLES 

All  samples  immediately  upon  being  taken  shall  be  placed  in  a 
suitable  air-tight  container,  the  cover  of  which  shall  not  be 
removed  until  after  weighing.  The  samples  shall  then  be  dried 
in  a  suitable  oven  provided  with  good  ventilation,  at  a  temperature 
of  204-220°  F.  (95-105°  C.)  until  successive  weighings  made 
after  an  interval  of  not  less  than  three  hours  show  no  further  loss 
in  weight.  From  the  loss  thus  obtained,  the  total  percentage  of 
moisture  shall  be  calculated,  and  the  difference  between  this  and 
100%  will  represent  the  amount  of  bone-dry  pulp.  Air-dry  pulp 
is  understood  to  consist  of  90%  of  absolutely  dry  pulp  and  10% 
of  water.  The  percentage  of  air-dry  pulp  should,  therefore,  be 
calculated  by  dividing  the  bone-dry  percentage  by  0.90. 

NOTE. — The  scales  used  for  weighing  the  samples  must  be  accurate  to 
1  gram  or  less.  (If  avoirdupois  scales  are  used,  they  should  be  capable  of 
weighing  to  0.01  oz.) 

OFFICIAL  METHOD  OF  AMERICAN  PULP  AND  PAPER  ASSOCIATION 
AND   ASSOCIATION   OF  AMERICAN  WOOD   PULP   IMPORTERS 

General. — All  tests  must  be  made  by  a  chemist  duly  authorized 
and  approved  by  the  Joint  Committee  representing  the  Associa- 
tion of  American  Wood  Pulp  Importers  and  the  American  Pulp 
and  Paper  Association,  and  must  be  made  strictly  in  accordance 
with  the  following  instructions — otherwise  the  Committee  reserves 
the  right  to  withdraw  the  approval  of  any  chemist  at  any  time. 

Before  proceeding  to  the  weighing  and  sampling,  the  chemist 
must  ascertain  that  not  less  than  one-half  of  the  parcel  in  question 
is  available. 

Chemists  must  have  proper  and  adequate  equipment  for  weigh- 
ing and  sampling  the  bales  and  for  the  weighing  and  drying  of 
samples. 

All  sampling  of  pulp  must  be  done  by  or  supervised  by  the 
approved  chemist  personally,  or  by  his  competent  bona  fide 
assistants. 

Each  chemist  must  file  with  the  Committee  a  complete  list  of 
his  bona  fide  assistants,  who  will  do  the  sampling,  sucji  list  to  have 
the  approval  of  the  Committee.  The  chemist  will  be  held  respon- 
sible for  the  correct  sampling  by  his  approved  assistants. 


294  TECHNICAL  METHODS  OF  ANALYSIS 

The  Committee  shall  at  any  time  have  the  privilege  of  investi- 
gating the  sampling  done  by  chemists  or  their  assistants. 

Every  test  certificate  shall  clearly  state  the  name  of  the  person 
who  did  the  sampling. 

The  test  certificates  hereafter  shall  be  uniform  and  in  accord- 
ance with  forms  to  be  approved  by  the  Committee,  a  sample  draft 
of  which  will  be  furnished  by  the  Committee  to  each  chemist. 

Number  of  Bales  to  be  Sampled. — Not  less  than  5%,  nor  more 
than  10%,  of  the  entire  shipment,  but  not  less  than  10  bales,  shall 
be  sampled;  samples  to  be  drawn  only  from  sound  and  intact  bales, 
from  different  sections  of  the  entire  shipment,  and  the  analyst 
shall  be  careful  to  observe  that  no  unusual  conditions  prevail  in 
the  selection  of  the  bales.  The  accurate  weight  of  all  bales  sam- 
pled is  to  be  ascertained  by  a  sworn  weigher  before  sampling,  or, 
whenever  a  sworn  weigher  is  not  available,  by  a  competent  person, 
who  must  make  sworn  affidavit  that  the  weights  are  correct;  and 
no  other  bales  than  those  weighed  are  to  be  sampled,  and  whenever 
bales  are  numbered,  the  number  is  to  be  given  in  addition  to  the 
weight. 

Method  of  Sampling. — The  method  of  sampling  is  the  same  as 
previously  described  under  Pulp  in  Bales. 

Weighing  of  Samples. — All  samples  must  be  either  weighed 
by  accurate  scales  immediately  after  being  drawn  from  the  bales 
or,  where  this  is  impracticable,  must  be  put  into  air-tight  vessels, 
made  of  metal  or  glass  with  ground  glass  or  metal  stoppers,  and 
due  care  must  be  used  in  the  transportation  of  such  samples  until 
they  can  be  properly  weighed  at  the  laboratory  of  the  chemists 
The  entire  bulk  of  samples  selected  from  the  bales  must  be  dried 
out  for  the  test.  The  temperature  in  the  drying  oven  shall  be  as 
near  to  212°  F.  as  possible,  but  shall  not  exceed  220°  F.,  nor  be 
less  than  204°  F. 

SULFATE  COOK  LIQUOR 

General. — In  the  usual  sulfate  process  for  making  wood  pulp 
the  principal  ingredients  of  the  liquor  used  for  cooking  the  wood 
are  NaOH,  Na2S04,  JS^COs,  and  Na2S.  The  active  agents  in 
the  digestive  process  are  NaOH  and  Na2$,  and  it  is  stated  that 
these  combine  with  roughly  50%  of  the  weight  of  the  dried  wood 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       295 

to  form  soluble  organic  sodium  salts.  The  liquor  used  for  cooking 
wood  is  generally  referred  to  as  White  Liquor,  the  residual  liquor 
after  the  cooking  as  Black  Liquor. 

The  waste  sulfate  liquor  (Black  Liquor),  obtained  from  cooking 
pulp  materials  by  the  sulfate  process,  contains  in  addition  to  small 
amounts  of  silicate,  various  organic  salts  of  sodium  and  also  vary- 
ing proportions  of  Na2S,  Na2SO4,  Na2S03,  NaOH  and  Na2CO3. 

BLACK  LIQUOR 

Specific  Gravity. — Determine  the  sp.  gr.  at  15.5°  C.  with  the 
Westphal  balance  and  calculate  the  gravity  Baume. 

Total  Solids. — Weigh  out  100  grams  of  the  material  and  dilute 
to'  1  liter  with  distilled  water  in  a  graduated  flask.  Mix  thor- 
oughly and  pipette  into  a  weighed  platinum  dish  50  cc.  (equivalent 
to  5  grams).  Evaporate  on  the  steam  bath  and  then  dry  to  con- 
stant weight  at  105°  C.  There  will  be  some  loss  of  H2S  but  the 
result  will  be  approximately  correct. 

Ash. — Ignite  the  above  residue  until  the  carbon  is  burned  off. 
In  case  it  is  not  possible  to  burn  off  all  the  carbon,  dissolve  in 
water  and  filter  through  an  ashless  filter  into  a  beaker.  Ignite 
the  filter  paper  in  the  same  platinum  dish.  Cool  and  add  the 
filtrate  to  the  dish.  Evaporate  to  dryness,  ignite  gently,  cool  in 
a  desiccator  and  weigh. 

Silica. — Moisten  the  ash  above  obtained  with  cone.  HC1, 
warm,  add  a  few  cc.  of  water,  evaporate  to  dryness  on  the  steam 
bath,  bake  at  least  one  hour  at  120°  C.,  take  up  with  dil.  HC1, 
heat  to  boiling,  filter  through  a  quantitative  filter,  wash  with  hot 
water,  ignite  strongly  in  a  platinum  dish  and  weigh  as  SiO2. 
Save  the  filtrate. 

Sodium  Sulfate. — Pipette  25  cc.  of  the  original  sample  into  a 
beaker,  add  about  100  cc.  of  distilled  water,  make  slightly  acid 
with  HC1  and  heat  to  boiling.  Add  10  cc.  of  hot  BaCl2  solution 
slowly,  drop  by  drop,  boil  for  0.5  hour  and  filter,  washing,  with  hot 
water.  Ignite  in  a  weighed  platinum  crucible.  On  account  of  the 
organic  matter  present,  some  of  the  BaS04  is  likely  to  be  reduced 
to  BaS.  Moisten  the  precipitate  in  the  crucible  with  a  few  drops 
of  dil.  H2SO4.  Again  ignite,  cool  and  weigh  as  BaSO4.  Cal- 
culate to  Na2SO4  and  also  to  Na2O. 


296  TECHNICAL  METHODS  OF  ANALYSIS 

CALCULATION.— BaSO4  X  0.6086  =  Na2S04. 
BaS04X0.2656  =  Na20. 

Total  Sodium. — Take  an  aliquot  of  the  original  solution  corre- 
sponding to  5  grams  of  the  sample,  add  an  excess  of  HC1,  evaporate 
to  dryness  and  ignite  to  a  dull  red  heat.  All  the  sodium  salts  except 
the  sulfate  are  decomposed  to  NaCl.  The  temperature  must  be 
kept  low  to  avoid  volatilization  of  the  latter.  Leach  out  the 
residue  with  hot  water  and  filter.  Cool  and  titrate  the  NaCl 
with  0.1  N  AgNOs  solution  in  the  usual  way,  using  Na2Cr04  as 
an  indicator. 

It  is  necessary  to  leach  the  residue  thoroughly  with  small  por- 
tions of  hot  water  and  to  remove  all  the  particles  from  the  dish. 
For  accurate  work  it  is  desirable  to  filter  and  ignite  the  residue  on 
the  filter  gently  in  a  platinum  dish  and  again  leach  with  water. 
The  leaching  should  be  continued  until  the  filtrate  gives  no  reac- 
tion with  AgNOs.  Calculate  the  titration  to  Na20. 

CALCULATION.— 1  cc.  0.1  N  AgNO3  =  0.003 100  gram  Na2O. 

The  sum  of  the  Na20  thus  found  and  the  Na20  found  present 
as  sulfate  gives  the  total  sodium  as  Na2O. 

Sodium  Sulfide  (Volumetric  Zinc  Method). — SOLUTIONS. — (A) 
Standard  Zinc  Solution. — Dissolve  16.75  grams  of  c.  P.  30-mesh 
zinc  powder  in  a  small  excess  of  HNOs.  Add  sufficient  NH^OH 
to  redissolve  all  the  precipitate  formed  and  then  50  cc.  excess. 
Dilute  to  2000  cc.  (If  any  precipitate  forms  after  dilution,  insuf- 
ficient NELiOH  was  added.) 

(B)  Ammoniacal  Nickel  Sulfate  Indicator. — Make  an  approx- 
imately 10%  solution  of  nickel  ammonium  sulfate  and  add  a 
slight  excess  of  NILiOH. 

TITRATION. — From  the  solution  previously  prepared  for  Total 
Solids  pipette  out  100  cc.  (equivalent  to  10  g^ams  of  the 
original).  Dilute  to  about  250  cc.  in  a  beaker  with  distilled  water 
and  run  in  from  a  burette  the  standard  zinc  solution.  The  end 
point  is  reached  when  a  drop  of  the  solution  in  the  beaker  added 
to  three  drops  of  the  nickel  sulfate  indicator  tested  on  a  white 
spot  plate  no  longer  forms  a  black  precipitate.  From  the  number 
of  cc.  of  zinc  solution  required  calculate  the  amount  of  Na2S. 

CALCULATION. — 1  cc.  zinc  solution  =  0.0100  gram  Na2S. 

Total  Available  Alkalinity. — Evaporate  25  cc.  of  the  original 
sample  to  dryness  in  a  platinum  dish,  ash  over  a  Tirrill  burner 


WOOD,    PAPER  AND  PAPER-MAKING  MATERIALS       297 

and  leach  out  the  soluble  salts  with  hot  distilled  water  as  in  the 
determination  of  Total  Sodium  above.  Cool  the  filtrate  and  titrate 
with  0.5  N  acid  and  methyl  orange.  Calculate  the  titration 
to  Na2O  and  also  to  NaOH.  This  gives  the  alkalinity  available 
for  recovery. 

CALCULATION. — 1  cc.  0.5  N  acid  =  0.01550  gram  Na20. 

=  0.02001  gram  NaOH. 

Free  Caustic  Soda. — Pipette  100  cc.  of  the  Black  Liquor  (cal- 
culate the  weight  from  its  sp.  gr.)  into  a  500  cc.  volumetric  flask 
and  add  50  cc.  of  10%  BaCb  solution.  Shake  and  dilute  to  the 
mark  with  distilled  water,  freshly  boiled  and  free  from  CO2.  Let 
settle  clear.  Pipette  50  cc.  of  the  clear  supernatant  liquor  (equal 
to  10  cc.  of  the  original)  into  a  beaker  and  titrate  with  0.1  N  HC1 
and  phenolphthalein.  Calculate  to  NaOH. 

CALCULATION.— 1  cc.  0.1  N  acid  =  0.004001  gram  NaOH. 

NOTE. — The  above  determination  must  be  corrected  for  Na2S,  if  present, 
as  the  latter  reacts  to  phenolphthalein  when  it  is  half  neutralized,  according 
to  the  reaction:  Na2S+HCl  =  NaSH-f  NaCl.  Hence  1  cc.  0.1  N  HC1  = 
0.007806  gram  Na2S.  To  apply  the  correction,  therefore,  calculate  the  weight 
of  Na2S  which  would  be  present  in  the  amount  of  liquor  taken  for  titration 
and  divide  by  0.007806.  This  will  give  the  number  of  cc.  of  0.1  N  HC1 
required  by  the  Na2S.  Subtract  this  from  the  total  titration  and  calculate 
the  difference  to  NaOH. 

Sodium  Carbonate. — Pipette  25  cc.  of  the  original  liquor  into  a 
white  casserole  and  add  200  cc.  of  distilled  water.  Titrate  with 
0.5  N  HC1  and  methyl  orange.  This  titration  gives  the  alkalinity 
due  to  Na2COs,  NaOH,  and  Na2S.*  Subtract  the  equivalents  of 
NaOH  and  Na2S  previously  determined  and  calculate  the  differ- 
ence to  Na2COs. 

CALCULATION.— 1  cc.  0.5  N  HC1  =  0.02650  gram  Na2CO3. 

Sodium  Silicate. — The  sodium  silicate  may  be  approximately 
calculated  by  multiplying  the  amount  of  Si02  by  1.257.  This  is 
for  the  formula  Na2Si409.  In  the  presence  of  considerable  amounts 
of  sodium  silicate  the  method  of  analysis  is  complicated  and 
results  by  the  above  procedures  are  not  strictly  correct  as  regards 
NaOH  and  Na2CO3. 

Total  Alkalinity. — The  total  alkalinity  of  the  liquor  itself  is 
obtained  by  direct  titration  with  standard  acid  and  methyl  orange 
*  Also  one-half  of  Na2SO3,  if  the  latter  is  present. 


298  TECHNICAL  METHODS  OF  ANALYSIS 

as    described  under   the    determination   of   Sodium    Carbonate. 
Calculate  the  titration  as  Na2O  and  also  as  NaOH. 

CALCULATION.— 1  cc.  of  0.5  N  acid  =  0.01550  gram  Na2O. 

=  0.02001  gram  NaOH. 

WHITE  LIQUOR 

General. — The  determination  of  total  solids,  ash,  total  sodium 
and  available  alkalinity  are  not  generally  required  on  white  liquor, 
but,  if  desired,  may  be  made  by  the  same  procedures  as  described 
under  Black  Liquor. 

Specific  Gravity. — Determine  as  under  Black  Liquor. 

Sodium  Silicate  and  Silica. — Pipette  50  cc.  into  a  platinum  dish, 
add  cautiously  an  excess  of  HC1,  evaporate  to  dryness,  and  then 
bake  for  one  hour  or  more  at  120°  C.  Take  up  with  HC1,  dilute 
with  water,  filter,  wash  with  hot  water,  ignite  the  residue  in  plat- 
inum with  a  blast  lamp  and  weigh  as  SiO2.  An  approximation  of 
the  sodium  silicate  (Na^uOo)  present  may  be  obtained  by  mul- 
tiplying the  SiO2  thus  found  by  1.257. 

Sodium  Sulfate. — Determine  as  under  Black  Liquor.  The 
Na2SC>4  should  be  present  only  as  an  impurity. 

Sodium  Sulfide. — Pipette  25  cc.  of  the  liquor  into  a  dry 
beaker  of  about  300  cc.  capacity.  Do  not  dilute  with  water. 
Run  in  from  a  burette  an  amount  of  ammoniacal  AgNOa 
solution  as  close  to  the  saturation  point  as  can  be  estimated.  (This 
can  be  done  from  a  preliminary  titration.)  Then  shake  the  con- 
tents of  the  beaker  rather  vigorously  for  two  or  three  seconds. 
This  causes  the  black  Ag2S  to  separate  in  thick  lumps  from  the 
clear  solution.  Add  another  drop  of  the  AgNOs  solution  from  the 
burette.  If  this  forms  a  heavy  precipitate  where  the  drop  comes 
in  contact  with  the  solution,  add  a  few  more  drops,  give  the  beaker 
a  shake  and  repeat  the  additions  until  only  a  faint  cloud  appears 
in  the  clear  solution.  If  the  beaker  is  held  over  a  white  sheet  of 
paper,  the  end  point  may  be  easily  determined  within  a  single  drop. 
The  last  drop  necessary  to  complete  the  precipitation  forms  only  a 
faint  cloud  in  the  clear -solution.  If  then  another  drop  is  run  in 
after  shaking,  instead  of  forming  a  faint  dark  cloud,  it  will  remain 
as  a  clear  colorless  spot  surrounded  by  the  faintly  distributed  pre- 
cipitate in  the  pale  brownish  solution. 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       299 

NOTE. — If  the  silver  solution  is  added  in  excess  it  will  all  be  distributed 
evenly  through  the  solution  and  no  amount  of  shaking  will  cause  it  to  separate 
in  lumps. 

A ryimoniacal  Silver  Nitrate  Solution.— Dissolve  55.29  grams  of 
pure  metallic  silver  in  pure  HNOa,  or  dissolve  87.07  grams  of 
pure  AgNOs  in  water.  Then  add  250  cc.  of  cone.  NH^OH  and 
dilute  to  1  liter.  (Keep  protected  from  strong  light  and  away  from 
heat.)  1  cc.  of  this  solution  is  equivalent  to  0.02  gram  of  Na2S. 

Alkalinity. — (A)  TOTAL  ALKALI  EXPRESSED  IN  TERMS  OF 
NA20. — Pipette  out  25  cc.  of  the  liquor  and  titrate  with  0.5  N 
acid  and  methyl  orange.  The  number  of  cc.  of  acid  used  (call  this 
A)  represents  the  alkali  existing  in  the  solution  as  Na2COs,  NaOH, 
Na2S,  and  one-half  Na2S03.  Calculate  it  in  terms  of  Na2O. 

CALCULATION. — 1  cc.  0.5  N  acid  =  0.01550  gram  Na2O. 

(B)  SODA  AS  NAOH+NA2S.— Pipette  25  cc.  of  the  sample 
into  a  100  cc.  graduated  flask.     Add  25  cc.  of  a  10%  solution  of 
BaCl2  and  make  up  to  the  mark  with  freshly  boiled  distilled 
water.     Shake  for  a  few  minutes  and  let  settle.     Cool  and  draw 
off  50  cc.  of  the  clear  liquid  and  titrate  with  0.5  N  acid  and  methyl 
orange.     The  number  of  cc.  multiplied  by  2  indicates  the  amount 
of  acid  necessary  to  neutralize  the  NaOH  and  Na2S  in  the  sample. 
(Call  this  B.)     The  difference  between  A  and  B  represents  the 
number  of  cc.  required  to  neutralize  the  Na2COs  and  one-half  the 
Na2SOs,  barium  sulfite  being  practically  insoluble. 

(C)  SODA   AS   SULFIDE,    SULFITE  AND  THIOSULFATE. — Make 
a  rough  titration  of  10  cc.  of  the  liquor  with  0.1  N  iodine,  after 
acidifying  with  acetic  acid.     Then  run  out  from  a  burette  0.5  cc. 
less  than  the  required  amount  of  iodine  into  a  beaker  containing 
about  200  cc.  of  distilled  oxygen-free  water.     Pipette  into  the  mix- 
ture 10  cc.  of  the  liquor,  make  acid  with  acetic  acid  and  complete 
the  titration  with  0.1  N  iodine,  using  starch  as  indicator.     This 
titration  indicates  the  amount  of  Na2S,  Na2S2Os  and  Na2SOa 
in  the  sample.     (Call  this  titration  C.) 

CALCULATION. — 1  cc.  0.1  N  iodine  =  0.003903  gram  Na2S. 

=  0.003100  gram  Na2O. 

(D)  SODIUM  THIOSULFATE  AND  SULFITE. — Pipette  50  cc.  of 
the  liquor  into  a  graduated  250  cc.  flask.     Add  an  excess  of  an 
alkaline  solution  of  zinc  chloride  (made  by  adding  NaOH  to  a 


300  TECHNICAL  METHODS  OF  ANALYSIS 


solution  in  sufficient  excess  to  redissolve  the  precipitate 
formed).  Make  up  to  the  mark,  shake  for  a  few  minutes  and  let 
settle.  Draw  off  100  cc.  of  the  clear  solution  with  a  pipette  and 
neutralize  with  0.1  N  H2SO4,  using  methyl  orange.  This  converts 
the  sulfites  present  into  acid  sulfites.  When  acid  sulfites  are 
titrated  with  iodine  the  following  reaction  takes  place: 


Hence  1  molecule  of  acid  sulfite  on  titration  with  iodine  liberates 
acid  equivalent  to  3  molecules  of  NaOH. 

Titrate  the  neutralized  solution  with  0.1  N  iodine  solution  and 
starch.  (Call  this  D.)  Then  decolorize  with  1  drop  of  0.1  N 
thiosulfate  solution  and  titrate  till  neutral  with  0.1  N  NaOH.  The 
number  of  cc.  of  NaOH,  multiplied  by  0.0042,  gives  the  amount  of 
Na2SOs  in  the  aliquot;  and  this  figure,  divided  by  0.0063,  gives  the 
number  of  cc.  of  0.1  N  iodine  to  which  it  is  equivalent.  Subtract 
this  from  the  iodine  titration  previously  obtained.  Calculate  the 
difference  to  sodium  thiosulfate. 

CALCULATION.  —  1  cc.  0.1  N  iodine  =  0.01581  gram  Na2S2Os. 

(E)  FINAL  CALCULATIONS.  —  C—  —  gives  the  cc.  of  iodine  equiv- 

2 

alent  to  the  Na2S.  (This  is  a  check  on  the  Na2$  by  ammoniacal 
AgN03.) 

A-B  gives  the  number  of  cc.  required  by  the  Na2COs  and 
one-half  the  Na2SOa. 

1  cc.  0.1  N  iodine  =  0.003903  gram  Na2S. 

1  cc.  0.5  N  acid      =0.02650  gram  Na2C03. 
=  0.01550  gram  Na2O. 

The  titration  B,  expressed  as  Na20,  minus  the  sodium  sulfide 
titration  (with  ammoniacal  AgNOs),  expressed  as  Na20,  gives  the 
Na2O  present  as  NaOH.  Calculate  this  to  NaOH  by  multiply- 
ing by  1.291. 

NOTE.  —  The  above  methods  under  Alkalinity  are  those  of  Otto  Kress  pub- 
lished in  Paper,  17,  No.  24,  page  30  (1916). 

REFERENCES.  —  The  method  for  Sulfide  in  White  Liquor  is  described  by 
Carl  Moe  in  Paper,  14,  No.  22,  page  19  (1914).  See  also  article  by  Otto 
Kress  in  Paper,  17,  No.  24,  page  30  (1916);  and  articles  by  Carl  Moe  begin- 
ning in  Paper,  18,  No.  12,  page  11  (1916),  and  by  the  same  author  in  Paper, 
13,  No.  24,  page  156  (1913). 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       301 

SULFITE  ACID 

General.— "  Sulfite  Acid  "  or  "  Bisulfite  Liquor  "  is  the  liquid 
used  for  cooking  wood  to  make  pulp  by  the  well-known  sulfite 
process.  It  consists  of  an  aqueous  solution  of  calcium  and  mag- 
nesium bisulfites  with  an  excess  of  sulfurous  acid.  As  the  SO 2 
gas  from  which  it  is  made  always  contains  a  little  80s,  the  fin- 
ished acid  liquor  will  contain  more  or  less  CaS04  as  an  impurity. 

Specific  Gravity. — Determine  with  the  Westphal  balance 
or  by  the  pycnometer,  preferably  the  former. 

Total  Sulfurous  Acid. — Measure  out  10  cc.  of  the  acid  and 
make  up  to  100  cc.  in  a  graduated  flask.  Pipette  10  cc.  of  the 
diluted  acid  into  an  excess  of  0.1  N  iodine  and  titrate  with 
0.1  N  thio,  using  starch  solution  as  an  indicator.  Calculate 
to  SO2. 

CALCULATION. — 1  cc.  0.1  N  iodine  =  0.0032  gram  SCb. 

Free  Sulfurous  Acid. — Titrate  25  cc.  of  the  diluted  solution 
with  0.5  N  KOH,  using  phenolphthalein  as  an  indicator.  Cal- 
culate to  SC>2. 

CALCULATION.— 1  cc.  0.5  N  KOH  =  0.016  gram  SO2. 

Sulfuric  Acid. — Measure  out  25  cc.  of  the  original  solution,  add 
a  slight  excess  of  HC1  and  boil  until  the  862  is  completely  expelled. 
To  the  boiling  solution  add  10%  BaCk  solution,  drop  by  drop,  in 
excess.  Boil  for  thirty  minutes,  let  stand  till  clear,  filter,  ignite 
and  weigh  as  BaSO4.  Calculate  to  80s. 

CALCULATION.— BaSO4  X  0.3430  =  SO3. 

Lime  and  Magnesia. — Pipette  out  25  cc.  of  the  original  solu- 
tion, add  about  1  cc.  of  cone.  H2SO4,  evaporate  to  dryness  in  a 
platinum  dish,  ignite  carefully,  cool  and  weigh  the  mixed  sulfates 
as  CaSO4  and  MgS04. 

Dissolve  the  residue  in  25  cc.  of  dil.  HC1,  wash  the  solution 
into  a  beaker,  make  alkaline  with  NKiOH,  heat  to  boiling  and 
add  enough  (NILi)2C204  solution  to  completely  precipitate  the 
lime.  Continue  the  boiling  for  two  minutes,  and  let  the  precipitated 
CaC2O4  settle  for  one-half  hour.  Filter,  wash  with  hot  water, 
ignite  in  a  platinum  crucible  over  a  blast  lamp  to  constant  weight 
and  weigh  as  CaO.  Calculate  the  CaO  to  CaSO4,  deduct  from  the 
mixed  sulfates  and  calculate  the  MgSO4  to  MgO. 

CALCULATION.— CaO  X  2.4279     =  CaSO4. 
MgS04X  0.3349  =  MgO. 


302  TECHNICAL  METHODS  OF  ANALYSIS 

NOTE. — The  Ca  and  Mg  sulfates  may  also  be  separated  as  follows:  Add 
10  cc.  of  water  and  1  or  2  drops  of  HC1,  which  will  dissolve  all  the  MgSO4. 
Add  1  or  2  drops  of  cone.  H2SO4  and  25  cc.  of  95%  alcohol.  Let  stand  for  one 
hour,  filter  and  wash  with  60%  alcohol  to  remove  acid.  Finally  wash  with 
40%  alcohol  as  long  as  anything  is  dissolved.  Ignite  and  weigh  as  CaSO4. 

Results. — The  results  should  be  expressed  as  follows: 

Sulfurous  Acid  (SO2) 
Sulfuric  Acid  (SO3) 
Lime  (CaO) 
Magnesia  (MgO) 
Equivalent  to: 

Calcium  Sulfate  (CaS04) 
Calcium  Bisulfite  (CaS2O5) 
Magnesium  Bisulfite  (MgS2O5) 
Free  Sulfurous  Acid  (802). 

The  80s  is  calculated  to  CaSO4.  The  remaining  CaO  is  cal- 
culated to  CaS205  and  the  MgO  is  calculated  to  MgS2O5.  The 
excess  SO2  is  expressed  as  free  S02. 

The  so-called  "Mill  Test  "  is  expressed  as  follows: 

"  Free  "  Sulfurous  Acid. 

"  Combined  "  Sulfurous  Acid. 

Total  Sulfurous  Acid. 

The  "  free  "  sulfurous  acid  is  the  actual  free  S02  plus  one-half 
of  the  SO2  in  the  CaS2Os  plus  one-half  of  the  SO2  in  the 
MgS2O5,  and  should  check  approximately  with  the  figure  obtained 
by  the  titration  with  KOH.  It  is,  more  strictly  speaking,  the 
"  available  SO2.  "  The  "  combined  "  sulfurous  acid  is  the  sum 
of  one-half  of  the  SO2  in  the  CaS2Os  and  one-half  of  the  SO2  in 
the  MgS205. 

NOTES. — (1)  The  "  free  "  and  "  combined  "  SO2  together  should  be  the 

same  as  the  total  SO2  determined  by  titration  with  iodine. 

(2)  Griffin   and  Little  ("The  Chemistry  of  Paper  Making,"   page  228) 

give  the  following  as  a  typical  analysis  of  a  well-made  liquor  prepared  from 

dolomite : 

Sp.  gr.  at  15°  C 1.0582 

Total  S02 4.41% 

SO3 0.13% 

CaO 0.95% 

MgO 0.72% 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       303 

Combined  as: 

CaSO4 0.22% 

CaS205 2.84% 

MgS2O5 3.04% 

Free  SO2 0.11% 

This  would  give  a  "  Mill  Test  "  as  follows: 

Free  SO2 2.26% 

Combined  SO2 2. 15% 

Total  S02 4.41% 

The  tendency  to-day  is  toward  a  high  "free  S02,"  2.50-3.20%,  and  a 
lower  combined  SO2,  1.20-1.35%.  For  cooking  dry  wood  a  suitable  ratio 
is  (approximately): 

Total  SO2:  "free"  S02:  "combined"  SO2=4  :  3  :  1. 

For  wet  wood  the  "  combined  "  SO2  should  be  higher. 

Factors. — The  following  factors  will  be  found  useful  in  cal- 
culating the  final  combinations: 

SO3X  1.700  =CaSO4. 

CaOX  3.285  =CaS2O5  . 

MgOX4.178  =  MgS205. 

CaS2O5X0.6956  =  SO2. 

MgS205X  0.7606  =  S02. 

ALUM 

General. — This  method  is  for  the  "  alum  "  used  by  paper- 
makers,  which  is  not  a  true  alum  but  a  sulfate  of  alumina, 
A12(S04)3-18H2O. 

Insoluble  Matter. — Dissolve  25  grams  of  the  sample  in  about 
200  cc.  of  boiling  water  and  filter  rapidly  through  a  weighed 
Gooch  crucible  with  suction.  Wash  the  residue  on  the  filter  with 
hot  water,  dry  at  105°  C.  and  weigh. 

SOLUTION  No.  1. — Transfer  the  filtered  solution  to  a  500  cc. 
volumetric  flask,  cool,  dilute  to  500  cc.  and  thoroughly  mix. 

SOLUTION  No.  2. — Transfer  100  cc.  of  Solution  No.  1,  equiva- 
lent to  5  grams  of  alum,  to  another  500  cc.  flask,  make  up  to  the 
mark  with  distilled  water,  and  thoroughly  mix. 

Alumina. — Pipette  out  50  cc.  of  Solution  No.  2,  equivalent  to 
0.5  gram  of  alum,  and  acidify  with  10  cc.  of  cone.  HG1  and  4-5 
drops  of  cone.  HNO3.  Heat  to  boiling.  Add  10  cc.  of  10% 


304  TECHNICAL  METHODS  OF  ANALYSIS 

NBUC1  solution  and  a  pinch  of  tannic  acid  on  the  end  of  a  spatula, 
and  then  NELiOH  until  barely  alkaline.  Boil  until  there  is  only 
a  faint  smell  of  NHs.  Let  the  precipitate  settle,  filter  and  wash 
free  from  chlorides.  Dry  the  precipitate  in  the  oven  in  a  weighed 
platinum  crucible,  then  ignite  over  a  blast  lamp  to  constant 
weight,  and  weigh  as  Fe203+Al203.  To  obtain  the  amount  of 
alumina,  determine  the  Fe20s  separately  as  below  and  deduct 
from  this  weight.  , 

Sulfuric  Acid.— Acidify  100  cc.  of  Solution  No.  2  with  HC1 
and  heat  to  boiling.  Then  add  10%  BaCl2  solution  slowly,  drop 
by -drop,  as  long  as  it  produces  a  precipitate.  Boil  one-half  hour. 
(Or,  boil  five  minutes  and  let  stand  overnight.)  Let  the  precipitate 
settle  completely,  filter,  ignite  and  weigh  as  BaSC>4.  (Test  the 
filtrate  with  more  BaCb  to  insure  complete  precipitation.)  Cal- 
culate to  80s. 

CALCULATION.— BaSO4  X  0.3430  =  S03. 

Iron. — Transfer  100  cc.  of  Solution  No.  1  to  a  200  cc.  beaker 
and  add  5  cc.  of  cone.  H2SO4  and  0.1  N  KMn(>4,  drop  by  drop,  till  a 
permanent  pink  forms.  Pass  this  solution  through  the  Jones 
reductor  (see  page  148)  and  titrate  to  a  faint  pink  with  0.1  N 
KMnC>4  solution.*  Calculate  the  iron  as  Fe2Os. 

CALCULATION.— 1  cc.  0.1  N  KMnO4  =  0.008  gram  Fe2O3. 

NOTE. — In  case  it  is  impossible  to  get  the  reductor  so  that  a  single  drop  of 
KMnO4  will  color  the  washing  solution,  run  a  "  blank  "  on  the  reductor 
using  the  same  amounts  of  reagents  and  washings  and  subtract  the  "  blank  " 
titration  from  the  titration  required  by  the  sample. 

Zinc. — Add  (NH^S  in  excess  to  the  filtrate  from  the  AkOa 
precipitate  and  let  stand  some  time.  Filter,  wash  with  H2S 
water  and  dissolve  the  ZnS  precipitate  in  dil.  HC1.  Make  alkaline 
with  NHiOH,  add  1  drop  of  litmus  solution  and  HNOs  until 
the  litmus  just  turns  red.  Heat  nearly  to  boiling  and  add  slowly 
ammonium  phosphate  solution  containing  a  weight  of  phosphate 
equal  to  12  times  that  of  the  Zn  to  be  precipitated.  Keep  the 
solution  just  below  boiling  point  for  about  fifteen  minutes,  or  until 
the  precipitate  has  become  crystalline.  Let  the  solution  cool  for 

*  For  alums  containing  a  very  small  amount  of  Fe  use  0.01  N  KMnO4 
for  titrating  both  the  sample  and  the  "  blank."  If  extreme  accuracy  is  desired 
a  larger  sample  may  be  used. 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS      305 

at  least  four  hours  and  then  filter  on  a  Gooch  crucible.  Wash 
with  a  1%  solution  of  ammonium  phosphate  until  free  from  sul- 
fate,  then  wash  5  times  with  alcohol.  Dry  at  105°  C.  to  constant 
weight  and  weigh  as  ZnNHiPCX.  (It  may  also  be  ignited  and 
weighed  as  Zn2P207.) 

Complete  precipitation  of  the  Zn  depends  on  the  neutrality 
of  the  solution  and  it  is  absolutely  necessary  to  test  the  filtrate 
for  Zn  by  adding  NKUOH  and  a  few  drops  of  (NILi)2S  and  allowing 
it  to  stand  for  some  time. 

CALCULATION.—  ZnNH4PO4  X  0.3663  =  Zn. 
Zn2P2O7X  0.4289  =  Zn. 

Lime.  —  Boil  the  filtrate  from  the  Zn  precipitate  to  expel  H2S, 
make  alkaline  with  NH^OH  and  add  (NH4)2C2O4  solution  in 
excess.  Filter,  wash,  ignite  in  the  blast  and  weigh  as  CaO. 

Basicity  or  Acidity.  —  The  following  method  *  is  based  on  the 
fact  that  an  excess  of  neutral  KF  decomposes  aluminum  salts, 
forming  two  stable  compounds  reacting  neutral  to  phenolphtha- 
lein,  while  any  free  acid  remains  unaltered,  thus: 


SOLUTIONS  REQUIRED.  —  (1)  0.1%  alcoholic  solution  of  phenol- 
phthalein. 

(2)  KF    solution,    prepared    by   dissolving    1000    grams   of 
pure  KF  in  1200    cc.  of   hot    CO2-free    distilled    water,  adding 
5  cc.  of  phenolphthalein  solution  and  neutralizing  if  necessary 
with  KOH  or  H2SO4  (or  HF)  until  about  1  cc.  in  10  cc.  of  dis- 
tilled water  shows  a  faint  pink  color.     Filter  out  any  insoluble 
matter  without  washing  and  dilute  the  clear  nitrate  to  2000  cc. 
with  C02-free  water.     Preserve  in  a  wax  bottle  or  a  glass  bottle 
coated  inside  with  wax. 

(3)  Standard  0.5  N  #2S04  and  0.5  N  KOH,  free  from  A12O3 
and  similar  bases.     Standardize  the  alkali  against  the  acid  in 
about  40  cc.  of  distilled  water  to  which  10  cc.   of  the  above  KF 
solution  have  been  added,  using  phenolphthalein  indicator. 

PROCEDURE.  —  Place  exactly  68  cc.  of  Solution  No.  1,  equivalent 
to  3.40  grams  of  sample,  in  a  4-inch  casserole.     Add  about  35  cc. 
of  distilled  water  and  heat  to  boiling.     To  the  solution  add  exactly 
*  J.Soc.  Chem.  Ind.  30,  184  (1911). 


306  TECHNICAL  METHODS  OF  ANALYSIS 

10  cc.  of  0.5  N  H2S04.  Cool  to  room  temperature;  add  18-20  cc. 
of  KF  solution  and  0.5  cc.  of  phenolphthalein  solution.  Titrate 
with  0.5  N  KOH  (do  not  use  NaOH),  adding  it  drop  by  drop  until 
a  slight  pink  persisting  for  one  minute  is  obtained.  The  titration 
shows  whether  the  material  is  basic  or  acid  as  follows : 

Basic  AhOz. — When  the  KOH  back  titration  is  less  than  the 
amount  of  H2SO4  added,  then 

Free  A1203  =  (cc.  of  H2S04— cc.  of  KOH)  X0.25. 

Free  #2$04. — When  the  KOH  back  titration  is  greater  than 
the  amount  of  H2SO4  added,  then 

Free  H2S04  =  (cc.  of  KOH— cc.  of  H2S04)X0.72. 

Neutrality. — If  the  back  titration  is  equal  to  the  H2SO4  added, 
then  the  alum  is  neutral. 

NOTE. — Darkening  of  the  solution  during  the  back  titration  with  KOH 
indicates  an  insufficient  amount  of  KF  added.  In  such  cases,  repeat  the  test 
with  a  fresh  solution  and  a  larger  amount  of  KF.  Ammonium  salts  if  present 
must  be  expelled  by  boiling  the  sample  with  an  excess  of  standard  KOH  and 
this  excess  determined.  Also  if  much  iron  salts  are  present,  an  increased 
quantity  of  KF  solution  may  be  required. 

CALCULATION  OF  RESULTS. — It  is  seldom  that  papermakers' 
alum  contains  Zn  or  more  than  traces  of  lime,  titanium,  etc. 
Under  ordinary  circumstances  the  results  should  be  reported  as 
follows: 

Insoluble  Matter 

Alumina  (A^Os)  (soluble  in  water) 

Sulfuric  Acid  (S03) 

Iron,  calculated  as  Ferric  Oxide  (Fe20s) 

Equivalent  to : 

Insoluble  Matter 
Ferrous  Sulfate  (FeS04) 
Aluminum  Sulfate  [Al2(S04)a] 
Basic  Alumina  (Al2Oa)* 
Water  (by  difference). 

The  Fe20s  is  all  calculated  to  FeSO4,  although  as  a  matter  of  fact 
more  or  less  of  it  is  generally  present  in  the  oxidized  state.     The 
*  Or,  Free  Sulfuric  Acid  (H2SO4). 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       307 

remaining  SO3  is  calculated  to  Ab (804)3.  Any  A1203  left  over  is 
reported  as  basic  A12O3.  In  case  the  sample  contains  free  acid, 
the  Fe2O3  is  calculated  to  FeSC>4  as  above,  the  total  A1203  to 
Ah (864)3,  and  the  remaining  80s  to  free  H2S04. 

Factors. — The  following  factors  will  be  found  useful: 

Fe203X  1.9026       =FeSO4. 

A12O3  X  3.3503        =  A12(SO4)3. 

A12(S04)3  X0.2985  =  A12O3. 

A12(SO4)3X0.7015  =  SO3. 

Fe2O3X  1.0028       =SO3  in  equiv.  am't  of  FeS04. 

80s  X  1.2251  =H2S04. 

ANILINE  DYES 

General. — This  method  is  for  the  testing  of  aniline  dyes  for 
use  in  coloring  paper. 

Solutions. — (A)  The  stock  should  be  made  up  from  bleached 
sulfite  pulp  to  contain  1  gram  of  dry  fiber  to  200  cc.  of  water. 
Add  2.5%  of  rosin  and  5.0%  of  alum  *  to  the  stock  in  the  beater 
and  beat  into  the  pulp. 

(B)  The  dye  solutions  should  be  made  up  in  the  ratio  of  1 
gram  of  dye  in  2000  cc.  of  water.     (500  cc.  make  a  convenient 
amount  to  handle.)     In  making  up  the  dye  solution,  add  the 
weighed  powder  to  about  100  cc.  of  water  in  a  250  cc.  beaker 
and  boil  very  gently  for  a  few  moments.     Rinse  into  a  500  cc. 
graduated  flask  and  dilute  to  the  mark. 

(C)  Dilute   solutions   of  sodium   chloride,   lead   acetate  and 
soda  ash  are  also  required  as  mordants  for  certain  colors. 

Procedure. — Take  200  cc.  of  the  stock  solution  in  a  finger  bowl 
or  other  container  of  similar  shape,  and  add  the  dye  solution  from  a 
pipette.  The  strength  of  dye  to  use  depends  both  on  the  class 
and  the  individual  characteristics  of  the  color.  In  general  the 
following  is  a  guide : 

For  basic  colors,  from  0.5-0.20%  of  the  weight  of  dry 
fiber. 

For  acid  and  direct  colors,  about  0.25%  of  the  weight  of  dry 
fiber. 

*  Paper-makers'  alum,  Al2(SOo)3-18H2O.  Both  of  these  percentages  are 
based  on  the  weight  of  dry  fiber. 


308  TECHNICAL  METHODS  OF  ANALYSIS 

The  stronger  the  tinctural  power,  the  smaller  is  the  percentage 
required. 

Make  up  two  lots  of  equal  proportions  of  the  laboratory  stand- 
ard and  of  the  sample  under  examination.  Also  make  up  several 
standards  with  10%  differences  in  strength  of  dye,  as  70%,  80%, 
90%,  110%,  etc. 

Form  the  sheets  by  the  use  of  a  hand  mold.  After  forming 
the  sheet  couch  it  on  a  strip  of  absorbent  paper,  fold  the  absorbent 
paper  over  the  sheet  and  mark  it  with  the  strength  of  the  dye. 
Squeeze  out  the  surplus  moisture  by  passing  through  a  wringer. 
Remove  the  dyed  sheet,  punch  a  hole  near  the  edge  and  suspend 
it  on  a  copper  wire  or  glass  rod  in  the  drying  oven  at  a  temperature 
of  about  85°  C. 

After  the  samples  are  entirely  dry,  they  should  be  compared, 
getting  the  light  from  different  angles  and  noting  both  sides  of 
sheets.  It  will  be  found  an  easy  matter  to  decide  which  of  the 
standard  samples  is  the  nearest  match  and  the  whole  procedure 
should  then  be  repeated,  making  up  standards  varying  by  5% 
each  side  of  the  one  most  nearly  matching  the  dye  under  examina- 
tion. 

Results  are  to  be  reported  as : 

X  parts  sample  =  Y  parts  standard 
(X  preferably  being  equal  to  100). 

NOTES. — (1)  A  convenient  method  of  permanently  marking  sample  sheets 
is  to  use  an  indelible  pencil  after  passing  the  sheets  through  the  wringer. 

(2)  In  testing  the  yellow  dyes,  it  is  a  help  to  add  methylene  blue  or  safra- 
nine,  using  a  constant  quantity  of  about  25%  of  the  amount  of  yellow  used. 
Samples  so  made  are  compared  for  shade  rather  than  strength. 

(3)  This  method  was  submitted  by  H.  P.  Carruth  in  1911. 


BLANC  FIXE 

General. — Blanc  Fixe  is  generally  marketed  as  a  paste  of 
BaSO4  and  water,  less  commonly  in  the  dry  form.  The  com- 
mercial blanc  fixe  often  also  contains  more  or  less  phosphate  and 
impurities  such  as  carbonates,  sulfites,  organic  matter,  silica, 
heavy  metals  and  alkali  metals.  It  is  quite  often  the  case  that  a 
blanc  fixe  is  practically  pure  as  it  leaves  the  factory  but  takes  up 
impurities  on  standing  in  the  storage  barrels.  It  is  claimed  that 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       309 

it  is  bad  to  store  it  in  oak  barrels,  as  a  yellow  stain  nearly  always 
develops.  It  should  preferably  be  stored  in  fir  barrels. 

Blanc  fixe  in  the  pulp  form  (paste)  should  not  contain  more 
than  30%  of  moisture,  and  both  pulp  and  dry  forms  should  con- 
tain not  less  than  97.5%  of  BaS04  on  the  dry  basis. 

As  a  general  rule  the  determination  of  water,  organic  and 
volatile  matter,  and  total  BaSCX  is  sufficient,  but  it  is 
sometimes  desirable  to  determine  the  amount  and  nature  of 
the  impurities  and  accordingly  the  following  complete  scheme 
is  given. 

Qualitative  Tests. — As  the  source  of  raw  materials  and  methods 
of  manufacture  determine  the  presence  of  certain  impurities,  a 
qualitative  analysis  should  be  made  before  proceeding  with  the 
quantitative  determination. 

Where  the  blanc  fixe  is  intended  solely  for  photographic  pur- 
poses, test  the  sample  first  with  AgNOs  as  follows :  Spread  a  small 
sample  on  a  glass  plate  with  a  spatula  and  apply  a  drop  of  10% 
AgNOs  solution.  If  a  deep  brown  or  blackish  stain  develops 
within  five  minutes  in  the  dark,  the  sample  is  unfit  for  photo- 
graphic purposes.  Failure  to  meet  this  test,  however,  does  not 
disqualify  it  as  a  filler  or  for  coating  ordinary  paper. 

Organic  Matter. — A  rough  qualitative  test  for  organic  matter 
is  to  heat  about  1  gram  in  a  test-tube  with  5-10  cc.  of  cone.  H2SO4 
and  let  settle.  If  organic  matter  is  present  the  acid  will  turn  brown. 

Silica. — If  a  half  gram  sample  dissolves  completely  in  5-10 
cc.  of  hot  cone.  H2SO4  the  absence  of  SiO2  is  indicated. 

Lead. — Boil  5  grams  with  saturated  ammonium  acetate 
solution  and  filter.  To  the  filtrate  add  a  solution  of  K^C^O?. 
A  yellow  precipitate  indicates  Pb. 

Iron  and  Alumina. — Heat  5  grams  with  25  cc.  of  HNOs  (1  :  1) 
and  filter.  Add  a  slight  excess  of  NKLjOH  to  the  filtrate  and 
heat.  A  flocculent  precipitate  indicates  alumina,  if  white,  and 
iron  and  alumina,  if  brownish. 

Alkalies. — Tests  for  the  alkalies  and  ammonia  are  made  on 
the  water  solution  in  the  usual  way. 

Moisture. — Weigh  out  rapidly  5  grams  of  the  sample  and  dry 
to  constant  weight  at  100°  C.  Report  the  loss  as  moisture. 

Loss  on  Ignition. — Ignite  strongly  the  residue  from  the  moisture 
determination,  cool  in  a  desiccator  and  weigh.  The  loss  indicates 


310  TECHNICAL  METHODS  OF  ANALYSIS 

organic    and    volatile    matter.     Previous    qualitative    tests    will 
indicate  whether  a  part  of  this  loss  is  due  to  carbonate. 

Water-soluble  Material. — Digest  5  grams  of  the  sample  in 
150  cc.  of  hot  water.  Filter  and  wash  with  hot  water.  Evap- 
orate the  filtrate  to  dryness  in  a  weighed  platinum  dish  and  dry 
to  constant  weight  at  100°  C. 

Acid-soluble  Material. — Transfer  the  residue  on  the  filter 
paper  from  the  water-soluble  determination  to  the  beaker  con- 
taining the  remaining  residue,  and  treat  the  whole  with  125  cc. 
of  hot  HC1  (1  :  3).  Filter  and  wash.  Evaporate  the  filtrate 
and  washings  to  dryness  in  a  weighed  platinum  dish  and  dry  at 
100°  C.  to  constant  weight. 

Iron  Oxide  and  Alumina. — If  the  acid-soluble  material  is  high, 
the  presence  of  Fe2O3,  A1203,  BaCO3  or  Ba3(PO4)2  is  indicated. 
If  phosphate  is  absent,  take  up  the  acid  soluble  residue  with  a 
little  HC1  and  100  cc.  of  water.  Make  the  solution  slightly 
alkaline  with  NE^OH;  filter,  wash  with  hot  water,  and  ignite  the 
precipitate,  finally  with  a  blast  lamp;  cool  in  a  desiccator,  and 
weigh  as  Al2O3+Fe2O3.  If  phosphate  is  present,  add  to  the  acid 
solution  a  known  amount  of  Fe203  in  the  form  of  chloride  or  sul- 
fate  (see  page  25),  then  make  slightly  -alkaline  with  NHiOH 
and  proceed  as  above.  Subtract  the  known  amount  of  Fe2Os 
added.  The  resulting  figure  wiU  be  Fe2O3+Al2O3+P205  in 
the  sample.  Determine  the  P2Os  on  a  separate  portion  by  the 
molybdate  method  as  described  below,  and  subtract  to  get 
Fe2O3-t-Al203. 

Barium  Carbonate  (and  Phosphate). — To  the  filtrate  from  the 
above  add  a  slight  excess  of  HC1,  heat  to  boiling,  and  then  add 
slowly  an  excess  of  dil.  H2SO4.  Boil  until  the  precipitate  settles 
clear;  filter,  ignite,  cool  in  a  desiccator  and  weigh  as  BaSO4. 
Calculate  to  BaC03  or  Ba3(PO4)2  according  to  the  qualitative 
analysis. 

CALCULATIONS.— BaSO4  X  0.8456  =  BaCO3. 

BaSO4  X  0.8599  =  Ba3  (PO4)2. 

Lime  and  Magnesia. — These  are  not  often  present  in  com- 
mercial blanc  fixe  but  may  be  determined  in  the  filtrate  from  the 
barium  carbonate  above  in  the  usual  way. 

Lead  Sulfate. — If  the  qualitative  tests  showed  lead,  boil  with 
saturated  ammonium  acetate  solution  the  sulfate  residue  from 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       311 

the  acid  soluble  treatment.  Filter  and  wash.  Add  a  few  drops 
of  acetic  acid  and  then  a  slight  excess  of  bichromate  solution. 
Heat  to  boiling,  filter  through  a  weighed  Gooch  crucible,  wash 
with  hot  water,  dry  at  about  100°  C.,  set  the  Gooch  crucible  in  a 
larger  platinum  crucible,  ignite  gently  and  weigh  as  PbCr04.  Cal- 
culate to  PbSO4. 

CALCULATION.— PbCr04X  0.9383  =  PbSO4. 

Barium  Sulfate. — Dry  the  residue  from  the  ammonium  acetate 
treatment  (or,  if  Pb  is  absent,  the  residue  from  the  acid  soluble 
treatment)  to  constant  weight  and  calculate  its  percentage  of  the 
original  sample.  Then  weigh  out  1  gram  of  this  dry  residue, 
mix  with  5-7  grams  of  pure  Na2COs  and  fuse  in  a  platinum 
crucible  to  a  thin  liquid.  Digest  the  fusion  with  hot  water  until 
completely  disintegrated;  filter  and  wash  thoroughly  with  hot 
water.  Make  the  filtrate  slightly  acid  with  dil.  HC1,  dilute  to 
350  cc.  and  heat  to  boiling.  Then  add  25  cc.  of  10%  BaCl2 
solution,  drop  by  drop  from  a  pipette.  Boil  for  five  minutes, 
let  stand  overnight,  filter,  wash  with  hot  water,  ignite  and  weigh 
as  BaSO4.  Calculate  to  the  original  basis. 

NOTE. — In  case  the  complete  analysis  is  not  desired,  determine  BaSO4 
as  above  using  1  gram  of  the  dry  material  from  the  moisture  determination; 
then  wash  the  residue  from  the  fusion  with  hot  water  into  a  beaker  and  treat 
the  filter  paper  with  warm  dil.  HC1,  collecting  this  in  the  same  beaker.  The 
whole  precipitate  should  dissolve  completely  in  HC1.  Dilute  this  solution  to 
about  350  cc.,  boil  gently  to  expel  the  CO2  and  add  a  slight  excess  of  dil. 
H2SO4,  drop  by  drop;  let  stand  overnight.  Filter  out  the  BaSO4,  ignite  and 
weigh  as  usual. 

These  two  determinations  give  the  total  SO3  as  BaSO4  and  the  total  Ba 
as  BaSCh;  and  in  a  pure  blanc  fixe  they  should  check  closely.  An  excess  of 
total  Ba  indicates  soluble  barium  salts  [in  the  absence  of  Ba;(PO4)2]  and 
an  excess  of  total  SO3  indicates  other  sulfates. 

Barium  Phosphate. — Boil  2  grams  of  the  original  material  with 
150  cc.  of  water,  filter  and  wash  by  decantation;  return  the  residue 
to  the  original  beaker  and  boil  with  100  cc.  of  water  and  5  cc.  of 
cone.  HNOs.  Filter  and  wash  with  hot  water.  To  the  warm 
filtrate  add  an  excess  of  ammonium  molybdate  solution.  Let 
stand  until  the  precipitate  settles  clear,  then  filter  and  wash 
with  a  2%  HNOa  solution.  Dissolve  the  yellow  precipitate  from 
the  filter  paper  with  dilute  NELiOH.  The  total  volume  should 
be  between  50  and  100  cc.  Add  25  cc.  of  magnesia  mixture,  stir 


312  TECHNICAL  METHODS  OF  ANALYSIS 

well  and  let  stand  1  hour.     Filter  on  a  weighed  Gooch  crucible 
and   wash   with    5%    NHjOH.     Ignite   strongly   and    weigh   as 
Mg2P2O7.     Calculate  to  P2O5  and  to  Ba3(P04)2. 
CALCULATIONS.— Mg2P2O7  X  0.6379  =  P205. 

P2O5X4.2384        =  Ba3(P04)2. 

Mg2P2O7  X  2.7038  =  Ba3  (P04)2. 

General  Calculations. — If  the  material  contains  carbonates 
and  phosphates,  the  acid-soluble  Ba  may  be  present  in  both  forms 
and  the  amounts  can  be  calculated  from  the  total  acid-soluble 
Ba  and  from  the  P2C>5,  figuring  the  latter  to  Ba3(PO4)2  as  above 
described  and  then  the  excess  of  Ba  to  BaC03. 

If  neither  phosphate  nor  carbonate  is  present,  the  soluble  Ba 
is  probably  in  the  form  of  chloride  or  sulfide.  The  Pb  should  be 
calculated  to  PbSO4.  The  Fe  and  Al  may  be  present  as  sulfates 
but  are  generally  reported  as  oxides. 

CALCULATION.— Ba3(PO4)2  X  1.1630  =  BaS04. 
BaSO4X  0.8456      =BaCO3. 

REFERENCE. — This  method  is  based  on  that  described  by  A.  B.  Hutchins 
of  the  Ansco  Co.,  Research  Laboratory,  published  in  Paper,  20,  No.  13,  page 
11  (1917),  somewhat  modified  by  experience  in  this  laboratory. 

BLEACH  (BLEACHING  POWDER) 

Available  Chlorine. — Mix  the  whole  sample  quickly  and  thor- 
oughly, discarding  the  outside  (top  layer)  which  has  lost  more  or 
less  chlorine.  Weigh  out  from  a  weighing  bottle  about  10  grams 
into  a  porcelain  mortar,  add  a  little  water  and  rub  the  mixture  to 
a  smooth  cream.  Then  stir  in  more  water  with  the  pestle,  let 
settle  for  a  few  moments  and  pour  off  through  a  funnel  into  a  liter 
flask.  Again  rub  up  the  sediment  with  water  and  pour  off  as 
before.  Repeat  the  operation  until  the  whole  of  the  material 
has  been  conveyed  into  the  flask  without  loss  and  the  mortar 
washed  clean.  Then  fill  the  flask  to  the  mark  with  water,  mix 
well  and  pipette  out  immediately,  without  allowing  the  material 
to  settle,  50  cc.  into  a  beaker.  Add  50  cc.  of  0.1  N  arsenious  acid. 
Stir  the  mixture  well  and  then  titrate  back  the  excess  of  arsenious 
acid  with  0. 1  N  iodine,  adding  a  little  starch  indicator.  Duplicate 
determinations  should  always  be  made.  From  the  amount  of 
As203  consumed  calculate  the  available  Cl  in  the  bleach. 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS      313 

CALCULATION.— 1  cc.  0.1  N  As2O3  =  0.003546  gram  Cl. 

NOTES. — (1)  It  is  generally  specified  that  a  good  bleaching  powder  should 
contain  not  less  than  35%  of  available  chlorine. 

(2)  A  good  bleach  when  mixed  with  water  in  the  proportion  of  6  parts  of 
bleach  to  94  of  water  and  stirred  thoroughly  for  about  twenty  minutes,  should 
settle  clear  in  not  more  than  an  hour. 

(3)  Bunsen's  method  for  bleaching  powder  is  as  follows:   Pipette  25  cc.  of 
the  bleach  solution  prepared  as  above  described  into  a  beaker  and  add  an  excess 
of  a  10%  solution  of  KI.     Dilute  to  about  100  cc.,  acidify  with  dil.  HC1  and 
titrate  the  liberated  iodine  with  0.1  N  thiosulfate,  adding  a  little  starch  toward 
the  end.     The  titration  gives  the  amount  of  available  chlorine  directly.  This 
method,  however,  is  not  accurate  where  calcium  chlorate  is  present,  since  it 
liberates  the  chlorine  in  the  latter  which  is  of  no  value  in  bleaching.     If  the 
amount  of  chlorate  is  desired,  the  difference  in  chlorine  obtained  by  the  two 
methods  represents  the  chlorine  due  to  chlorate. 

REFERENCE. — Sutton:  "  Handbook  of  Volumetric  Analysis,"  10th  edition, 
page  177. 


BLEACH  CONSUMPTION  OF  PULP 

Weigh  accurately  5  grams  of  the  pulp,  which  should  be  in  the 
air-dry  condition.  Cut  into  pieces  about  an  inch  square  and  place 
in  a  suitable  container,  such  as  a  granite-ware  cup,  together  with 
sufficient  cold  water.  Thoroughly  disintegrate  the  pulp  by  means 
of  an  egg  beater,  taking  care  not  to  lose  any  by  spattering.  The 
disintegration  should  not  take  more  than  five  minutes,  and  should 
be  thorough,  or  there  will  be  lumps  in  the  test  sheets  subsequently 
made. 

Transfer  the  pulp  to  a  funnel  containing  a  perforated  porcelain 
plate,  re-running  the  first  portions  passing  through,  which  usually 
contain  a  little  fiber.  Remove  excess  water  with  suction.  Trans- 
fer the  pulp  to  a  we'ghed  6-ounce  bottle  and  add  about  25  cc.  of 
distilled  water.  Then  add  the  requisite  number  of  cc.  of  stand- 
ardized bleach  solution  from  a  burette.  (See  Note  (1)  below.) 
Place  the  bottle  on  the  scales  and  add  sufficient  distilled  water 
to  make  the  ratio  of  air-dry  pulp  to  water  1  :  20.  In  other  words, 
the  weight  of  the  contents  of  the  bottle  should  be  105  grams,  which 
includes  pulp,  bleach  and  water.  Stir  the  contents  thoroughly 
with  a  glass  rod,  stopper  the  bottle  and  place  in  a  water  bath 
maintained  at  40°  C.  Let  it  remain  for  four  hours,  stirring  fre- 
quently. Remove  the  bottle,  and  filter  the  contents  through  the 


314  TECHNICAL  METHODS  OF  ANALYSIS 

funnel  and  porcelain  plate  originally  used.  Refilter  the  first 
runnings  if  necessary.  Wash  several  times,  using  suction,  and 
test  the  contents  of  the  filter  flask  for  bleach  by  the  addition  of  a 
crystal  of  KI.  If  no  yellow  color  develops,  the  bleach  was  com- 
pletely consumed.  If  a  color  shows,  add  acetic  acid,  and  titrate 
the  liberated  iodine  with  0.1  N  thiosulfate,  using  starch.  The 
solution  should,  of  course,  be  cool.  The  back  titration,  if  any, 
expressed  in  percent  of  bleaching  powder  should  be  subtracted 
from  the  bleach  originally  added.  Transfer  the  bleached  pulp  to  a 
crock  or  small  pan,  add  a  small  quantity  of  water,  stir  well,  and 
make  up  hand  sheets  on  a  brass  wire  mould.  Compare  these 
sheets  and  ascertain  the  least  amount  of  bleach  required  to  pro- 
duce a  good  white. 

The  strength  of  the  original  bleach  liquor  is  determined  as 
follows:  Pipette  off  1  cc.  direct  (or  an  aliquot  representing  1  cc.) 
with  a  standardized  pipette  into  a  flask  containing  about  50  cc. 
of  water  and  a  few  crystals  of  KI.  Acidify  strongly  with  acetic 
acid  and  titrate  the  liberated  iodine  with  0.1  N  thiosulfate.  The 
addition  of  starch  is  unnecessary.  The  end  point  can  be  deter- 
mined by  the  disappearance  of  the  yellow  color. 

1  cc.  0.1  N  thiosulfate  =  0.00355  gram  chlorine.  Assuming 
bleaching  powder  to  contain  33.3%  of  active  chlorine, 

1  cc.  0.1  N  thiosulfate  =  0.0 1065  gram  bleaching  powder. 
Express  results  as  per  cent  of  bleaching  powder  consumed  by  the 
air-dry  pulp. 

NOTES. — (1)  It  is  highly  desirable  that  2,  or  better  3,  parallel  tests  should 
be  carried  out  simultaneously  on  the  same  pulp.  Graduated  amounts  of  bleach 
should  be  used,  say  10%,  15%,  and  20%.  If  preferred,  a  single  test  of  say 
20%  of  bleach  may  first  be  run;  and,  depending  upon  the  result  obtained,  2  or 
more  may  be  subsequently  run,  to  determine  more  definitely  the  bleach  required 
to  produce  a  good  white. 

(2)  It  is  essential  that  the  pulp  density  or  ratio  of  pulp  to  water  be  always 
constant.     It  should  be  emphasized  that  results  are  without  value  unless  all 
conditions  be  maintained  strictly  uniform. 

(3)  Care  should  be  taken  in  the  making  of  the  test  sheets  that  they  be 
made  as  nearly  the  same  thickness  as  possible.     It  is  extremely  difficult  to 
compare  test  sheets  for  color  unless  the  pressure  used  in  drying  (i.e.,  the 
surface),  density,  thickness,  and  in  fact  all  conditions  be  carefully  regulated. 

(4)  The  assumption  of  33^%  active  chlorine  in  bleaching  powder  is  pos- 
sibly slightly  low.     It  is  customary,  however,  to  take  this  first  figure  in  all  our 
experimental  bleaching  operations  because  the  amount  of  chlorine  extracted 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       315 

from  bleaching  powder  in  ordinary  practice  is  in  all  cases  less  than  the  total 
available  chlorine  in  the  dry  powder.  With  35%  available  chlorine  in  the  dry 
powder,  about  33  £%  would  be  actually  present  in  the  pulp  mixture. 

(5)  The  above  method  is  the  result  of  experimental  work  done  in  this 
laboratory  by  R.  B.  Roe. 


CASEIN 

General. — Always  note  the  appearance  and  odor  of  the  sample. 
A  good  casein  should  have  a  clean,  pleasant  odor  and  should  be 
neither  moldy,  musty  nor  rancid.  The  color  should  be  light 
yellow  or  cream  color  and  there  should  be  no  dafk  brown  portions 
or  black  specks.  Bright  orange  particles  indicate  that  the  casein 
has  been  burned  in  drying. 

Moisture. — Weigh  5  grams  into  a  shallow  porcelain  dish  and 
dry  to  constant  weight  at  100-105°  C.  The  temperature  should 
not  be  allowed  to  run  over  105°  C. 

NOTE. — The  moisture  is  not  usually  determined  in  casein.  On  ground 
caseins,  however,  the  maximum  allowable  moisture  is  generally  considered 

12%. 

Ash. — Weigh  5  grams  into  a  porcelain  dish  and  ignite  until  the 
ash  is  white  or  grayish  white  (casein  must  not  be  ashed  in  platinum 
since  it  attacks  this  metal).  Cool  in  a  desiccator  and  weigh. 

NOTE. — The  ash  of  naturally  soured  caseins  generally  runs  between  5  and 
8.5%,  the  ash  of  acid  casein  not  over  6%.  Natural  caseins  burn  to  a  white 
ash  with  greater  ease  than  acid  caseins. 

Alkali. — Add  about  5  cc.  of  distilled  water  to  the  ash  and  warm. 
Then  add  1  or  2  drops  of  phenolphthalein  indicator.  If  the  ash 
is  alkaline,  titrate  it  with  0.1  N  HC1  until  colorless,  then  add  two 
drops  of  methyl  orange  and  complete  the  titration  to  a  pink  color. 
Calculate  to  Na2O. 

CALCULATION.— 1  cc.  0.1  N  HC1  =  0.0031  gram  Na2O. 

NOTE. — The  ash  of  a  pure  casein  should  not  be  alkaline  to  phenolphthalein 
or  to  methyl  orange.  If  it  shows  alkalinity,  test  it  qualitatively  for  borax, 
sodium  carbonate  and  sodium  phosphate. 

Starch  (Qualitative  Test). — Warm  a  portion  of  the  sample 
with  distilled  water.  Cool,  and  add  a  few  drops  of  very  dilute 
iodine  solution.  A  blue  color  indicates  starch. 


316  TECHNICAL  METHODS  OF  ANALYSIS 

NOTE. — If  added  alkali  has  been  found  in  the  casein,  make  the  solution 
slightly  acid  before  adding  the  iodine  solution. 

Solubility  ("  Cutting  Test  ")•— Weigh  out  50  grams  of  the 
ground  casein  into  a  350  cc.  beaker  and  add  7.5  grams  of  powdered 
borax  (equivalent  to  15  per  cent  of  the  weight  of  the  casein).  Add 
250  cc.  of  water  at  a  temperature  of  70°  C.,  and  heat  for  fifteen 
minutes  at  this  temperature  on  the  water  bath,  stirring  constantly. 
High-grade  caseins  will  dissolve  completely.  Inferior  samples 
will  show  more  or  less  lumps  and  mineral  impurities.  If  the  lumps 
are  brown  or  orange  color,  the  casein  has  probably  been  burned  in 
preparation.  Gsit  and  dirt  will  settle  to  the  bottom  and  the 
approximate  amount  should  be  noted. 

In  carrying  out  this  test  always  run  at  the  same  time  a  standard 
high-grade  casein  for  comparison.  The  "  Muriatic  Flakeless  " 
casein  of  Innis  Speiden  &  Co.  is  a  satisfactory  standard.  Italian 
casein  is  also  generally  a  high-grade  casein  but  gives  a  thinner 
solution  than  domestic.  Solutions  of  acid  casein  are  usually  more 
viscous  than  those  of  natural  caseins,  muriatic  caseins  being 
specially  viscous.  Most  of  the  foreign  caseins  give  thinner  solu- 
tions than  domestic  caseins. 

Clay-carrying  Capacity. — Dilute  the  casein  solution  obtained 
above  with  250  cc.  of  hot  water.  10  cc.  of  this  solution  will  then 
contain  1  gram  of  casein.  Keep  the  solution  hot  during  use. 
Weigh  out  100  grams  of  bone-dry  clay  (standard  D.  Y.  coating 
clay,  which  has  been  dried  at  105°  C.,  is  a  suitable  clay  for  this  use) 
and  mix  thoroughly  with  65  cc.  of  water  in  a  small  sauce  pan  or 
casserole.  When  the  mixture  is  perfectly  smooth  and  free  from 
lumps,  add  50  cc.  of  the  casein  solution.  This  is  equivalent  to 
5%  of  casein  on  the  dry  weight  of  the  clay.  Stir  until  smooth. 
Using  a  paint  brush  about  j  inch  wide,  remove  a  brush-full  of 
the  mixture  and  spread  it  evenly  on  one  end  of  a  strip  of  paper 
which  should  be  about  2  feet  long  and  from  7-9  inches  wide.  A 
smooth-surfaced,  fairly  heavy  wrapping  paper  is  suitable. 

Add  10  cc.  more  of  the  casein  solution  to  the  clay  and  mix 
thoroughly.  This  will  make  a  mixture  containing  6%  of  casein 
on  the  weight  of  the  clay.  Stir  this  mixture  until  smooth  and 
brush  on  the  paper  as  before.  Continue  in  this  manner  until 
mixtures  have  been  made  and  applied  to  the  paper  which  contain 
5,  6,  7,  8,  9,  10,  11,  12,  13,  and  14%  of  casein,  respectively,  on  the 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       317 

basis  of  the  weight  of  the  clay.  Let  the  coated  paper  dry  over 
night  at  room  temperature,  or  for  about  three  hours  at  130°  F. 
(55°  C.)«  When  dry,  determine  the  "  critical  clay-carrying  point  " 
in  the  following  manner: 

Soften  a  piece  of  sealing  wax  by  heating  until  it  can  be  easily 
worked  with  the  fingers  for  a  distance  of  0.5  inch  up  the  stick. 
A  convenient  method  of  accomplishing  this  is  to  hold  the  stick  of 
sealing  wax  about  0.5  inch  above  an  electric  hot  plate  until  soft 
and  then  let  it  cool  for  about  fifteen  seconds.  When  this  condi- 
tion is  attained,  hold  the  sealing  wax  0.5  inch  above  the  hot 
plate  for  fifteen  seconds,  remove  it  and  press  it  down  for  an  instant 
on  the  strip  of  clay-casein  coating  which  contains  5%  of  casein. 
Then  pull  up  sharply  and  observe  whether  the  coating  alone  comes 
off  or  whether  some  fiber  from  the  sheet  adheres  to  it.  Heat  the 
wax  as  before  for  fifteen  seconds,  press  down  on  the  strip  of  coating 
which  contains  6%  of  casein  and  pull  up  as  before.  Repeat  until 
that  coating  is  reached  which  adheres  strongly  enough  to  the 
paper  so  that  some  fibers  pull  away  from  the  sheet  when  the  wax 
is  pulled  up.  This  is  the  "  critical  clay-carrying  point."  Repeat 
in  the  same  manner,  starting  from  the  14%  casein  coating  and  run- 
ning down  in  the  opposite  direction,  in  order  to  check  the  critical 
point.  If  they  do  not  check,  the  operation  should  be  repeated. 
Report  the  clay-carrying  capacity  as  the  number  of  parts  of  clay 
which  one  part  of  casein  will  carry.  This  is  obtained  by  dividing 
100  by  the  percentage  of  casein  (on  the  basis  of  the  clay)  in  the 
coating  where  the  critical  point  is  found.  For  example:  If  the 
critical  point  is  found  in  the  coating  containing  9%  casein  on  the 
basis  of  the  clay,  the  clay-carrying  capacity  is  100-5-9  =  11.1. 

NOTES. — (1)  Always  carry  out  parallel  tests  on  a  standard  sample  of  casein 
for  comparison. 

(2)  The  clay-carrying  capacity  of  a  high-grade  casein  is  about  11. 

Acidity. — Weigh  20  grams  of  casein  into  a  casserole,  and  add 
80  cc.  of  water.  Warm,  and  titrate  with  0.5  N  KOH,  running  in  a 
little  at  a  time  with  alternate  warming  on  the  steam  bath  until 
the  end  point  is  reached.  Use  strips  of  litmus  paper  as  an  outside 
indicator  and  apply  a  drop  at  a  time  of  the  casein  solution  to  the 
blue  paper  until  the  red  color  is  faint.  Then  apply  to  both  blue 
and  red  paper  until  the  end  point  is  reached.  Report  the  results 


318  TECHNICAL  METHODS  OF  ANALYSIS 

in  terms  of  cc.  of  normal  caustic  solution  required  to  neutralize 
1  gram  of  casein. 

NOTE. — (1)  This  last  determination  is  not  usually  required. 
(2)  The  tests  for  solubility  and  clay-carrying  capacity  are  of  especial 
value  in  testing  casein  for  use  in  coating  paper. 

CLAY— FOR  PAPER  FILLER 

General. — Clay  or  kaolin  for  use  as  a  filler  in  high  grade  papers 
should  be  pure  white  and  free  from  artificial  bluing.  It  should  not 
have  an  appreciably  gritty  feel  when  rubbed  between  the  teeth. 
The  best  clays  will  not  show  more  than  1-2%  residue  by  the 
flotation  test  nor  more  than  a  few  tenths  of  1%  grit  (generally  less 
than  0.25%)  by  the  200-mesh  sieve  test.  They  should  not  contain 
an  excessive  amount  of  free  moisture  when  shipped. 

Moisture. — Dry  10  grams  to  constant  weight  at  100-105°  C. 
The  loss  in  weight  is  considered  moisture. 

Grit. — (A)  FLOTATION  TEST. — Measure  a  depth  of  2  inches 
from  the  bottom  of  a  500  cc.  beaker  and  make  a  mark  on  the  beaker 
to  indicate  this  height.  Weigh  20  grams  of  the  clay  into  this 
beaker,  mix  thoroughly  with  water  and  fill  up  to  the  mark.  Let 
settle  for  exactly  one  minute  and  pour  off  the  milky  water.  Repeat 
the  process  until  the  supernatant  water  can  be  poured  off  prac- 
tically clear  at  the  end  of  a  minute.  Place  the  beaker  on  the  steam 
bath  until  perfectly  dry,  brush  out  the  settled  grit  into  a  bal- 
anced watch-glass  with  a  camel's  hair  brush  and  weigh  it. 

(B)  200-MESH  SIEVE  TEST. — Place  10  grams  of  the  clay  in  a 
200-mesh  sieve  and  wash  by  means  of  a  slow  stream  of  running 
water  and  finally  with  a  wash  bottle  until  all  the  clay  has  been 
washed  through  the  sieve.  The  residue  which  does  not  pass 
through  is  then  washed  into  a  small  beaker  and,  after  evaporating 
off  the  water  on  the  steam  bath,  is  brushed  into  a  balanced  watch- 
glass  and  weighed. 

NOTE. — In  both  grit  tests  it  is  permissible  and  necessary  to  break  up  any 
lumps  of  clay  with  a  rubber  "  policeman,"  but  no  hard  object  should  be  used 
for  this  purpose  which  might  crush  particles  of  the  grit. 

Color. — Spread  out  a  small  amount  of  the  clay  (preferably 
dried  at  100°  C.)  on  white  paper  by  the  side  of,  and  in  contact  with, 
a  similar  amount  of  a  standard  sample.  Each  should  be  pressed 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS        319 

down  with  a  spatula  to  give  a  smooth  surface.  The  color  is  then 
compared.  When  the  clays  are  of  the  same  color  it  is  impossible 
to  see  any  line  of  demarcation  between  them.  If  a  permanent 
record  is  desired,  the  color  should  be  measured  by  a  colorimeter 
or  tintometer. 

Artificial  Coloring. — In  one  of  two  similar  white  porcelain 
dishes  place  a  measured  amount  of  freshly  prepared,  saturated 
lime  water  and  in  the  other  dish  an  equal  amount  of  clear,  dis- 
tilled or  spring  water.  Then  into  each  of  these  liquids  dust,  from 
the  end  of  a  knife  or  spatula,  a  little  at  a  time,  equal  amounts  of 
clay.  If  the  clay  has  been  artificially  blued,  the  lime  water  will 
remove  the  bluing.  After  letting  stand  for  a  few  moments  the 
excess  liquid  should  be  siphoned  off  and  the  moist  clay  examined. 
If  the  clay  has  been  blued,  the  residue  from  the  lime  water  treat- 
ment will  show  the  original  color,  which  will  be  quite  different 
from  the  color  shown  by  the  moist  clay  treated  with  water  alone 
in  the  other  dish. 

NOTE. — The  so-called  "  turpentine  test  "  for  the  presence  of  artificial 
bluing  in  clay  is  unreliable,  since  certain  natural  clays  when  tested  with 
turpentine  behave  similarly  to  those  which  have  been  artificially  blued. 

CROWN  FILLER 

General. — Crown  filler,  used  as  a  loading  material  or  paper 
filler,  is  a  special  form  of  hydrated  calcium  sulfate. 

Total  Moisture. — Ignite  about  10  grams  over  a  Tirrill  burner 
for  thirty  minutes.  The  loss  in  weight  is  considered  the  total 
moisture  in  the  sample. 

Combined  Moisture. — Calculate  the  amount  of  water  which 
will  combine  with  the  residue  of  anhydrous  CaSCU,  as  found 
above,  to  form  the  crystallized  form,  CaSCX  •  2H2O,  by  multiplying 
the  weight  of  residue  by  the  factor  0.2646. 

Mechanical  Moisture. — Subtract  the  combined  moisture  from 
the  total  moisture  to  obtain  the  free  or  mechanical  moisture. 

NOTE. — This  same  procedure  may  also  be  applied  to  Gypsum  or  Terra 
Alba. 


320  TECHNICAL  METHODS  OF  ANALYSIS 


GLUE 

Moisture. — Weigh  2-3  grams  of  the  glue  into  a  platinum  dish, 
add  -10-15  cc.  of  hot  water,  mix  thoroughly  with  a  small  stirring 
rod  and  rinse  the  rod  off  into  the  dish  with  a  wash  bottle.  Evap- 
orate on  the  steam  bath  to  dryness  and  then  dry  to  constant 
weight  at  105°  C.  The  loss  in  weight  of  the  original  glue  repre- 
sents the  moisture.  A  good  glue  contains  not  less  than  8%  nor 
more  than  16%  of  moisture.  Low  moisture  indicates  over- 
heating in  the  manufacture. 

Ash. — Ignite  the  above  residue  in  the  platinum  dish.  Use  a 
low  heat  at  first,  as  too  rapid  burning  will  make  it  very  difficult  to 
get  rid  of  the  last  of  the  carbon.  Then  raise  the  heat  and  ignite 
to  constant  weight  at  the  full  heat  of  a  Tirrill  burner.  Report 
the  residue  as  ash. 

In  making  the  ash  determination,  note  whether  the  ash  has 
fused  or  not.  The  ash  of  bone  glue  fuses  and  the  aqueous  solution 
is  neutral,  containing  phosphates  and  chlorides.  The  ash  of 
hide  glues  does  not  fuse  owing  to  traces  of  lime  which  render  the 
aqueous  solution  slightly  alkaline.  This  solution  is  also  free  from 
phosphates  or  chlorides.  The  ash  will  vary  from  2-8%,  according 
to  the  quality  of  the  glue.  The  ash  may  also  show  the  presence  of 
alum,  which  is  sometimes  added  to  impart  a  fictitious  "  body  "  to 
glues. 

Acidity  or  Alkalinity. — Dissolve  1  gram  of  the  glue  in  500  cc. 
of  distilled  water.  Add  a  few  drops  of  phenolphthalein  indicator 
and,  if  alkaline,  titrate  with  0.5  N  acid.  Calculate  to  Na2O. 

CALCULATION. — 1  cc.  0.5  N  acid  =  0.01550  gram  Na2O. 

In  case  the  glue  is  acid  instead  of  alkaline,  titrate  the  total 
acidity  with  0.1  N  NaOH  and  phenolphthalein.  It  is  also  often 
necessary  to  make  a  separate  determination  of  the  volatile  and 
organic  acids  in  addition  to  titrating  the  total  acidity.  For  this 
determination  suspend  in  a  stoppered  flask  50  grams  of  the  sample 
with  80  cc.  of  cold  distilled  water  for  about  ten  hours  (or  over- 
night) .  Distill  off  the  volatile  acids  by  means  of  steam  and  collect 
the  distillate  in  a  500  cc.  graduated  cylinder.  After  about  100  cc. 
have  distilled  add  a  few  drops  of  phenolphthalein.  If  the  distillate 
is  found  to  be  alkaline  it  is  not  necessary  to  proceed  further  with 


WOOD,  PAPER  AND  PAPER-MAKING  MATERIALS       321 

the  distillation.  Otherwise,  when  300  cc.  have  come  over,  stop 
the  distillation  and  titrate  the  distillate  with  0.1  N  NaOH  and 
phenolphthalein.  This  volatile  acidity  represents  HC1  and  H2SOs 
and  should  not  exceed  0.2%  for  a  good  glue.  Report  as  "  volatile 
acidity,  calculated  as  sulfurous  acid,  H^SOs." 

Subtract  from  the  original  titration  of  the  glue  the  titration 
required  for  the  volatile  acids  and  calculate  the  difference  as 
H2SO4.  Report  as  "  non-volatile  acids  calculated  as  sulfuric 
acid,  H2SO4." 

CALCULATIONS.— 1  cc.  of  0.1  N  NaOH  =  0.0041  gram  H2SO3. 
1  cc.  of  0.1  N  NaOH  =  0.0049  gram  H2SO4. 

Active  Sulfur. — When  glue  is  to  be  used  for  sizing  anti-tarnish 
papers,  it  is  desirable  to  know  the  amount  of  active  sulfur  present, 
i.e.,  sulfur  in  the  form  of  sulfides  or  sulfites.  The  determination 
of  this  is  conducted  in  exactly  the  same  way  as  the  determination 
of  the  volatile  acidity  above  described,  with  the  exception  that 
5  cc.  of  syrupy  HsPO4  should  be  added  to  the  glue  solution  just 
before  distilling  with  steam  and  the  distillate  should  be  collected 
in  Br  water.  After  distillation,  boil  off  the  Br  from  the  distillate, 
make  acid  with  a  slight  amount  of  HC1  and  precipitate  at  boiling 
temperature  with  BaCl2  solution.  Filter,  ignite  and  weigh  the 
BaSO4  and  calculate  to  SO2.  Report  the  results  as  "  active 
sulfur,  calculated  as  sulfur  dioxide." 

CALCULATION.— BaS04  X  0.274  =  S02. 

Jelly  Test. — A  very  good  idea  of  the  value  of  a  single  glue 
sample,  or  the  comparative  values  of  different  samples,  may  be 
gained  by  testing  the  stiffness  of  the  jellies  formed.  The  jellies 
from  the  unknown  glues  are  compared  with  jellies  from  the  stand- 
ard varieties  of  glues  as  made  by  the  Peter  Cooper  Glue  Factory.* 
The  following  grades  should  be  used  as  standards:  No.  1,  No. 
1-X,  No.  11,  No.  If,  No.  1J,  No.  If,  No.  If,  and  No.  2.  The 
No.  1  is  a  very  high  grade  glue  and  No.  2  a  cheap  glue.  (The 
Cooper  factory  also  puts  out  two  higher  grades  than  No.  1, 
namely,  No.  1  extra  and  A  extra.  Certain  other  manufacturers 
also  claim  to  make  a  glue  even  superior  to  A  extra.) 

The  following  will  give  an  idea  of  the  relative  values  of  the 
glues  as  purchased  in  large  quantities: 

*  Main  works  at  Gowanda,  New  York. 


322 


TECHNICAL  METHODS  OF  ANALYSIS 


1912 

Jan.  1920 

Cents  per  Pound 

Cents  per  Pound 

No.  H 

About  14 

30-35 

No.  If 

About  12 

24-28 

No.  1| 

8-9 

22-25 

No.  2 

6-7 

18-21 

The  method  to  be  used  in  the  jelly  strength  test  is  as  follows: 
First,  decide  as  to  whether  the  unknown  sample  is  probably 
a  low-grade  or  a  high-grade  glue  and  then  select  several  Cooper 
standards  that  will  include  the  grade  of  the  unknown  sample. 
Weigh  out  50  grams  of  each  sample  of  air-dried  glue,  place  in  a 
300  cc.  beaker  and  add  200  cc.  of  cold  water.  Let  the  glues 
soak  in  the  cold  water  until  soft  throughout.  In  the  case  of  a 
ground  glue  this  will  require  not  over  one  hour.  In  the  case  of 
sheet  glues,  several  hours  will  be  necessary.  When  thoroughly 
soaked,  transfer  all  the  samples  at  the  same  time  to  a  steam  bath 
which  has  been  previously  regulated.  Let  the  mixtures  heat  to 
160°  F.  and  hold  at  this  temperature  until  thoroughly  dissolved, 
stirring  them  from  time  to  time  to  prevent  a  skin  forming  on  the 
top.  All  the  samples  should  be  cooked  the  same  length  of  time. 
Fit  a  6-inch  funnel  with  cheese  cloth  and  filter  the  glue  solutions 
into  jelly  glasses  to  within  0.5  inch  of  the  top.  Set  aside  to  cool, 
taking  care  that  the  samples  are  not  disturbed  during  jellying. 
In  hot  weather  it  is  generally  necessary  to  set  the  glasses  in  a  pan 
of  water  to  cool  them;  otherwise  the  jellies  will  not  be  stiff  enough 
for  satisfactory  tests.  This  procedure  may  also  be  used  when 
results  are  desired  quickly.  It  is  most  convenient  to  cook  the 
samples  late  in  the  afternoon  and  allow  them  to  set  overnight. 

The  glasses  containing  the  unknown  and  standard  samples  are 
placed  in  a  row  so  that  the  labels  cannot  be  seen.  Using  the 
third  ringer  of  the  left  hand,  compare  the  jellies  for  firmness  or 
strength  and  rearrange  the  glasses  until  the  jellies  finally  stand  in 
order  of  their  firmness.  Then  examine  the  labels.  The  standard 
samples  should,  of  course,  have  been  arranged  in  correct  order  in 
reference  to  each  other.  From  the  way  the  unknown  samples  are 
distributed  among  the  standard  samples  they  can  be  rated  as  to 


WOOD,  PAPER  AND  PAPER-MAKING  MATERIALS      323 

quality.  (The  grades  of  glue  ordinarily  met  with  in  paper  mill 
work  are  those  from  No.  1 J  to  No.  If.) 

Report  as  "  Peter  Cooper  standard,  No " 

Viscosity. — Dissolve  50  grams  of  the  glue  in  200  cc.  oi  water 
by  means  of  heat.  Determine  the  number  of  seconds  which  is 
required  for  a  100  cc.  Dudley  pipette  to  deliver  its  volume  of 
water  at  approximately  180°  F.  Heat  the  water  to  about  190° 
and  fill  the  pipette  somewhat  above  the  mark.  Have  a  rubber 
tube  with  a  pinch  cock  on  top  of  the  pipette  and  by  means  of  the 
pinch  cock  set  the  water  at  the  mark.  Then  with  a  stop  watch  in 
the  left  hand  open  the  pinch  cock  suddenly  and  at  the  same  time, 
start  the  stop  watch.  Note  the  length  of  time  required  for  the 
water  to  run  from  the  upper  to  the  lower  mark.  Repeat  the 
operation  2  or  3  times  and  take  the  average.  The  opening  of 
the  pipette  should  be  so  adjusted  that  it  will  deliver  100  cc.  of 
water  in  approximately  35  seconds. 

Determine  the  viscosity  of  the  glue  solution  in  the  same  way, 
i.e.,  heat  the  solution  slightly  above  180°  F.;  fill  the  pipette; 
set  it  carefully  on  the  mark  and  determine  the  length  of  time  it 
requires  for  the  glue  solution  to  run  from  the  upper  to  the  lower 
mark.  Run  at  least  2  determinations  and  take  the  average,  if  they 
agree  reasonably  well.  Divide  this  time  by  the  time  required  for 
water  and  report  the  result  as  the  specific  viscosity  of  the  glue 
solution  at  180°  F. 

Grease.— Make  a  strong  water  solution  of  aniline  blue.  Use 
25%  solutions  of  the  different  samples  of  glue  to  be  tested.  To 
25  cc.  of  the  glue  solution  add  2  cc.  of  the  dye,  and  with  a  1.5  inch 
flat  cameFs-hair  brush  draw  a  smooth  streak  of  the  dyed  glue 
across  wrapping  paper.  White  spots  indicate  grease.  A  com- 
parison of  the  white  spots  will  indicate  the  relative  amount  of 
grease  in  the  different  samples. 

The  grease  may  be  determined  quantitatively  by  extracting 
5-10  grams  of  the  ground  and  dried  material  with  anhydrous 
ether  in  a  Soxhlet  extractor,  evaporating  the  ether  and  weighing 
the  residue. 


324  TECHNICAL  METHODS  OF  ANALYSIS 


LIME 

General. — There  are  two  general  classes  of  lime:  (1)  quicklime 
and  (2)  hydrated  lime. 

(1)  QUICKLIME. — Of  this  there  are  two  grades:    (A)   selected 
lime,  which  should  be  well  burnt  lime  picked  free  from  ashes,  core 
clinker,  or  other  foreign  material;  (B)  run-of-kiln,  which  should  be 
well  burnt  lime  but  is  taken  without  selection.     Quicklime  is 
generally  shipped  in  two  forms:    (1)  lump  lime,  the  size  coming 
from  the  kiln,  and  (2)  pulverized  lime,  which  is  lump  lime  reduced 
to  pass  a  0.25  inch  screen. 

Chemically,  quicklimes  are  divided  into  four  types: 

1.  High  Calcium  Lime  (over  90%  CaO). 

2.  Calcium  Lime  (85-90%  CaO). 

3.  Magnesia  Lime  (10-25%  MgO). 

4.  Dolomitic  Lime  (not  under  25%  MgO). 

The  Am.  Soc.  for  Testing  Materials  specifications  require  that 
selected  quicklime  shall  contain  not  under  90%  CaO  and  not 
over  3%  C02)  run-of-kiln  quicklime  shall  contain  not  under  85% 
CaO+MgO  and  not  over  5%  CO2. 

(2)  HYDRATED  LIME. — Hydrated  limes  are  divided  chemically 
into  the  same  four  types  as  the  quicklimes.    It  is  important  in  draw- 
ing the  sample  for  testing  that  it  should  be  taken  from  the  surface 
to  the  center  of  the  package  and  at  least  3%  of  the  packages  should 
be  sampled.    The  sample  should  be  stored  in  an  air-tight  con- 
tainer. 

The  Am.  Soc.  for  Testing  Materials  specifications  demand  that 
the  non-volatile  portion  of  hydrated  lime  shall  contain  not  under 
92%  CaO + MgO,  and  hydrated  lime  shall  contain  not  over  5% 
CO2  and  sufficient  water  to  fully  hydrate  the  CaO  present.  A 
pat  test  is  further  specified  as  follows: 

Pat  Test. — A  3-inch  pat  0.5  inch  thick  in  the  center,  tapering 
to  a  thin  edge,  shall  be  made  on  a  clean  glass  plate  from  a  paste 
composed  of  equal  parts  by  weight  of  hydrated  lime  and  volume- 
constant  Portland  cement  with  only  sufficient  water  to  make  the 
mixture  workable.  This  pat,  after  hardening  twenty-four  hours 
in  moist  air,  shall,  when  exposed  in  a  convenient  manner  to 
steam  above  boiling  water  in  a  loosely  closed  vessel  for  five  hours, 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS      325 

show  no  signs  of  popping,  checking,  cracking,  warping  or  disinte- 
grating. 

Loss  on  Ignition. — Ignite  1  gram  of  the  powdered  lime  in  a 
platinum  crucible,  gently  at  first,  and  then  over  the  blast  lamp, 
until  the  weight  is  constant.  The  loss  in  weight  is  moisture  and 
CO2  and  is  expressed  as  "  Loss  on  Ignition." 

Insoluble  Matter. — Transfer  the  ignited  lime  to  a  beaker  and 
pour  over  it  50  cc.  of  water  and  enough  dil.  HC1  to  dissolve  the 
sample.  Boil  for  five  minutes,  filter,  wash  with  hot  water,  ignite 
and  weigh. 

Iron  and  Aluminum  Oxides. — To  the  filtrate  add  5  cc.  of  cone. 
HC1  and  then  NELtOH  in  very  slight  excess.  Keep  the  solution 
near  the  boiling  point  until  the  odor  of  NHs  is  barely  perceptible. 
Filter  off  the  iron  and  aluminum  hydroxides  while  hot,  collecting 
the  filtrate  in  a  250  cc.  graduated  flask.  Wash  with  hot  water, 
dry,  ignite  in  a  platinum  crucible,  blast,  cool  in  a  desiccator  and 
weigh  as  Al2O3+Fe2O3. 

Lime. — Make  the  filtrate  from  the  preceding  determination 
up  to  250  cc.  Mix  thoroughly  and  pipette  out  100  cc.  into  a  350 
cc.  beaker,  heat  to  boiling  and  add  slowly  a  boiling  solution  of 
3  grams  of  (NH4)2C2O4  in  water.  Continue  the  boiling  two  or 
three  minutes  and  let  the  precipitated  CaC2C>4  settle  for  one-half 
hour.  In  the  case  of  magnesia  limes,  decant  through  a  filter, 
redissolve  the  CaC204  in  the  beaker  and  from  the  filter  with  HC1, 
washing  the  filter  5  times  and  finally  washing  NH^OH  solution 
through  it.  Dilute  the  solution  to  250  cc.,  bring  to  boiling,  add 
1  cc.  of  (NEU) 20264  solution  and  NKtOH  in  slight  excess.  Boil 
for  two  or  three  minutes  and  set  aside  for  one-half  hour.  Filter 
off  the  CaC204  on  the  filter  first  used,  wash  with  hot  water  and 
ignite  in  a  platinum  crucible  over  a  Tirrill  burner,  and  finally  over 
a  blast  lamp  to  constant  weight.  Cool  in  a  desiccator  and  weigh 
as  CaO.  Divide  this  weight  by  0.4  and  multiply  by  100  to  obtain 
the  percentage  of  lime  (CaO)  in  the  original .  sample.  Since 
CaO  absorbs  moisture  from  the  air,  it  should  be  weighed  as  rapidly 
as  possible. 

If  the  lime  contains  only  a  small  amount  of  MgO,  one  precip- 
itation is  sufficient. 

NOTES. — (1)  If  it  is  desired  to  complete  the  analysis  in  as  short  a  time 
as  possible,  a  portion  of  50  cc.  of  the  filtrate  from  the  Iron  and  Aluminum 


326  TECHNICAL  METHODS  OF  ANALYSIS 

Oxides  determination  should  be  precipitated  in  the  usual  way  with  excess  of 
(NH4)2C2O4.  Boil  for  about  five  minutes  and  let  the  CaC2O4  settle  clear. 
Decant  through  a  qualitative  filter  and  cool  (with  ice  water  if  possible) .  Add 
ammonium  phosphate  in  large  excess  and  5-10  cc.  of  cone.  NH.OH.  Stir 
rapidly  with  a  rubber  "p°n'cernan."  From  the  amount  of  precipitate  thus 
formed  one  can  judge  whether  the  lime  contains  sufficient  magnesia  to  require  a 
double  precipitation  or  not.  For  accurate  work,  if  there  is  more  than  a  slight 
amount  of  magnesia,  a  double  precipitation  should  be  carried  out,  using  a  fresh 
100  cc.  aliquot. 

(2)  It  is  allowable  and  sometimes  preferable  to  titrate  the  CaC2O4 
instead  of  igniting  it.  Take  a  portion  of  the  filtrate  from  the  iron  and  alumina 
determination  corresponding  to  0.2-0.25  gram  of  the  material  and  precipitate 
the  CaC2O4  as  above  described.  In  a  400  cc.  beaker  place  about  125  cc.  of 
distilled  water  and  add  5-7  cc.  of  cone.  H2SOi.  Drop  into  this  the  moist  filter 
paper  containing  the  CaC2O4  and  heat  to  about  70°  C.  Stir  to  effect  decom- 
position but  avoid  excessive  disintegration  of  the  paper.  Titrate  the  solu- 
tion with  constant  stirring  with  0.1  N  KMnO4  until  a  permanent  pink  color 
forms.  Calculate  to  CaO. 

CALCULATION.— 1  cc.  0.1  N  KMnO4  =  0.002804  gram  CaO. 

Magnesia. — Acidify  the  filtrate  from  the  CaC2C>4  precipitate 
(or  the  combined  filtrates,  in  case  of  a  magnesia  lime)  with  HC1 
and  evaporate  until  the  salts  begin  to  crystallize.  Dilute  until  the 
salts  are  again  in  solution.  Add  a  volume  of  dil.  NIL^OH  equal  to 
one-third  the  volume  of  the  solution.  Chill  the  solution  and  add 
slowly  and  with  constant  stirring  2  grams  of  Na2HPO4  or 
(NH4)2HPO4  dissolved  in  10  cc.  of  water.  Let  stand  until  com- 
pletely precipitated.  Four  hours  are  usually  sufficient,  but  if 
possible,  it  is  best  to  let  the  solution  stand  overnight.  If  the 
analysis  is  urgent,  stir  for  one-half  hour  and  the  precipitation  will 
be  complete.  Filter  through  a  weighed  Gooch  crucible  (pre- 
viously ignited)  and  wash  with  a  mixture  of  1  part  NEUOH 
(sp.  gr.  0.96),  1  part  alcohol  and  3  parts  water.  Dry  at  105°  C. 
in  the  oven.  Ignite  slowly  and  finally  at  the  highest  heat  of  the 
Tirrill  burner  until  the  weight  is  constant,  cool  in  desiccator 
and  weigh  as  Mg2P2O?. 

CALCULATION.— Mg2P207  X  0.3621  =  MgO. 

Divide  the  weight  of  MgO  by  0.4  and  multiply  by  100  to  obtain 
the  percentage  of  MgO  in  the  original  sample. 

NOTES. — (1)  The  sample  weighed  out  for  analysis  should  be  finely  ground 
and  representative  of  the  whole  sample. 

(2)  The  amounts  of  (NH4)2C2O4  (3  grams)  and  sodium  or  ammonium  phos- 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       327 

phate  (2  grams)  as  given  in  the  procedure  are  ample  to  insure  complete  pre- 
cipitation of  the  lime  and  magnesia. 

(3)  The  residue  insoluble  in  acid  may  contain  some  calcium  and  magnesium 
combined  with  the  silica,  but  for  all  commercial  purposes  it  is  sufficient  to 
report  it  as  "  Insoluble  Matter." 

LIMESTONE 

•  General. — Since  limes  are  made  from  limestones  by  burning 
off  the  C02,  the  analyses  of  the  two  are  in  general  quite  similar. 
For  the  determination  of  Loss  on  Ignition,  Insoluble  Matter,  Iron 
and  Aluminum  Oxides,  Lime,  and  Magnesia,  follow  the  same 
procedures  as  given  above  in  the  method  for  Lime. 

Final  Calculations. — Calculate  the  MgO  and  the  CaO  also  to 
carbonates  and  include  these  figures  in  the  final  report. 

MgOx2.0915  =  MgCO3. 
CaO  X  1.7849  =  CaC03. 

NOTES. — (1)  If  it  is  desired  to  determine  CO2  directly,  this  may  be  done  in 
an  alkalimeter  as  described  under  White  Lead  on  page  212.  For  very 
accurate  results,  however,  the  CO2  should  be  set  free  with  acid  and 
absorbed  and  weighed  in  potash  bulbs  or  soda  lime  tubes. 

(2)  In  case  phosphorus  is  desired,  dissolve  10  grams  in  dil.  HNOs  and 
determine  the  phosphorus  by  the  molybdate  method  as  described  on  page  529. 

ROSIN 

General. — Rosin  is  graded  according  to  color.  The  grades 
are  as  follows:  WW,  WG,  N,  M,  K,  I,  H,  G,  F,  E,  D  and  B. 
The  WW  is  the  best  and  palest  grade.  B  is  the  cheapest  and 
darkest  grade.  Grades  G,  F,  and  E  are  most  frequently  used  for 
paper  making.  Yaryan  Extract  Rosin  grades  between  E  and  F  and 
is  ruby  red  in  color. 

Grade. — To  determine  the  grade  of  rosin  a  set  of  standard 
cubes  of  rosin  of  the  various  grades  must  be  available.  The  rosin 
under  test  is  cast  into  a  cube  in  a  mold  of  sheet  aluminum  and 
compared  as  to  color  with  the  standards  by  looking  through  the 
cubes  toward  the  light.  Care  must  be  taken  to  heat  the  rosin 
only  just  enough  to  pour,  since  overheating  darkens  the  color. 

Dirt  and  Foreign  Matter. — Unless  the  rosin  is  quite  dirty,  no 
quantitative  estimation  is  necessary.  In  case  a  quantitative 


328  TECHNICAL  METHODS  OF  ANALYSIS 

estimation  is  desired,  dissolve  25  grams  of  rosin  in  warm  alcohol; 
filter  through  a  tared  filter  paper;  wash  with  alcohol,  dry  and 
weigh  the  residue. 

Saponification  Number. — Weigh  2  grams  of  powdered  rosin 
into  an  Erlenmeyer  flask  of  300  cc.  capacity.  Add  25  cc.  of  0.5  N 
alcoholic  KOH  and  boil  for  2  hours  under  a  reflux  condenser. 
Shake  the  flask  frequently  with  a  swirling  motion  to  prevent  the 
rosin  from  sticking  to  the  sides  of  the  flask  above  the  liquor  line. 
Cool  and  titrate  the  excess  KOH  with  0.5  N  acid  and  phenol- 
phthalein.  Calculate  the  milligrams  of  KOH  consumed  per 
gram  of  rosin.  This  is  the  saponification  number.  In  each  case 
run  a  blank  on  the  KOH  solution  by  boiling  25  cc.  of  the  solution 
for  two  hours  and  titrating  in  exactly  the  same  manner  that  the 
saponification  proper  is  carried  out. 

CALCULATION.— 1  cc.  0.5  N  KOH  =  28.06  mg. 

Acid  Number. — Dissolve  1  gram  of  powdered  rosin  in  warm 
alcohol  (neutral  to  phenolphthalein) ;  cool  and  titrate  the  solution 
with  0.5  N  KOH,  using  phenolphthalein.  Express  the  result  as 
milligrams  of  KOH  consumed  per  gram  of  rosin.  This  is  the  acid 
number.  It  is  sometimes  customary  to  report  the  per  cent  of 
acid.  This  should  be  calculated  as  abietic  acid. 

CALCULATION. — 1  cc.  0.5  N  KOH  =  0.1512  gram   abietic  acid. 

Ester  Value. — The  ester  value  is  the  difference  between 
the  saponification  number  and  the  acid  number. 

Unsaponifiable  Matter. — Weigh  about  5  grams  of  rosin  and 
saponify  by  boiling  two  hours  with  excess  of  0.5  N  alcoholic  KOH. 
Evaporate  most  of  the  alcohol,  add  about  100  cc.  of  water  and 
extract  in  a  separatory  funnel  with  acid-free  ether,  exactly  as  in 
the  determination  of  free  rosin  in  rosin  size  (page  329). 

Ash. — The  determination  of  ash  is  seldom  necessary.  It  is 
accomplished  by  igniting  5  grams  in  a  platinum  crucible  to  a 
white  or  light  gray  residue.  Cool  in  a  desiccator  and  weigh. 

Practical  Sizing  Tests  of  Rosin. — It  is  sometimes  desirable  to 
make  a  practical  sizing  test  of  rosin  in  comparison  with  a  rosin 
which  is  regarded  as  standard.  For  this  purpose  a  small  beating 
engine  is  desirable,  although  the  work  can  be  done  by  using  a 
cream  whipper.  25  or  50  grams  (dry  weight)  of  unbleached 
sulfite  pulp  are  thoroughly  disintegrated  in  the  beater  or  cream 
whipper  and  2%  of  rosin  sizing  added  in  the  form  of  a  thin  milk. 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS      329 

After  thorough  mixing,  3%  of  a  standard  alum  is  added  in  solution 
and  thoroughly  mixed.  The  pulp  is  then  thinned,  made  into 
hand  sheets  and  the  dried  sheets  are  tested  for  ink  penetration 
(page  354).  Two  sets  of  sheets  are  made,  one  with  size  made 
from  a  standard  rosin  and  the  other  with  size  made  from  the 
rosin  under  test.  The  size  is  made  by  cooking  a  given  weight  of 
powdered  rosin,  in  a  container  surrounded  by  boiling  water,  for 
four  hours  with  that  Weight  of  soda  ash  (Na2COs)  which  will  yield 
a  size  containing  25%  free  rosin  on  the  dry  basis,  i.e.,  with  suf- 
ficient Na2COs  to  neutralize  75%  of  the  free  acid  in  the  rosin. 
The  water  used  in  making  up  the  size  should  be  sufficient  to  give  a 
finished  thick  size  containing  30%  dry  matter.  The  thick  size  is 
diluted  to  a  milk  by  stirring  with  water  at  70°  F.  before  adding  to 
the  pulp. 

ROSIN  SIZE  AND  ROSIN  SIZE  MILK 

General. — Rosin  size  consists  essentially  of  a  mixture  of 
rosin-sodium  soap  with  free  rosin  and  more  or  less  water.  Thick, 
viscous  sizes  generally  contain  from  25-50%  of  water  and  hard,  dry 
sizes  from  1-10%  of  water.  For  paper  mill  use  they  are  very  much 
diluted  with  water  and  used  in  the  form  of  rosin  size  milk,  which 
may  contain  anywhere  from  80-99%  of  water. 

ROSIN  SIZE 

Free  Rosin. — Weigh  out  approximately  10  grams  of  size  and 
mix  with  30  cc.  of  water.  (With  solid  or  dry  size,  6-8  grams  will 
be  sufficient.)  Wash  with  as  little  water  as  possible  into  a  500  cc. 
separatory  funnel,  free  from  any  trace  of  acid  or  alkali.  Extract 
with  25  cc.  of  add-free  ether.  Draw  off  the  watery  layer  into  a 
second  separatory  funnel,  extract  this  with  a  second  portion 
of  add-free  ether  and  add  the  ether  extract  to  that  in  the  first 
funnel.  Wash  the  combined  ether  extracts  with  two  25  cc. 
portions  of  water,  adding  the  wash  waters  to  the  solution  in  the 
other  funnel.  Pour  the  washed  ether  extract  into  a  weighed 
Soxhlet  flask.  Finally  extract  the  water  solution  a  third  time  with 
25  cc.  of  ether,  first  using  the  ether  to  rinse  out  the  funnel  which 
contained  the  ether  extracts.  Draw  off  the  watery  layer  into 
another  separatory  funnel,  wash  the  third  ether  extract  twice 


330  TECHNICAL  METHODS  OF  ANALYSIS 

with  25  cc.  portions  of  water.  Draw  off  the  water  each  time  into 
the  funnel  containing  the  soap  solution.  Pour  the  washed  ether 
extract  into  the  Soxhlet  flask  containing  the  main  ether  extract. 
Distill  off  the  ether  and  dry  the  flask  at  not  over  105°  C.  to  con- 
stant weight.  Cool  in  a  desiccator  and  weigh  the  free  rosin. 

NOTES. — (1)  It  is  especially  important  that  all  ether  used  in  this  deter- 
mination shall  have  been  specially  prepared  by  washing  once  with  Na2CO3 
solution,  once  with  water  and  then  redistilled,  to  free  it  from  all  acid.  It 
should  be  tested  with  a  moist  piece  of  sensitive  blue  litmus  paper,  which  should 
not  change  color  when  completely  submerged  in  it  for  fifteen  minutes. 

(2)  A  convenient  way  to  distill  off  ether  is  to  connect  the  flask  with  a 
Soxhlet  extractor  and  distill  the  ether  up  into  the  extractor. 

Moisture. — Run  the  residue  from  the  free  rosin  determination 
into  a  250  cc.  graduated  flask  (or  a  500  cc.  flask  if  necessary). 
Dilute  to  the  mark  and  mix  thoroughly.  Pipette  an  aliquot 
equivalent  to  one-tenth  of  this  solution  into  a  weighed  platinum 
dish,  evaporate  to  dryness  on  the  water  bath,  place  in  a  water 
oven  and  dry  at  105°  C.  to  constant  weight.  Two  hours'  drying 
ought  to  be  sufficient.  Divide  this  weight  by  0. 1  of  the  weight  of 
the  sample  taken  and  multiply  by  100.  This  gives  the  per  cent 
of  dry  matter  in  the  size,  exclusive  of  free  rosin.  Add  the  per  cent 
of  free  rosin  as  above  determined,  and  subtract  the  sum  from  100; 
the  difference  will  be  the  per  cent  of  water. 

Total  Alkali. — Ignite  the  residue  from  the  moisture  determina- 
tion until  all  carbonaceous  matter  is  burned  off.  Dry  in  a  desic- 
cator and  weigh.  Dissolve  the  residue  in  a  few  cc.  of  water  and 
titrate  with  0. 1  N  acid  and  methyl  orange.  Calculate  the  titration 
directly  to  Na2CO3.  This  weight  should  check  the  weight  of  ash 
reasonably  closely,  unless  the  size  contains  insoluble  or  other  foreign 
matter.  Calculate  the  titration  also  to  Na2O;  divide  the  weight 
thus  obtained  by  0.1  of  the  original  sample  taken,  and  multiply 
by  100.  This  gives  the  per  cent  of  Na2O  in  the  size. 

CALCULATION. — 1  cc.  0.1  N  acid  =  0.0031  gram  Na20. 

=  0.0053  gramNa2CO3. 

Combined  Rosin. — Pipette  an  aliquot  representing  four-fifths 
of  the  soap  solution  from  the  determination  of  free  rosin  into  a 
separatory  funnel  and  acidify  with  10  cc.  of  dil.  H2SO4  (1  :  5). 
Add  25  cc.  of  ether,  shake  well  and  let  stand  until  the  2  layers 
are  completely  separated.  Draw  off  the  water  solution  into  the 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       331 

second  separately  funnel  and  wash  the  ether  with  two  25  cc.  por- 
tions of  water,  drawing  off  the  water  into  the  second  funnel  and 
pouring  the  ether  extract  into  a  weighed  Soxhlet  flask.  Rinse 
the  first  funnel  with  25  cc.  of  ether  into  the  second  funnel.  Shake 
well  and  draw  off  the  water  layer  into  the  first  funnel.  Wash  as 
above  with  two  25  cc.  portions  of  water.  Repeat  once  more. 
Evaporate  the  ether  from  the  combined  extracts  as  in  the  free 
rosin  determination.  Dry  to  constant  weight  at  not  over  105°  C. 
Divide  the  weight  obtained  by  0.8  of  the  original  weight  of  sample 
taken  and  multiply  by  100  to  obtain  the  per  cent  of  combined 
rosin. 

NOTES. — (1)  The  ether  in  this  case  does  not  need  to  be  specially  purified, 
though  it  should  be  free  from  any  non-volatile  residue. 

(2)  The  combined  rosin  thus  obtained  is  weighed  as  rosin  acids,  whereas 
in  the  combined  state  it  is  actually  present  as  anhydride.  There  are  usually 
slight  losses  in  manipulation  and  it  is  customary  to  report  the  combined 
rosin  as  actually  weighed.  Since  rosin  anhydride  =  rosin  acid  X 0.97,  the  usual 
rosin  analysis  should  add  up  somewhat  over  100%,  depending  upon  the  amount 
of  combined  rosin  present. 

Free  Carbonate. — Weigh  out  10  grams  of  size  and  dissolve  in 
200  cc.  of  add-free  absolute  alcohol.  Let  the  solution  stand  eight 
to  ten  hours,  or  overnight  if  possible,  protected  from  acid  fumes 
and  moisture.  Filter  on  a  weighed  dry  filter  and  wash  thoroughly 
with  absolute  alcohol.  Pour  boiling  water  through  the  filter,  and 
after  cooling,  titrate  the  aqueous  solution  with  0.1  N  acid  and 
methyl  orange.  Calculate  to  Na2CO3. 

CALCULATION.— 1  cc.  0.1  N  acid  =  0.0053  gram  Na2CO3. 

NOTES. — (1)  The  filter  need  not  be  weighed  if  the  insoluble  matter  is  not 
to  be  determined.  (See  below.) 

(2)  The  determination  of  free  alkali  by  this  method  is  subject  to  a  slight 
error  on  account  of  the  solubility  of  Na2COa  in  alcohol.  Tests  made  in  this 
laboratory  show  that  when  0.5  gram  of  anhydrous  Na2CO3  was  allowed  to 
stand  sixteen  hours  in  200  cc.  of  95%  alcohol,  0.0075  gram  went  into  solution. 
In  the  case  of  absolute  alcohol  0.0050  gram  dissolved.  With  10  grams  of 
ordinary  rosin  size  and  200  cc.  of  absolute  alcohol,  the  moisture  in  the  size 
dilutes  the  alcohol  to  about  95%  and  the  solubility  of  Na2CO3  would  cause 
results  about  0.07%  too  high.  Consequently,  this  figure  may  be  used  as  a 
negative  correction  where  greater  accuracy  is  desired. 

Insoluble  Matter. — Any  insoluble  matter  will  be  left  on  the 
weighed  filter  in  the  above  determination  of  free  Na2COs  and  may 


332  TECHNICAL  METHODS  OF  ANALYSIS 

be  dried  and  weighed.     In  order  also  to  determine  whether  this  is 
mineral  matter,  it  may  be  ignited  and  the  mineral  matter  weighed. 

ROSIN  SIZE  MILK 

Specific  Gravity. — Take  the  sp.  gr.  with  a  pycnometer  at  a 
definite  temperature;  and  for  the  various  determinations  pipette 
out  definite  volumes  of  the  sample  at  the  same  temperature. 

Total  Solids.— Pipette  100  cc.  into  a 'weighed  platinum  dish, 
evaporate  to  dryness,  then  dry  to  constant  weight  at  105°  C., 
cool  in  a  desiccator  and  weigh. 

Total  Alkali. — Ignite  the  residue  from  the  moisture  deter- 
mination above  and  titrate  with  0.1  N  or  0.01  N  acid  and  methyl 
orange  (see  Total  Alkali  above,  under  Rosin  Size). 

Total  Free  Rosin. — Pipette  100  cc.  into  a  separatory  funnel 
and  extract  with  50-75  cc.  of  acid-free  ether  without  excessive 
shaking  (see  Free  Rosin  under  Rosin  Size  above) . 

NOTE. — If  difficulty  is  experienced  from  emulsions,  add  5-10  cc.  of  neutral 
grain  alcohol  or  very  cautiously  apply  suction  to  the  top  of  the  separatory 
funnel  by  means  of  a  cork  stopper  with  a  glass  tube  running  through  it. 

Inert  Free  Rosin. — If  the  milk  appears  to  contain  suspended 
rosin  which  settles  on  standing,  boil  300  cc.  for  thirty  minutes, 
filter  on  a  filter  paper  which  has  been  dried  at  100°  C.  and  weighed, 
wash  with  hot  water  and  weigh  the  dried  residue. 

Total  Rosin. — Pipette  50  cc.  of  the  milk  into  a  separatory  fun- 
nel, add  10  cc.  of  very  dilute  H2SO4  (1%),  then  50  cc.  of  ether  and 
proceed  as  under  Combined  Rosin  described  above  under  Rosin 
Size. 

Combined  Rosin. — Subtract  the  total  free  rosin  from  the  total 
rosin  and  report  the  difference  as  combined  rosin. 

SATIN  WHITE 

General. — Satin  White  is  a  paste  composed  of  water,  alum- 
inum hydroxide,  calcium  hydroxide  and  hydrated  calcium  sulfate 
and  is  made  by  adding  milk  of  lime  to  alum  in  solution. 

Aluminum  Hydroxide. — Weigh  out  rapidly  10  grams  of  the 
paste;  dissolve  in  dil.  HC1  and  hot  water.  If  any  insoluble  matter 
remains  after  boiling,  it  should  be  filtered  out,  ignited  and  weighed. 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       333 

Make  the  filtrate  up  to  500  cc.  and  pipette  50  cc.  into  a  beaker. 
Make  slightly  ammoniacal,  heat  to  boiling,  filter  out  the  A1(OH)3, 
wash  thoroughly  with  hot  water,  ignite  over  a  Tirrill  burner  and 
then  in  the  blast  lamp  and  weigh  as  A12O3.  Calculate  this  to 
A1(OH)3. 

CALCULATION.— A12O3  X  1.5284  =  A1(OH)3. 

Total  Lime. — Heat  the  filtrate  from  the  A1(OH)3  determination 
to  boiling  and  add  a  slight  excess  of  (NH4)2C2O4  solution.  Let 
settle,  filter,  wash  with  hot  water,  ignite  in  the  blast  lamp  and 
weigh  as  CaO. 

NOTE. — If  preferred,  the  CaC2O4  precipitate  may  be  titrated  with  0.1  N 
KMnO4  (page  326). 

Total  SO3. — Pipette  50  cc.  of  the  original  solution  into  a  beaker, 
dilute  with  100  cc.  of  water,  and  heat  to  boiling.  Then  add, 
drop  by  drop,  a  slight  excess  of  boiling  BaCl2  solution  and  boil  five 
minutes.  Let  stand  overnight.  Filter  out  the  BaSO4,  wash 
with  hot  water,  ignite  and  weigh  as  usual. 

Calculate  the  BaS04  to  CaSO4-2H20,  subtract  the  CaO 
equivalent  of  this  from  the  total  CaO,  and  calculate  the  remainder 
to  Ca(OH)2. 

CALCULATIONS.— BaS04  X  0.7375  =  CaS04  •  2H2O. 
BaSO4X  0.3430  =  SO3. 
CaSO4  •  2H2O  X  0.3257  =  CaO. 
CaO  X  1.3214     =Ca(OH)2. 
SO3  X  2. 1504      =  CaSO4  -  2H2O. 

Moisture. — It  is  generally  customary  to  take  the  moisture 
"  by  difference."  Add  together  the  insoluble  matter,  A1(OH)3, 
CaSO4-2H20  and  Ca(OH)2,  and  subtract  the  sum  from  100, 
reporting  the  difference  as  moisture. 

NOTES. — (1)  The  moisture  cannot  be  accurately  determined  by  direct 
drying  at  105°  C.  because  the  CaSO4-2H2O  loses  some  of  its  water  of  crystal- 
lization on  heating.  If  desired,  the  total  loss  on  ignition  may  be  determined 
and  the  uncombined  water  calculated  from  this.  For  accurate  results  it  is 
necessary  to  use  the  blast  lamp  to  make  sure  all  the  combined  water  is  driven 
off. 

CALCULATIONS. 

Combined  H2O  from  CaSO4  •  2H2O  =  CaSO4  •  2H2O  X 0.2093. 
Combined  H2O  from  Al (OH) 3  =  Al (OH) 3X 0.3460. 
Combined  H2O  fom  Ca(OH)2  =  Ca(OH)2X0.2432. 


334  TECHNICAL  METHODS  OF  ANALYSIS 

(2)  If  any  CaCOs  is  present,  as  is  sometimes  the  case  when  Satin  White 
is  made  from  "  lime  mud,"  it  is,  of  course,  necessary  to  determine  the  amount 
of  CC>2  present  and  take  this  into  account  in  making  the  calculations. 

C  ALCUL  ATION  .— CO2  X  2 .2743  =  CaCO3 . 


TALC  FOR  PAPER  FILLER 

General. — Pure  talc  is  a  hydrated  magnesium  silicate.  The 
commercial  article,  however,  is  generally  a  double  silicate  of  Mg 
and  Al  in  which  the  Mg  predominates.  It  contains,  as  natural 
impurities,  Fe203,  CaCO3,  and  sand.  The  CaC03  is  due  to  the 
difficulty  in  separating  the  talc  from  the  limestone  in  which  it 
occurs.  For  use  as  a  paper  filler,  talc  should  show  an  analysis 
within  the  following  limits : 

Sp.gr 2.7-2.9 

CaC03 Not  over  4% 

Fe203 Not  over  2%. 

Talcs  containing  up  to  10%  of  CaCO3  are  not  necessarily  adul- 
terated, but  if  they  contain  more  than  4%  can  only  be  used  for 
cheap  packing  paper  and  pasteboard. 

Loss  on  Ignition. — Weigh  1  gram  in  a  platinum  crucible, 
ignite  at  bright  red  heat  to  constant  weight  and  calculate  the  loss 
in  weight.  For  normal  talc  this  is  about  4%. 

Calcium  Carbonate. — Place  1  gram  in  400  cc.  of  distilled  water 
and  add  about  2.5-3  cc.  of  cone.  HC1.  Boil  gently  for  fifteen  to 
twenty  minutes;  filter  and  wash.  To  the  filtrate,  add  10  cc.  of 
cone.  HC1.  Then  make  slightly  ammoniacal,  and  filter  out  any 
alumina  which  may  precipitate.  To  the  filtrate  add  (NH4)2C2O4 
solution  in  excess;  and  after  the  precipitate  has  settled,  filter  it 
out,  ignite  and  weigh  as  CaO.  Calculate  to  CaCOs. 

CALCULATION.— CaO  X  1.7848  =  CaCO3. 

Iron  Oxide. — Weigh  1-2  grams  in  a  large  platinum  crucible, 
add  a  few  drops  of  dil.  H2SO4  and  evaporate  2  or  3  times  with 
10-15  cc.  of  HF.  Then  fuse  the  residue  with  anhydrous  KHS04. 
Dissolve  in  water  and  filter  if  necessary.  Add  sufficient  H2SO4 
to  make  a  5%  solution,  and  run  through  the  Jones'  reductor. 
Cool  and  titrate  immediately  with  0.1  N  KMnO4. 

CALCULATION.— 1  cc.  0.1  N  KMnO4  =  0.008  gram  Fe2O3. 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       335 

Specific  Gravity. — Fill  a  200  cc.  beaker  about  two-thirds  full  of 
xylene  (commercial  xylol).  Bend  a  fine  platinum  or  steel  wire 
around  a  platinum  crucible  in  such  a  way  that  it  may  be  sus- 
pended from  the  hook  above  the  balance  pan.  Weigh  the  crucible 
completely  submerged  in  the  xylene.  From  a  weighing  bottle 
partly  filled  with  the  talc,  and  previously  accurately  weighed, 
pour  into  the  crucible  (which  should  be  about  half  full  of  xylene) 
approximately  1  gram  of  the  talc,  very  slowly  and  carefully,  to 
avoid  loss  through  any  of  the  powder  being  blown  away.  Tap  the 
crucible  gently  to  dislodge  any  air  bubbles.  Again  submerge  and 
weigh  in  xylene.  The  increase  in  weight  represents  the  weight 
of  the  talc  in  xylene.  The  weight  of  talc  is  obtained  by  again 
weighing  the  weighing  bottle.  The  difference  between  the  weight 
of  talc  in  air  and  in  xylene  represents  the  weight  of  xylene  dis- 
placed. Determine  the  sp.  gr.  of  the  xylene  in  the  beaker  imme- 
diately with  the  Westphal  balance.  Calculate  the  result  from  the 
formula : 

Wt.  talc  taken 

Sp.  gr.  of  talc  =  -— — — -X  sp.  gr.  of  xylene. 

Wt.  xylene  displaced 

NOTE. — Talc  is  often  adulterated  with  barytes  and  with  feldspar  and  if  the 
sp.  gr.  of  the  talc  is  above  2.9,  it  indicates  that  the  talc  is  adulterated  with 
some  heavy  material  such  as  these. 

Gypsum. — Boil  2  grams  in  a  beaker  with  25  cc.  of  HC1  (1:4) 
and  filter  into  a  250  cc.  volumetric  flask,  washing  the  residue 
thoroughly  with  hot  water.  Cool  the  filtrate  and  dilute  to 
the  mark.  Test  about  100  cc.  of  this  solution  with  BaCb. 
If  it  gives  an  appreciable  precipitate,  the  amount  should  be  deter- 
mined. For  this  purpose  heat  to  boiling  an  aliquot  of  100  cc.  and 
add  a  boiling  hot  solution  of  10  cc.  of  10%  BaCb  solution  a  drop  at 
a  time.  Boil  for  thirty  minutes,  let  stand  until  clear  and  filter  out 
the  BaSO4.  Ignite  and  weigh.  Calculate  to  gyspum. 

CALCULATION.— BaSO4  X  0.7375  =  CaSO4  •  2H2O. 

NOTE. — The  amount  of  CaO  present  as  gypsum  should  be  subtracted  from 
the  total  CaO  as  previously  determined  before  calculating  to  CaCO3. 

Grit. — A  good  idea  of  the  relative  amount  of  grit  in  two 
samples  can  be  obtained  by  placing  alternately  portions  of  one 
and  then  the  other  on  the  tongue  and  rubbing  the  talc  between  the 
teeth.  Quantitative  estimation  is  carried  out  by  means  of  the 


336  TECHNICAL   METHODS  OF  ANALYSIS 

flotation  test  and  the  200-mesh  sieve  test  as  described  in  the 
method  for  Clay  (page  318). 

REFERENCE. — Paper,  6,  No.  4,  page  13  (1912.) 

ULTRAMARINE 

Strength  of  Color. — Weigh  out  1  gram  of  ultramarine  and  10 
grams  of  barytes  (BaSO4)  in  a  1-ounce  bottle  together  with  some 
small  round  lead  shot  and  agitate  until  a  uniform  mixture  is  ob- 
tained, using  great  care  not  to  get  any  of  the  ultramarine  on  the 
stopper  until  it  is  fairly  well  mixed  with  barytes.  This  can  be 
accomplished  by  giving  the  bottle  a  rotating  motion  at  first.  Then 
take  out  a  little  of  the  mixture  with  a  spatula  and  spread  it  upon  a 
piece  of  white  paper  beside  a  similar  portion  of  the  standard  with 
which  the  comparison  is  made. 

A  series  of  standards  should  be  made  up  in  a  similar  manner, 
mixing  with  10  grams  of  BaSO4  the  following  amounts,  respectively, 
of  standard  ultramarine:  0.70,  0.75,  0.80,  0.85,  0.90,  0.95,  1.00,  1.05 
and  1.10  gram. 

In  reporting  the  results  state  whether  the  sample  is  stronger  or 
weaker  than  the  standard  and  give  the  parts  of  sample  equivalent 
to  /me  part  of  the  standard. 

NOTE. — It  is  important  that  the  same  barytes  should  be  used  for  the 
standard  as  for  the  sample  under  examination  and  it  should  be  dried  before 
weighing. 

Resistance  to  Alum. — Weigh  0.2  gram  of  the  sample  into  a 
test-tube  and  add  10  cc.  of  a  10%  solution  of  alum.*  Shake  for 
about  one  minute,  then  allow  it  to  stand  with  an  occasional  shaking. 
Treat  the  standard  ultramarine  in  a  similar  manner  and  compare 
with  the  sample  under  examination.  Some  ultramarines  are 
decomposed  by  alum,  resulting  in  a  decided  weakening  of  the 
shade. 

NOTE. — In  some  instances,  if  the  ultramarine  is  very  resistant,  it  is  neces- 
sary to  warm  the  solution  very  slightly. 

Shade. — Ultramarine  should  be  tested  for  shade  by  comparing 
the  sample  and  the  standard  undiluted,  since  with  dilution  the 
shade  appears  dull. 

*  Paper-makers'  alum,  A12(SO4)3-18H2O. 


. 

WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS      337 

FIBERS  IN  PAPER 

Quantitative  Estimation. — Tear  small  bits  from  different  por- 
tions of  the  sample,  using  in  all  1  or  2  square  inches.  Tear  these 
pieces  into  smaller  pieces  about  -ft  to  J  inch  square  and  place  in  a 
test-tube  about  one-third  filled  with  1%  NaOH  solution.  Boil 
briskly  for  a  few  moments.  Fill  the  test-tube  with  cold  water 
several  times,  decanting  off  the  liquid  each  time.  Finally  fill  the 
tube  completely  with  water  and  invert  on  the  palm  of  the  hand. 
By  raising  the  edge  of  the  tube  cautiously,  allow  all  the  water 
to  drain  out,  leaving  the  pieces  of  paper  in  the  hand.  Roll  these 
into  a  hard  ball  between  the  thumb  and  finger  and  return  to  the 
test-tube.  Make  sure  that  all  the  NaOH  has  been  washed  out  of 
the  paper  fibers.  Fill  the  tube  about  one-third  full  of  water  and 
shake  vigorously.  This  should  completely  disintegrate  the  fibers, 
making  a  uniform  suspension. 

Remove  a  portion  of  the  suspended  fibers  on  the  end  of  a  micro- 
scope needle  and  blot  off  the  excess  moisture  on  a  clean  filter 
paper,  holding  the  needle  horizontally  and  making  sure  that  the 
point  does  not  remove  any  fibers  from  the  filter  paper.  Place  the 
fibers  on  a  clean  glass  microscope  slide  and  add  two  drops  of  fiber 
stain.*  Pull  the  fibers  apart,  using  two  clean  needles  until  a 
uniform  mixture  is  obtained,  free  from  any  lumps  or  clots  of  fibers. 
Place  a  clean  cover  glass  over  the  fibers  and  press  down  gently 
with  the  needles;  blot  off  the  excess  liquid  with  a  clean  filter 
paper.  The  slide  is  then  ready  for  microscopical  examination. 

For  microscopical  examination  a  magnification  of  about  100 
diameters  is  desirable.  An  18  millimeter  (f  inch)  objective 
and  a  25  millimeter  (1  inch)  eye-piece  is  a  satisfactory  combina- 

*  The  stain  is  made  up  as  follows : 

Solution  A :  20  grams  anhydrous  zinc  chloride, 

10  grams  water. 
Solution  B:  2.1  grams  potassium  iodide  crystals, 

0.1  gram  iodine, 

5.0  grams  water. 

Cool  each  solution  and  mix  slowly,  keeping  cool.  Allow  the  precipitate  to 
settle  overnight  and  pour  off  the  supernatant  liquid,  or  filter  through  glass 
wool.  Add  a  small  flake  of  iodine  and  preserve  the  stain  away  from  the 
light  or  in  a  brown  glass-stoppered  bottle.  The  stain  should  be  allowed  to 
stand  a  day  or  two  before  using. 


i 

338  TECHNICAL  METHODS  OF  ANALYSIS 

tion.  In  general,  the  different  fibers  used  in  paper  are  colored  by 
the  stain  as  follows : 

Rag  (cotton,  linen,  hemp) :  pale  red  to  brownish  or  pur- 
plish red. 

Bleached  chemical  wood  (sulfite>  soda,  etc.):  deep  blue. 

Ground  wood:  bright  yellow,  sometimes  pale  yellow. 

Jute  and  manila:  vary  all  the  way  from  blue  through  violet 
and  red  violet  to  brownish-yellow  and  greenish-yellow. 

Straw  and  esparto:  generally  dark  blue,  but  sometimes  reddish 
or  yellowish. 

For  the  characteristics  of  the  different  fibers  the  standard 
books  should  be  consulted;  particularly  good  illustrations  and 
descriptions  are  given  in  Herzberg's  "  Papier-priifung,"  3d  edition 
(pages  88  and  89,  and  tables  in  the  back  of  the  book). 

In  estimating  the  amounts  of  the  various  constituents,  standard 
slides  *  should  be  prepared  from  papers  of  known  composition 
(page  339),  and  frequently  compared  with  the  samples  under 
examination. 

Qualitative  Test  for  Ground  Wood. — There  are  several  reagents 
which,  when  applied  to  the  surface  of  a  paper,  show  characteristic 
colors  if  ground  wood  is  present.  Such  tests,  however,  are  of 
questionable  value  in  arriving  at  any  estimation  of  the  amount  of 
ground  wood  and  microscopical  examinations  should  always  be 
made.  The  principal  test  solutions  for  the  presence  of  ground 
wood  are  as  follows : 

(1)  Aniline  Sulfate. — Dissolve  5  grams  of  aniline  sulfate   in 
50  cc.  of  distilled  water  and  add  a  drop  of  cone.  H2SO4.     This 
solution  is  not  permanent,  but  decomposes  rather  easily,  taking 
on  a  violet  coloration.     It  should  be  used  only  when  it  is  colorless. 
When  applied  to  paper  containing  ground  wood,  it  gives  a  bright 
yellow  color. 

(2)  Phloroglucinol. — Dissolve  1  gram  of  phloroglucinol  in  50  cc. 
of  alcohol  and  add  about  25  cc.  of  cone.  HC1.     This  gives  a  pale 
yellow  solution   which   keeps  fairly  well   when   protected   from 
air  and  light.     A  fresh  solution  works  more  sharply  and  quickly 
than  an  old  one.     The  color  which  it  gives  on  paper  containing 
ground  wood  is  a  bright  magenta. 

(CAUTION. — Jute,  manila  and  unbleached  sulfite  sometimes 
give  a  pale  pink  coloration.  An  indication  of  traces  of  ground 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       339 

wood   by  this  test   should   therefore   be   confirmed   by  a  micro- 
scopical examination.) 

(3)  Dimethyl-p-phenylenediamine  (Wiirster's  Reagent). — A  water 
solution  of  this  compound,  when  dropped  upon  a  paper  containing 
ground  wood,  gives  an  orange  red  spot  after  a  short  interval. 

(4)  Nitric  Acid. — Cone.  HNOs  when  applied  to  a  paper  con- 
taining ground  wood  gives  a  deep  yellow  color. 

STANDARD  PAPERS  FOR  FIBER  ANALYSIS 

General. — Before  making  up  any  standard  papers,  the  raw 
materials  should  be  tested  to  see  that  they  are  pure  sulfite,  soda, 
rag,  etc. 

Sulfite-Rag  Standards. — Pure  sulfite  pulp  and  unfilled  pure 
rag  paper  should  be  used  for  the  sulfite-rag  standards.  After 
determining  the  moisture  in  each,  weigh  them  out  into  100-gram 
bundles  and  place  in  a  tightly  covered  can.  When  it  is  desired 
to  make  up  a  certain  sulfite-rag  standard,  the  amount  of  bone-dry 
stock  required  should  be  calculated  from  the  moisture  figures, 
the  100-gram  bundles  reweighed,  and  correction  made  for  any 
change  in  moisture  content  which  may  take  place  during  storage. 
The  proper  weight  of  the  stock  having  been  determined,  add  the 
sulfite  to  the  beater  and  partly  cut  down;  then  add  the  rag  paper 
and  beat  the  two  for.  some  time,  with  the  knives  down.  Raise 
the  knives  and  stir  the  contents  of  the  beater  for  one  and  one-half 
to  two  hours.  Make  up  sheets  from  this  stock  on  a  hand  mold, 
press  between  blotters,  and  mark  for  identification. 

Soda-Rag  Standards. — Follow  the  same  procedure  as  for  the 
sulfite-rag  standards,  using,  however,  pure  soda  pulp  in  place  of 
sulfite  pulp. 

Other  Standards. — For  other  standard  papers  follow  the  same 
general  procedure,  taking  special  precaution  to  make  certain  of 
the  purity  of  the  original  raw  materials. 

CHEMICAL  ANALYSIS  OF  PAPER 

General. — The  analyses  described  in  this  method  do  not  include 
fiber  analysis,  which  is  described  of  page  337.  For  the  deter- 
mination of  tarnishing  properties  and  sizing  tests  see  pages  362 
and  355,  respectively. 


340  TECHNICAL   METHODS  OF  ANALYSIS 

Mineral  Matter  (Ash). — Ignite  2  grams  in  a  porcelain  crucible 
until  all  the  carbon  has  been  burned  off,  brush  the  ash  carefully 
into  a  balanced  watch  glass  and  weigh  it.  Since  the  ash  of  paper 
is  generally  very  light,  great  care  must  be  taken  that  none  of  it 
is  blown  out  of  the  crucible  by  drafts  of  air.  For  this  reason 
the  crucible  should  always  be  kept  covered  after  the  main  por- 
tion of  the  organic  matter  has  been  burned  off. 

NOTES. — (1)  If  the  paper  is  filled  with  crown  filler,  multiply  the  ash  as 
actually  determined  fr"  1.265  to  obtain  the  equivalent  of  CaSO4-2H2O  as  it 
existed  in  the  sheet. 

(2)  Unfilled  papers  sometimes  show  a  blue  ash,  due  to  the  presence  of 
ultramarine.  The  amount  of  the  latter  may  be  determined  in  many  cases  by 
carefully  igniting  a  considerably  quantity  of  the  paper  until  all  the  carbon 
has  been  burned  off,  then  taking  a  quantity  of  clay  or  calcium  sulfate  equal 
to  the  weight  of  the  ash  and  determining  how  much  of  a  standard  sample  of 
ultramarine  must  be  mixed  with  this  to  produce  the  depth  of  color  shown  by 
the  ash. 

Filler. — As  a  rule,  the  presence  of  more  than  1%  of  ash  in  a 
white  paper  indicates  that  it  contains  added  filler.  It  should  be 
borne  in  mind,  however,  that  the  ash  will  not  indicate  the  actual 
amount  of  filler  in  the  paper  since  the  filler  always  contains  more 
or  less  moisture  and  volatile  matter  which  is  driven  off  when  the 
paper  is  ashed.  The  nature  of  the  filler  will  be  indicated  by 
qualitative  tests  as  follows : 

Boil  the  ash  with  dil.  HC1,  filter  on  a  quantitative  filter  and 
wash.  Test  a  portion  of  the  filtrate  for  sulfates  by  boiling  with  a 
small  amount  of  BaCl2  solution.  Test  the  remainder  of  the  filtrate 
for  Al  by  adding  an  excess  of  NHiOH.  Then  filter  and  test  the 
filtrate  for  Ca  by  adding  (NHi)  20264.  The  presence  of  any 
considerable  amount  of  Ca  and  of  sulfate  at  this  point  indicates 
that  the  paper  is  filled  with  crown  filler,  CaSO4-2H2O;  whereas 
only  a  small  amount  of  Ca  would  probably  be  due  to  lime  in  clay 
or  other  insoluble  filler. 

Transfer  the  residue  insoluble  in  HC1  to  a  platinum  crucible, 
burn  off  the  filter  paper,  and  then  fuse  with  Na2COs  to  a  clear 
fusion.  Treat  the  fusion  with  hot  water  until  it  can  be  removed 
from  the  crucible.  Dissolve  a  small  portion  of  the  residue  insoluble 
in  hot  water  in  dilute  HC1 ;  if  it  gives  a  clear  solution,  this  indicates 
the  absence  of  BaSO4.  In  this  case  dissolve  the  entire  fusion  in 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       341 

HC1  and  evaporate  to  dryness.  Take  uj)  with  warm,  dilute  HC1 
and  filter.  The  insoluble  residue  will  be  SiCV 

In  case  the  original  fusion  does  not  dissolve  in  HC1,  boil  it 
with  water,  filter  and  wash  thoroughly  Dissolve  the  residue 
insoluble  in  hot  water  in  dilute  HC1  and  add  dilute  H2S04.  A 
white  precipitate  shows  the  presence  of  Ba.  Acidify  a  portion 
of  the  water  solution  with  HC1  and  add  BaCb  solution.  A  white 
precipitate  shows  the  presence  of  sulfates. 

To  the  bulk  of  the  HC1  solution  of  the  fusion,  or  to  the  bulk 
of  the  water  solution  (after  adding  an  excess  of  HC1  and  boiling) 
add  a  slight  excess  of  NHiOH  and  boil.  A  white  gelatinous 
precipitate  shows  Al.  Filter,  and  to  the  filtrate  add  an  excess  of 
(NHi)  20264  solution.  A  white  precipitate  shows  the  presence 
of  Ca.  Filter,  and  acidify  the  filtrate  with  HC1  and  evaporate 
to  the  point  of  crystallization.  Cool,  and  add  an  excess  of  ammo- 
nium phosphate  solution.  Stir  thoroughly.  A  white  crystalline 
precipitate  shows  the  presence  of  Mg. 

INTERPRETATION  OF  RESULTS. — A  considerable  amount  of  CaO 
and  SO3  soluble  in  HC1  indicates  crown  filler,  CaSO4-2H2O.  The 
presence  of  Ba  and  of  SOs  in  the  insoluble  residue  indicates  blanc 
fixe,  BaS04.  The  presence  of  Ba  soluble  in  HC1  with  effervescence 
indicates  BaCOs.  An  alkaline  ash  showing  lime  soluble  in  HC1, 
but  not  showing  SOs,  indicates  CaCOs  (whiting  or  chalk).  Con- 
siderable amounts  of  silica  and  alumina,  with  or  without  small 
amounts  of  Ca  and  Mg,  indicate  china  clay,  but  if  the  amount  of 
Mg  is  considerable  the  filler  is  probably  agalite,  talc  or  asbestine. 
A  microscopical  examination  of  the  ash  will  often  give  a  clue  as  to 
the  nature  of  the  filler.  Agalite  crystallizes  in  needles,  asbestine 
is  fibrous. 

NOTE. — It  is  not  usually  possible  to  distinguish  between  talc  and  clay  con- 
taining a  little  magnesia  without  a  quantitative  determination  of  the  amount 
of  MgO  in  the  ash  of  the  paper.  It  is  sufficiently  accurate  to  treat  the  ash  in 
a  platinum  crucible  with  H2SO4  and  evaporate  once  or  twice  with  HF  to 
remove  SiO2.  Then  take  up  the  residue  in  warm  dil.  HC1  (it  should  practically 
all  dissolve  unless  Ba  salts  are  present),  add  NH4OH,  boil  until  the  odor  of 
NH3  is  nearly  gone  and  then  add,  without  filtering,  a  slight  excess  of 
(NH4)2C2O4.  Filter,  wash  with  hot  water,  add  a  slight  excess  of  HC1  and 
evaporate  till  crystallization  begins.  Dilute  until  the  crystals  just  dissolve 
and  precipitate  the  Mg  as  MgNH4PO4  in  the  usual  way.  Ignite  and  weigh 
as  Mg2P2O7  and  calculate  the  per  cent  of  MgO  in  the  weight  of  paper  ash 


342  TECHNICAL  METHODS  OF  ANALYSIS 

taken.     Clay  rarely  contains  over  a  few  per  cent  of  MgO,  whereas  talc  contains 
approximately  31  per  cent. 

Retention. — The  retention  is  generally  figured  from  the  ash, 
although  for  accurate  results,  the  ash  should  be  corrected  for  the 
natural  moisture  in  the  filler.  The  calculation  of  retention  is  as 
follows : 

Subtract  the  percentage  of  filler  from  100%  to  obtain  the  per- 
centage of  fiber  in  the  sheet;  divide  the  pounds  of  fiber  fur- 
nished by  the  percentage  of  fiber  in  the  paper  to  obtain  the  pounds 
of  paper  made  from  the  engine.  From  this  figure  subtract  the 
pounds  of  fiber  furnished  and  the  balance  is  the  pounds  of  filler 
retained.  This  figure,  divided  by  the  pounds  of  filler  furnished, 
gives  the  percentage  of  retention. 

Acidity. — Papers  containing  free  acid  are  rare.  For  practical 
purposes,  however,  the  acidity  due  to  excess  of  alum  is  to  be  con- 
sidered free  acid. 

TOTAL  ACIDITY. — For  purposes  of  comparison,  total  acidity 
may  be  determined  as  follows : 

Warm  5  grams  of  paper  with  250  cc.  of  distilled  water,  pour 
off  the  water  and  titrate  while  still  hot  with  0.1  N  NaOH  and 
phenolphthalein  until  a  permanent  pink  color  is  obtained.  Run 
a  "  blank  "  on  an  equal  amount  of  the  water.  Subtract  the 
"  blank  "  titration  from  the  other  titration  and  calculate  the 
difference  to  80s. 

CALCULATION.— 1  cc.  0.1  N  NaOH  =  0.004  gram  S03. 

SULFUBOUS  ACID. — Tear  up  50  grams  of  the  paper  and  place  in 
a  500  cc.  distilling  flask  with  about  350  cc.  of  distilled  water.  Distill 
until  150  cc.  have  come  over  and  collect  the  distillate  in  a  flask  con- 
taining about  50  cc.  of  water  with  a  few  drops  of  bromine  water 
added  to  it.  Acidify  with  dil.  HC1  and  boil  off  the  Br;  then  add 
a  slight  excess  of  BaCb  solution.  Boil  till  the  precipitate  settles 
clear.  Filter  out  the  BaSO4,  ignite,  and  weigh  in  the  usual  manner. 
From  the  weight  of  BaSC>4,  calculate  the  amount  of  862 . 

CALCULATION.— BaSO4  X  0.2744  =  S02. 

NOTE. — Qualitative  tests  for  the  acidity  of  the  paper  are  generally  suf- 
ficient. A  satisfactory  paper  should  not  give  more  than  a  slight  acid  reaction 
when  pressed  in  contact  with  moistened  blue  litmus  paper  between  sheets 
of  filter  paper  for  fifteen  minutes.  Sulfurous  acid  in  papers  that  have  been 
exposed  to  the  air  for  any  length  of  time  is  oxidized  to  sulfuric  acid. 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       343 

Free  Chlorine. — Free  chlorine  is  seldom  found  in  papers.  If 
present,  it  can  be  detected  by  placing  the  paper  in  a  dilute  solution 
of  KI  made  weakly  acid  with  H2S04,  to  which  has  also  been  added  a 
few  drops  of  starch  solution.  Free  chlorine  in  the  paper  will 
liberate  iodine,  which  will  give  a  blue  color  with  the  starch.  If 
desired,  the  amount  can  be  determined  by  titrating  the  iodine 
with  0. 1  N  thiosulf ate  solution. 

Chlorides. — Free  chlorine  or  hypochlorites  from  excess  of 
bleach  in  the  paper  do  not  remain  as  such  for  any  length  of  time 
but  are  reduced  to  chlorides.  The  presence  of  the  latter,  however, 
in  appreciable  amount  is  also  objectionable.  To  determine  the 
amount  of  chlorides  present,  weigh  5-10  grams  of  the  paper,  tear  it 
up  in  small  bits  and  heat  to  boiling  with  distilled  water  in  a  beaker. 
Pour  off  the  water  and  repeat  the  boiling  with  two  fresh  portions 
of  water.  Filter  the  combined  extracts  if  necessary.  Add  a  few 
drops  of  dil.  HNOa  and  a  slight  excess  of  AgNOs  solution.  Filter 
the  AgCl  on  a  Gooch  crucible.  Wash  with  hot  water,  dry  and 
weigh.  Calculate  to  Cl. 

CALCULATION.— AgCl  X  0.2474  =  Cl. 

NOTE. — If  preferred,  the  solution  may  be  titrated  with  0.1  N  or  0.02 
N  AgNOs,  using  K2CrO4  solution  as  an  indicator.  (See  page  509.) 

COATED  PAPERS 

The  coating  consists  of  a  mineral  substance  or  substances 
with  an  adhesive  binder  to  make  a  coherent  film  upon  the 
surface  of  the  paper.  When  papers  are  properly  coated,  the 
coating  should  not  "  pick "  or  lift  off  when  the  moistened 
thumb  is  pressed  momentarily  against  the  coating  and  then 
withdrawn  with  a  quick  jerk.  In  the  case  of  poorly  coated  papers, 
more  or  less  of  the  coating  will  adhere  to  the  thumb  when  thus 
tested.  Papers  may  be  single  coated  (coated  on  one  side)  or 
double  coated  (coated  on  both  sides). 

Amount  of  Coating. — Weigh  a  piece  of  the  paper  cut  exactly 
2X5  inches  and  place  in  a  flat  glass  dish.  The  dishes  used  for 
developing  in  photography  are  convenient  for  this  purpose. 
Cover  with  water  containing  1%  of  NKiOH  and  set  aside  in. a 
warm  place  (two  or  three  hours  is  generally  sufficient  to  loosen  the 
coating).  Remove  the  paper  to  a  large  watch  glass,  rub  the  sur- 


344  TECHNICAL  METHODS  OF  ANALYSIS 

face  with  a  small  camel's  hair  brush  cut  off  square,  and  wash  the 
coating  into  a  beaker.  If  the  paper  is  double  coated,  turn  it  over 
and  repeat  on  the  other  side.  Continue  the  operation  until  all 
the  coating  is  washed  into  the  beaker.  Dry  the  paper  and  weigh 
it  under  the  same  conditions  as  those  under  which  the  original 
paper  was  weighed.  The  loss  in  weight  is  the  weight  of  coating. 
Calculate  this  to  per  cent  of  the  original  sample  and  also  figure 
the  weight  of  coating  on  the  basis  of  a  ream  of  500  sheets  24X36 
inches  (see  table  on  page  351). 

Analysis  of  Coating. — Heat  the  mixture  in  the  beaker  to 
boiling  and  filter  through  a  qualitative  filter.  Test  the  filtrate 
for  glue,  casein  and  starch.  For  the  qualitative  tests  for  glue 
and  starch,  see  page  355.  Casein  can  generally  be  detected  by 
the  odor  and  also  by  the  fact  that  it  will  precipitate  from  the 
solution  when  carefully  neutralized  with  HC1.  A  confirmatory 
test  for  casein  may  be  made  on  the  original  paper  as  follows : 

Boil  1  or  2  square  inches  of  the  paper  with  5  cc.  of  water 
to  which  is  added  5  drops  of  dil.  H2SO4.  Decant  the  liquid  from 
the  paper  into  a  test  tube,  cool  and  add  1  drop  (not  more)  of  3% 
formaldehyde.  Mix  and  pour  this  solution  gently  down  the  side 
of  an  inclined  test  tube  containing  2  cc.  of  cone.  H2S04  to  which 
has  been  added  1  drop  only  of  10%  FeCls  solution,  taking  care 
that  the  water  solution  flows  on  the  top  of  the  H2SO4  without 
mixing  with  it.  If  casein  is  present,  a  violet  ring  forms  at  the 
junction  of  the  liquids.  Glue  does  not  give  more  than  a  brownish 
color  and  rosin  does  not  react.  A  blank  test  should  be  conducted, 
using  a  small  amount  of  casein,  or  preferably,  a  paper  which  is 
known  to  contain  casein. 

The  usual  substances  to  be  looked  for  in  the  mineral  part  of 
the  coating  are  (1)  blanc  fixe,  BaS04j  (2)  satin  white,  a  mixture 
of  CaSO4-2H2O,  Ca(OH)2  and  A1(OH)3;  (3)  china  clay,  aluminum 
silicate  (approximately  Al2Si2O7  •  H2O) ;  and  (4)  chalk,  CaCOs. 

Wash  the  residue  on  the  filter  paper  into  a  beaker  with  a 
stream  of  water,  first  punching  a  hole  in  the  paper.  Pour  10-15 
cc.  of  hot  dil.  HC1  through  the  filter  into  the  same  beaker.  Heat 
the  solution  to  boiling  (note  whether  the  acid  causes  effervescence 
of  CO2) .  Let  settle,  decant  through  a  quantitative  filter  and  heat 
the  residue  in  the  beaker  with  a  second  portion  of  100  cc.  of  dil. 
HC1.  Filter  through  the  same  filter,  washing  with  hot  water. 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       345 

Divide  the  filtrate  into  two  portions.  Test  one  for  sulfates  with 
BaCU  solution  and  the  other  for  Al  and  Ca.  The  presence  of  Ca, 
Al  and  864  indicates  that  satin  white  was  used  in  the  coating.  If 
Ca  is  found  but  no  S04  and  if  the  coating  gives  an  effervescence 
with  HC1,  it  contains  chalk  or  whiting  (CaCOs).  If  the  coating 
contains  carbonates  but  is  free  from  Ca  (and  Mg),  test  the  HC1 
solution  for  Ba,  as  in  some  special  papers  BaCOs  is  used. 

Ignite  the  filter  containing  the  residue  from  the  HC1  treatment 
above,  and  fuse  with  excess  of  Na2COs  in  a  platinum  crucible. 
Boil  the  fusion  with  water  and  filter,  washing  well  with  hot  water. 
To  the  nitrate  add  HC1  in  excess  and  boil  off  all  CO2.  Test  a 
portion  of  the  solution  for  sulfate  with  BaCb  solution.  Evaporate 
the  remainder  to  dryness,  take  up  with  HC1  and  note  whether 
any  SiCb  is  present.  If  so,  filter  out  and  test  the  filtrate  for  A^Os 
by  boiling  with  an  excess  of  NH^OH.  A  slight  precipitate  here 
may  be  due  to  alum  from  the  paper;  a  heavy  precipitate  indicates 
china  clay,  if  silica  was  also  found  present.  Add  (NH4)2C204 
solution  to  the  filtrate  from  the  alumina,  boil  and  filter  out  any 
CaC2(>4  that  may  precipitate.  Test  this  filtrate  for  Mg,  which  in 
considerable  amount  might  indicate  the  presence  of  talc. 

Dissolve  the  water-insoluble  portion  of  the  fusion  with  HC1. 
Test  a  portion  of  it  for  Ba  with  H2SO4.  If  a  precipitate  is  obtained, 
confirm  this  by  dipping  a  platinum  wire  into  the  remainder  of  the 
HC1  solution  and  holding  it  in  the  flame.  Barium  will  give  a 
green  coloration  to  the  flame.  If  both  Ba  and  sulfate  are  found 
in  the  fusion  of  the  residue  insoluble  in  HC1,  the  coating  contains 
blanc  fixe. 

NOTE. — After  removing  the  coating,  the  uncoated  paper  may  be  tested  for 
ash  and  filler  as  previously  described.  The  test  for  rosin,  if  called  for,  should 
be  made  on  the  original  paper. 

REFERENCES. — Herzberg:  "  Papier-priifung  ";  Griffin  and  Little :  "The 
Chemistry  of  Paper  Making  'J;  U.  S.  Dept.  of  Agriculture,  Report  No.  89, 
by  F.  P.  Veitch. 

PHYSICAL  TESTING  OF  PAPER 

General. — Before  cutting  the  samples  for  the  physical  tests,  it 
is  necessary  to  determine  the  machine  and  cross  directions  of  the 
sheet.  Depending  on  the  individual  papers,  one  of  the  following 
methods  can  be  used : 


346  TECHNICAL  METHODS  OF  ANALYSIS 

(a)  Cut  a  circle  1  or  2  inches  in  diameter  from  the  sheet  and 
moisten  on  one  side.  The  paper  will  curl  about  an  axis  corre- 
sponding to  the  machine  direction  of  the  paper. 

(6)  Cut  a  strip  1  cm.  wide  and  15-20  cm.  long  from  each  direc- 
tion of  the  sheet,  hold  the  ends  together  and  let  the  strips  bend 
of  their  own  weight,  first  to  the  right  and  then  to  the  left.  The 
paper  is  less  flexible  in  the  machine  direction,  hence  when  the 
machine  direction  is  uppermost  there  will  be  an  opening  between 
it  and  the  lower  strip.  When  bent  the  other  way  the  two  strips 
will  lie  together  and  the  cross  direction  strip  will  then  be  on  top. 

(c)  The  direction  can  sometimes  be  told,  especially  on  cylinder- 
made  papers,  by  examining  the  surface  of  the  sheet.     The  fibers 
will  have  a  very  marked  tendency  to  be  drawn  out  along  one 
direction,  namely  the  machine  direction. 

(d)  Certain   papers   tear  straight  in  the  machine   direction 
and  very  unevenly  in  the  opposite  direction. 

Tensile  Strength. — Make  the  determination  on  the  Schopper 
machine  (Fig.  16).  Cut  strips  from  both  directions  of  the  paper 
exactly  15  mm.  wide  and  about  240  mm.  long,  if  it  is  possible  to 
obtain  strips  of  this  length  without  folds.  A  strip  of  this  length 
can  be  used  where  the  jaws  are  180  mm.  apart,  in  which  case 
the  percentage  stretch  can  be  read  directly  from  the  scale.  Cut 
at  least  5  strips  in  each  direction  and  report  the  average  of  the 
5  tests.  If  the  individual  tests  vary  considerably,  run  at  least  10 
in  each  direction.  In  placing  the  strip  in  the  machine,  first  clamp 
it  in  the  lower  jaw,  then  pull  it  through  the  upper  jaw  and  clamp. 
Adjust  the  stretch  device  catch  and  release  the  locks  on  the  upper 
jaw  and  on  the  pendulum  previous  to  starting  the  machine. 
Results  are  obtained  in  kilograms  per  15  mm.  Calculate  to 
pounds  per  inch. 

CALCULATION. — Kg.  per  15  mm.X3.72  =  lbs.  per  inch. 

For  the  calculation  of  breaking  length,  weigh  each  strip  previous 
to  testing  and  also  determine  its  total  length  in  millimeters.     Cal- 
culate as  follows : 
Breaking  length  (yards)  = 

Tensile  Strength  (Kg.  per  15  mm.)Xlength  of  strip  (mm.)  X  1.094 
Wt.  of  strip  (grams) 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS        347 


The  breaking  factor  or  tensile  factor  is  the  tensile  strength 
(pounds  per  inch)  in  each  direction  divided  by  the  weight  in 
pounds  of  a  ream  of  500  sheets,  24X36  inches. 


FIG.  16. — Schopper  Tensile  Machine. 

Stretch  Test. — If  a  180  mm.  strip  is  used  for  testing,  the 
stretch  will  be  given  directly  by  the  machine,  in  percentage.  If  a 
shorter  strip  is  used,  the  percentage  stretch  will  have  to  be  cal- 
culated from  the  actual  stretch  in  millimeters. 

Folding  Tests. — Determine  the  folding  strength  in  double 
folds  on  the  Schopper  folding  machine  (Fig.  17).  Cut  the  strips 


348 


TECHNICAL  METHODS  OF  ANALYSIS 


for  testing  15  mm. 'wide  and  about  J  inch  longer  than  the  strip 
gauge  accompanying  the  folding  machine.  Fasten  the  strip 
in  the  jaws  after  releasing  the  tension  of  the  jaw  heads.  After 
the  strip  is  in  place,  pull  back  the  jaw  heads,  set  the  gauge  at  zero 
and  release  the  lock  on  the  wheel.  The  machine  should  run  at 
120  R.P.M.  Test  at  least  5  strips  in  each  direction.  (Test  10 
if  the  individual  results  vary  widely.) 

The  folding  result  is  affected  by  the  relative  humidity  of  the 
atmosphere.     For    purposes    of    record,  therefore,    the    relative 


FIG.  17. — Schopper  Folding  Machine. 

humidity  and  the  temperature  should  always  be  recorded  at  the 
time  the  tests  are  made  and  it  is  preferable  to  conduct  the  tests 
in  a  room  where  temperature  and  humidity  are  maintained  con- 
stant. 

The  folding  factor  is  the  folding  strength  in  each  direction 
divided  by  the  weight  in  pounds  of  a  ream  of  500  sheets,  24X36 
inches. 

NOTE. — It  is  very  necessary  that  the  small  steel  wheels  which  support 
the  clamping  jaws  be  perfectly  round,  well  oiled  and  revolve  easily  as  the 
jaws  move  back  and  forth,  as  otherwise  results  may  be  seriously  affected. 


WOOD,  PAPER  AND  PAPER-MAKING  MATERIALS         349 


Mullen  Test  (Bursting  Strength)  and  Thickness. — Use  the 

small  Mullen  machine  (Fig.  18)  for  light  weight  papers  and  the 
large  (Jumbo)  machine  for  heavier  weight  papers  and  cardboard. 
Make  at  least  5  tests  and  report  the  average.  The  reading  of  the 
gauge  is  in  pounds  per  square  inch. 

Place  the  sheet  over  the  diaphragm  and  clamp  securely. 
Make  sure  that  the  sheet  is  smooth  and  that  no  wrinkles  or 
creases  occur  within  the  space  to  be  tested.  Set  the  pressure 
gauge  at  zero  and  apply  pressure  by  turning  the  wheel  with  a 


FIG.  18.— Perkins  Mullen  Tester. 

smooth,  rapid  motion  free  from  jerks.  When  the  paper  breaks, 
immediately  reverse  the  wheel  to  remove  pressure  on  .the  dia- 
phragm and  then  take  reading  of  the  gauge. 

Determine  the  thickness  by  a  number  of  tests,  using  a 
thickness  gauge  (Fig.  19),  and  taking  the  test  near  each  Mullen 
break.  Average  the  Mullen  tests  and  thickness  results.  The 
average  Mullen  test,  divided  by  the  thickness  in  ten  thousandths 
of  an  inch,  is  the  strength  ratio,  or  bursting  ratio. 

Example. — Mullen  test  =  20  Ibs.  and  thickness  =  0.0018  inch. 
Then  the  strength  ratio  =  20-5- 18  =  1.11. 

The  average  Mullen  strength  divided  by  the  weight  in  pounds 
of  a  ream  of  500  sheets,  24X36  inches,  is  the  strength  factor  or  the 
bursting  factor. 


350 


TECHNICAL  METHODS  OF  ANALYSIS 


Ream  Weight. — If  a  sufficiently  large  sample  of  the  paper  is 
available,  weigh  a  sheet  of  the  desired  size  on  the  ream  weight 
scales  (Fig.  20),  which  give  directly  the  weight  of  a  ream  of  500 
sheets  or  480  sheets,  as  the  case  may  be.  For  instance,  if  the  ream 
weight  24X36  —  500  is  desired,  one  sheet  24X36  inches  weighed 
on  the  ream  weight  scales  would  give  the  ream  weight  in  pounds 
direct.  In  case  the  size  of  the  sample  is  limited,  cut  a  small  piece 
of  the  paper  to  accurate  measurement  and  weigh  on  a  precision 


FIG.  19. — Thickness  Gauge. 

balance/  and  calculate  the  ream  weight  from  this  weight.  A 
piece  2X5  inches  (i.e.,  10  square  inches  in  area)  is  a  convenient 
size. 

The  standard  ream  for  writing  and  printing  papers  is  500 
sheets  each  24X36  inches,  and  unless  otherwise  specified  the  cal- 
culations should  be  on  this  basis.  If  a  piece  of  10  sq.  in.  is 
employed,  then: 

Wt.  in  grams  X  95. 2  =  ream  weight. 

The  designation  of  the  size  of  the  ream,  etc.,  is  as  follows: 
Ream  weight  24X36  —  500,  50  Ibs.  For  wrapping  papers  the 
ream  is  generally  480  sheets  instead  of  500  sheets, 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       351 

The  following  table  gives  the  "  factors  "  with  their  logarithms 
for  calculating  the  ream  weights,  on  several  different  bases,  from 
the  weight  in  grams  of  a  piece  2X5  inches. 


Size  of  Sheet 

Sheets  in  Ream 

"  Factor  " 

Logarithm 

Inches 

24   X36    '  • 

500 

95.2 

.9786 

24   X36 

480 

91.4 

.9608 

8|X11 

500 

10.31 

.0131 

12|X16 

500 

22.05 

.3433 

121X16 

480 

21.16 

.3255 

14   X17 

500 

26.24 

.4190 

14   X17 

480 

25.19 

.4012 

16   X21 

500 

37.0 

.5686 

16   X21 

480 

34.6 

.5385 

17   X22 

500 

41.2 

.6153 

17   X22 

480 

39.6 

.5975 

17   X26 

500 

48.7 

.6877 

17   X26 

480 

46.8 

.6699 

17   X28 

500 

52.5 

.7199 

17   X28 

480 

50.4 

.7021 

18  X24 

500 

47.6 

.6778 

18   X24 

480 

45.7 

1.6600 

19   X24 

500 

50.3 

1.7013 

19   X24 

480 

48.3 

1.6835 

20  X25 

500 

55.1 

1.7413 

20   X25 

480 

52.9 

1.7235 

24   X38 

500 

100.6 

2.0026 

24  X38 

480 

96.6 

1.9848 

25   X38 

500 

104.7 

2.0199 

25   X38 

480 

100.5 

2.0023 

27   X39 

500 

116.1 

2.0650 

27   X39 

480 

111.5 

2.0472 

34  X46 

500 

172.5 

2.2368 

34  X46 

480 

165.6 

2.2190 

40  X48 

500 

211.7 

2.3257 

40  X48 

480 

203.2 

2.3079 

352  TECHNICAL   METHODS  OF  ANALYSIS 

Substance  Number.— In  October,   1916,  the  Writing  Paper 

Manufacturers  Association  adopted  the  "  Substance  Number  " 
system  for  designating  the  weights  of  paper.  The  folio  size 
(17X22  inches)  is  taken  as  the  basis  and  the  weight  of  a  ream  of 
500  sheets  of  folio  size  is  the  substance  number.  By  specifying 


FIG.  20.— Ream  Weight  Scales  (Fairbanks  Co.). 

the  substance  number,  therefore,  the  weight  of  paper  desired  is 
definitely  established  and  the  weight  per  ream  of  any  other  size, 
or  the  substance  number  of  any  paper,  the  ream  weigh ;  of  which 
is  known  on  some  other  basis,  may  be  readily  ascertained  by 
reference  to  the  following  table : 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       353 

TABLE  SHOWING  ACTUAL  WEIGHTS   (FIGURED  TO  0.5  LB.)   OF    STANDARD 
SUBSTANCE  NUMBERS* 


Size 

Substance 

No.  13 

No.  16 

No.  20 

No.  24 

No.  28 

No.  32 

No.  36 

No.  40 

No.  44 

Inches 
14X17 
14X34 

8.5 
16.5 

10.0 
20.5 

12/5 
25.5 

15.5 
30.5 

18.0 
35.5 

20.5 
40.5 

23.0 
46.0 

25.5 
51.0 

28.0 
56.0 

15X19 

10.0 

12.0 

15.0 

18.5 

21.5 

24.5 

27.5 

30.5 

33.5 

16X21 
16X26 
16X42 

11.5 

14.5 
23.5 

14.5 
18.0 
29.0 
16.0 

18.0 
22.0 
36.0 

21.5 
26.5 
43.0 

25.0 
31.0 
50.5 

28.5 
35  5 
57.5 

32.5 
40.0 
64.5 

36.0 
44.5 
72.0 

39.5 
49.0 
79.0 

17X22f 

13.0 

20.0 

24.0 

28.0 

32.0 

36.0 

40.0 

44.0 

17X26 
17X28 
17X44 
17X56 

15.5 
16.5 
26.0 
33.0 

19.0 
20.5 
32.0 
40.5 

23.5 
25.5 
40.0 
51.0 

28.5 
30.5 
48.0 
61.0 

33.0 
35.5 
56.0 
71.5 

38.0 
40.5 
64.0 
81.5 

42.5 
46.0 
72.0 
91.5 

47.5 
51.0 
80  0 
102.0 

52.0 
56.0 
88.0 
112.0 

18X23 
18X46 

14.5 
29.0 

17.5 
35.5 

22.0 
44.5 

26.5 
53.0 

31.0 
62.0 

35.5 
71.0 

40.0 
79.5 

44.5 

88.5 

'48.5 
97.5 

19X24 
19X26 
19X28 
19X30 
19X48 

16.0 
17.0 
18.5 
20.0 
31.5 

19.5 
21.0 
23.0 
24.5 
39.0 

24.5 
26.5 
28.5 
30.5 
49.0 

29.5 
31.5 
34.0 
36.5 
58.5 

34.0 
37.0 
40.0 
42.5 
68.5 

39.0 
42.5 
45.5 
49.0 
78.0 

44.0 
47.5 
51.0 
55.0 

88.0 

49.0 
53.0 
57.0 
61.0 
97.5 

53.5 
58.0 
62.5 
67.0 
107.5 

20X28 
20X56 

19.5 
39.0 

24.0 
48.0 

30.0 
60.0 

36.0 
72.0 

42.0 
84.0 

48.0 
96.0 

54.0 
108.0 

60.0 
120.0 

66.0 
132.0 

21X32 
21X33 

23.5 
24.0 

29.0 
29.5 

36.0 
37.0 

43.0 
44.5 

50.5 
52.0 

57.5 
59.5 

64.5 
66.5 

72.0 
74.0 

79.0 
81.5 

22X342 

19.5 
26.0 

2i.O 
32.0 

30.0 
40.0 

36.0 
48.0 

42.0 
56.0 

48.0 
64.0 

54.0 
72.0 

60.0 
80.0 

66.0 
88.0 

23X28 
23X31 
23X34 
23X36 

22.5 
25.0 
27.0 
29.0 

27.5 
30.5 
33.5 
35.5 

34.5 
38.0 
42.0 
44.5 

41.5 
45.5 
50.0 
53.0 

48.0 
53.5 
58.5 
62.0 

55.0 
61.0 
67.0 
71.0 

62.0 
68.5 
75.5 
79.5 

69.0 
76.0 
83.5 

88.5 

76.0 
84.0 
92.0 
97.5 

24X38 
24X48 

31.5 
40.0 

39.0 
49.5 

49.0 
61.5 

58.5 
74.0 

68.5 
86.0 

78.0 
98.5 

88.0 
111.0 

97.5 
123.0 

107.5 
135.5 

26X32 
26X33 
26X34 
26X38 

29.0 
30.0 
30.5 
34.5 

35.5 
36.5 
38.0 
42.5 

44.5 
46.0 
47.5 
53.0 

53.5 
55.0 
56.5 
63.5 

62.5 
64.0 
66.0 
74.0 

71.0 
73.5 
75.5 

84.5 

80.0 
82.5 
85.0 
95.0 

89.0 
92.0 
94.5 
105.5 

98.0 
101.0 
104.0 
116.5 

27X40 

37.5 

46.0 

.58.0 

69.5 

81.0 

92,5 

104.0 

115.5 

127.0 

•  28X34 
28X38 
28X40 

33.0 
37.0 
39.0 
41.5 

40.5 
45.5 
48.0 
51.0 

51.0 
57.0 
60.0 
63.5 

61.0 
68.5 
72.0 
76.5 

71.5 
79.5 
84.0 
89.0 

81.5 
91.0 
96.0 
102.0 

91.5 
102.5 
108.0 
114.5 

102.0 
114.0 
120.0 
127.5 

112.0 
125.0 
132.0 
140.0 

30X38 

39.5 

49.0 

61.0 

73.0 

85.5 

97.5. 

109.5 

122.0 

134.0 

31X53 

57.0 

70.5 

88.0 

105.5 

123.0 

140.5 

158.0 

175.5 

193.5 

34X44 

52.0 

64.0 

80.0 

96.0 

112.0 

128.0 

144.0 

160.0 

176.0 

*  Paper,  Dec.  6,  1916,  page  17.          f  Folio  size,  basis  of  standard. 


354  TECHNICAL  METHODS  OF  ANALYSIS 

Penetration  or  Sizing  Tests. — (a)  FOR  WRITING  PAPERS. — 
Float  a  piece  of  paper  1  or  2  inches  square  on  the  surface  of  ink, 
arid  note  the  time  in  minutes  until  the  ink  begins  to  be  visible  on 
the  upper  surface.  The  time  in  minutes  is  taken  as  a  basis  for 
comparing  the  relative  sizing  of  different  papers.  (See  also 
page  358.) 

NOTE. — In  order  to  avoid  discrepancies  due  to  the  variation  in  the  ink, 
the  latter  should  be  made  according  to  the  following  formula  given  by  Schluttig 
and  Neuman  in  "  Die  Eisengallustiten  ": 

Gallotannic  acid .' 23.4  grams 

Gallic  acid 7.7  grams 

Gum  arabic 10.0  grams 

Hydrochloric  acid 2.5  grams* 

Ferrous  sulfate  crystals  (FeSO4-7H,O) 30.0  grams 

Methylene  blue 2.0  grams 

Water  to  make  up  to  1  liter. 

Let  settle  several  days  and  then  decant   from   any  sediment. 

(6)  FOR  PAPERS  OTHER  THAN  WRITING  PAPER. — For  all 
papers  other  than  writing  papers  use  the  so-called  Ferrocyanide 
Test  as  follows : 

Float  a  piece  of  paper  about  2  inches  square  on  the  surface  of 
a  5%  solution  of  KiFe(CN)6  and  note  the  time.  Then  test  the 
upper  surface  of  the  piece  of  paper  from  time  to  time  by  stroking 
(across  the  machine  direction)  with  a  small  camel's  hair  brush 
moistened  with  a  solution  of  FeCls  (5-10%).  When  the  ferro- 
cyanide  has  soaked  up  through  the  paper  sufficiently  to  come  in 
contact  with  the  FeCls,  it  will  react  the  moment  the  latter  is 
applied  and  give  a  blue  color.  The  penetration  is  then  consid- 
ered complete,  the  time  is  again  noted,  and  the  length  of  time 
since  the  paper  was  laid  upon  the  surface  of  the  solution  is  taken 
as  the  measure  of  its  resistance  to  penetration.  In  stroking  the 
paper  with  the  camel's  hair  brush,  take  care  to  select  a  place  on 
the  paper  which  has  not  previously  been  wet  with  the  FeCla 
solution.  Report  the  results  to  the  nearest  minute,  or,  if  the 
time  is  very  short,  in  seconds. 

Blotting  Paper. — The  absorption  test  on  blotting  paper  is 
carried  out  as  follows : 

Cut  strips  of  the  paper,  in  both  directions,  about  0.5  inch 
*  2.5  grams  of  actual  HC1  are  equivalent  to  5.8  cc.  of  cone.  HC1. 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS      355 

wide  and  at  least  3.5  inch  long,  and  make  a  pencil  mark  about 
J  inch  from  one  end.  Then,  starting  from  this  mark,  make  a  series 
of  pencil  marks  at  intervals  of  f  inch  on  the  paper  for  a  distance 
of  about  2.5  inches.  Suspend  the  strips  in  water  in  such  a  manner 
that  the  surface  of  the  water  coincides  with  the  first  mark.  When 
the  strip  is  first  placed  in  the  water,  note  the  time  and  at  the  end 
of  three,  five,  and  ten  minutes,  respectively,  ascertain  the  rise  of 
the  water  in  the  paper  by  means  of  the  marks  upon  it.  Report 
the  result  in  sixteenths  of  an  inch,  i.e.,  a  paper  which  shows  an 
absorption  of  1  inch  will  be  reported  as  "  Absorption,  16."  If 
necessary,  a  small  quantity  of  ink  may  be  added  to  the  water  to 
aid  in  determining  the  exact  rise  of  the  liquid.  Test  several 
strips  of  each  sample  cut  from  each  direction  and  report  the 
average  absorption. 

SIZING  IN  PAPER 

General. — Blotting  paper  and  so-called  "  water-leaf  paper  " 
are  unsized  and  rapidly  absorb  ink  or  any  other  liquid  by  capillary 
attraction.  Papers  which  are  to  be  used  for  writing  or  printing 
purposes  must  be  sized  with  some  material  which  will  prevent 
this  capillary  absorption.  Rosin  and  glue  ("  animal  size ") 
are  most  commonly  used.  Starch  is  also  used  to  some  extent, 
generally  together  with  rosin  and  glue,  particularly  in  the  case  of 
blueprint  papers.  Paper  containing  a  considerable  proportion  of 
rags  sometimes  contains  a  small  amount  of  starch  due  to  its  incom- 
plete removal  from  the  rags. 

It  is  advisable  to  make  qualitative  tests  before  proceeding 
with  quantitative  determinations. 

Qualitative  Tests. — (A)  GLUE. — Boil  several  grams  of  the 
paper  with  water  until  the  volume  of  the  latter  is  only  a  few  cc. 
(as  soon  as  the  water  has  come  to  boiling,  a  portion  of  it  may  be 
poured  off  and  saved  for  the  starch  test).  Filter  and  cool  thor- 
oughly. To  this  add  about  an  equal  volume  of  a  cold  10%  NaCl 
solution  nearly  saturated  with  tannic  acid  and  freshly  filtered. 
A  light  grayish  yellow,  flocculent  precipitate  indicates  the  presence 
of  glue.  (It  should  be  remembered  that  casein  will  also  give  this 
test.) 

NOTES. — (1)  If  the  paper  has  been  treated  with  formaldehyde  in  addition 
to  glue,  the  latter  will  be  rendered  more  or  less  insoluble  in  hot  water.  In  this 


356  TECHNICAL  METHODS  OF  ANALYSIS 

case  boil  the  sample  with  dil.  NaOH  solution,  pour  off  the  solution  and  make 
slightly  acid  with  HC1.  Cool,  and  test  this  solution  with  tannic  acid.  Run  a 
"  blank  "  with  the  NaOH  to  make  sure  that  it  contains  nothing  which  will 
precipitate  tannin  after  acidification. 

(2)  In  case  the  paper  contains  starch  and  gives  a  precipitate  by  the 
above  test,  the  precipitate  may  be  due  to  the  starch.  In  this  case,  repeat 
the  test  and,  before  adding  the  tannic  acid  solution,  add  sufficient  HC1  to  the 
concentrated  water  extract  of  the  paper  to  give  about  a  2%  solution.  Digest 
on  the  steam  bath  until  the  starch  is  all  converted  to  dextrose  and  a  drop  of 
the  solution  gives  no  blue  color  when  added  to  5  cc.  of  very  dilute  (about  0.001 
N)  iodine  solution.  Then  cool  the  solution  and  add  the  tannic  acid-NaCl 
solution. 

(B)  ROSIN     (LIEBERMANN-STORCH    TEST).  —  Place     several 
small  pieces  (representing    about  1-2  grams)  of  the  paper  in  a 
clean  dry  test-tube.     Cover  with  pure  acetic  anhydride  and  boil 
down  to  about   1   cc.     The  fumes  of  anhydride  are  extremely 
irritating  and  after  they  begin  to  come  off  from  the  test-tube  it 
is  well  to  hold  the  mouth  of  the  latter  near  a  flame  so  that  the 
fumes  will  burn  as  fast  as  they  are  driven  off.     Pour  the  liquid 
residue  into  a  clean  dry  test-tube  and  cool  thoroughly.     If  any  waxy 
particles  separate,  they  should  be  filtered  off.     Let  one  drop  of 
cone.  EbSCX  run  carefully  down  the  side  of  the  test-tube.     A 
fugitive  rose  violet  coloration,  formed  when  the  acid  meets  the 
anhydride,  indicates  rosin. 

(C)  STARCH. — Boil  a  portion  of  the  paper  with  water.     Cool 
and  filter  if  necessary.     Add  one  drop  of  very  dilute  iodine  solution 
(about  0.01  N).     A  blue  coloration  indicates  starch.     There  are 
some  papers  not  sized  with  starch  which  will  give  a  faint  violet 
coloration,  but  this  should  be  disregarded. 

NOTE. — Applying  iodine  solution  directly  to  the  paper  may  give  mislead- 
ing results. 

Quantitative  Tests.— (A)  GLUE.— Weigh  3-5  grams  of  the 
paper,  tear  into  small  pieces,  and  place  in  a  500  cc.  Kjeldahl 
digestion  flask.  Determine  the  nitrogen  by  the  Gunning  method 
as  described  on  page  65.  Calculate  to  glue  by  multiplying  the 
nitrogen  found  by  5.6. 

(B)  ROSIN. — Cut  5  grams  of  the  paper  into  strips  approximately 
0.5  inch  wide  and  fold  in  numerous  small  crosswise  folds.  The 
folding  is  essential  to  secure  complete  and  quick  extraction.  Do 
not  tear  the  paper  into  small  pieces,  since  it  will  then  stick  together 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS      357 

and  not  be  completely  extracted.  Place  the  folded  strips  in  a 
Soxhlet  extractor  and  fill  the  latter  with  acidulated  alcohol. 
This  is  made  by  adding  to  100  cc.  of  95%  alcohol  10  cc.  of  acidulated 
water,  consisting  of  3  cc.  of  glacial  acetic  acid  to  100  cc.  of  water, 
and  thoroughly  mixing.  Connect  the  extractor  to  an  unweighed 
Soxhlet  flask;  add  sufficiently  more  of  the  acidulated  alcohol  to 
insure  having  the  flask  about  one-quarter  full.  When  the  extractor 
is  filled,  start  the  extraction  and  syphon  at  least  10  times. 

Wash  the  alcoholic  extract  into  a  beaker  and  evaporate  to 
10  cc.  or  less  on  the  steam  bath.  Cool,  take  up  in  about  25  cc. 
of  ether  and  transfer  to  a  300  cc.  separatory  funnel  containing 
about  150  cc.  of  water,  to  which  has  been  added  a  little  salt  to 
prevent  emulsion.  Shake  thoroughly  and  allow  to  separate. 
Draw  off  the  water  into  a  second  separatory  funnel  and  repeat 
the  treatment  with  a  fresh  25  cc.  portion  of  ether.  Combine  the 
ether  extracts  which  contain  the  rosin  and  wash  twice  with  100  cc. 
portions  of  water  or  until  the  ether  layer  is  perfectly  clear  and  the 
line  between  the  ether  and  the  water  sharp  and  distinct. 

If  glue,  which  is  extracted  from  the  paper  by  the  alcohol, 
should  interfere  by  emulsifying  with  the  ether,  wash  the  com- 
bined ether  extracts  with  a  10-15%  NaCl  solution  (twice  if  nec- 
essary), and  then  wash  with  three  100  cc.  portions  of  distilled 
water  to  remove  the  NaCl. 

Finally  transfer  the  ether  extract  to  a  weighed  flask  and  evap- 
orate off  the  ether.  Dry  at  100°  C.  in  a  water  oven  for  exactly 
one  hour.  Cool  in  a  desiccator  and  weigh. 

(C)  STARCH. — Prepare  from  the  paper  a  solution  containing 
approximately  1%  of  reducing  sugar  (dextrose).*  This  solution 
must  not  contain  over  1%  and  if,  after  the  analysis  is  completed,  it 
is  found  that  this  limit  is  exceeded,  the  analysis  must  be  repeated, 
using  a  sriialler  amount  of  paper.  The  procedure  is  as  follows: 

Weigh  carefully  3-5  grams  of  the  paper,  cut  in  very  small  pieces 
(about  J  inch  square),  into  a  250  cc.  Erlenmeyer  flask;  add  150  cc. 
of  water,  and  boil  for  about  five  minutes.  Cool  to  about  50°  C. 
and  shake  violently  until  the  fibers  are  well  separated.  Then  add 
10  cc.  of  filtered  saliva  solution.  (See  note  (1)  below.)  Place  the 
flask  in  a  water  bath  at  40-50°  C.  and  stir  frequently  for  one  hour; 
then  add  1  drop  of  0.1  N  iodine  solution.  *  If  there  is  no  indication 
*Starch-sized  papers  generally  contain  2%  or  less  of  starch. 


358  TECHNICAL  METHODS  OF  ANALYSIS 

of  starch  being  present  (blue  color) ,  filter  on  a  Gooch  crucible  and 
wash  with  hot  water.  Transfer  the  filtrate,  which  should  have 
a  volume  of  about  200  cc.,  to  a  beaker;  add  15  cc.  of  dil.  HC1 
(5 : 4)  and  boil  gently  for  forty-five  minutes,  covering  the  beaker 
with  a  watch  glass.  Cool  immediately.  Nearly  neutralize  the 
acid  with  NaOH  and  complete  the  neutralization  with  Na2CO3 
and  litmus  paper.  Filter  the  neutral  solution  into  a  250  cc.  flask; 
make  up  to  the  mark,  and  determine  the  dextrose  according  t6 
the  Allihn  method  on  page  407. 

The  weight  of  dextrose  multiplied  by  0.9  gives  the  weight  of 
starch.  Multiply  this  weight  by  5,  divide  by  the  weight  of  paper 
taken  and  multiply  by  100  to  obtain  the  percentage  of  starch  in 
the  paper.  At  least  two  50  cc.  portions  of  the  neutral  dextrose 
solution  should  be  thus  analyzed  and  the  average  result  taken. 

NOTES. — (1)  The  saliva  is  obtained  by  chewing  paraffin  wax  and  collect- 
ing the  saliva  in  a  beaker.  Then  add  one-half  to  two-thirds  its  volume  of 
distilled  water  and  filter.  The  saliva  should  be  tested  with  starch  to  be  sure 
that  it  is  active. 

(2)  No  method  is  known  which  will  accurately  ascertain  the  amount  of 
starch  in  papers.     The  above  method,  however,  is  probably  the  most  nearly 
accurate,  as  cellulose  is  not  appreciably  affected  by  saliva. 

(3)  This  method  depends  upon  the  fact  that  the  diastase  in  saliva  will 
hydrolyze  starch  but  will  not  hydrolyze  the  cellulose  of  paper.     It  some- 
times happens,  however,  that  saliva  is  not  active  towards  starch  and  it  should, 
therefore,  always  be  tested  by  running  a  "blank"  on  a  little  starch  and  noting 
by  means  of  the  iodine  test  whether  the  starch  is  completely  hydrolyzed. 

Detection  of  Faulty  Sizing.* — Draw  a  strip  of  the  paper  over 
the  surface  of  an  iron  tannate  ink  and  allow  it  to  drain  and  dry 
naturally.  Examine  the  inked  surface  under  the  microscope. 
A  well-sized  paper  will  show  no  indication  of  the  fiber  having 
absorbed  ink,  and  the  entire  surface  will  be  uniformly  and  lightly 
colored,  as  indicated  in  Fig.  21.  In  more  poorly  si&ed  paper 
blotches  of  fibers  absorb  the  ink,  as  shown  in  Fig.  22  and  Fig.  23. 
Fig.  236  shows  water-leaf  filter  paper,  indicating  by  the  darker 
colors  that  the  fibers  have  absorbed  the  ink. 

NOTES. — (1)  All  the  papers  shown  in  these  plates  (except  Fig.  23&)  are, 
according  to  the  ordinary  methods  of  testing,  well-sized  and  practically 
identical. 

(2)  A  paper  well-sized  tlyoughout  should  also  show  a  uniform  coloring 
when  the  surface  has  been  rubbed  with  an  ink  eraser,  the  loose  particles 
brushed  off  and  the  paper  treated  with  ink  as  above. 

*  United  States  Dept.  of  Agriculture,  Bureau  of  Chem.  Cir.  No.  107. 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS       359 


FIG.  21.— Appearance  of  Well-sized  Paper  after  Test  with  Iron  Tannate  Ink. 


360 


TECHNICAL  METHODS  OF  ANALYSIS  . 


FIG.  22. — Appearance  of  Poorly-sized  Papers  in  Which  Blotches  of  Fibers 

Absorb  the  Ink. 


WOOD,  PAPER  AND  PAPER-MAKING  MATERIALS      361 


FIG.  23a. — Appearance  of  Paper  with  Inferior  Sizing. 


FIG.  236.— Water-leaf  Filter  Taper,  Showing  Ink  Absorbed. 


362  TECHNICAL  METHODS  OF  ANALYSIS 


TARNISHING  TEST  FOR  PAPER 

General. — A  paper  which  is  to  be  used  for  wrapping  silver- 
ware should  be  essentially  free  from  active  sulfur  compounds. 
The  method  of  testing  so-called  "  anti-tarnish"  paper  consists,  in 
general,  of  comparing  the  sample  to  be  tested  with  special  papers 
impregnated  with  0.001%  and  0.0001%  Na2S  solutions,  the  sulfide 
test  in  each  case  being  made  under  prescribed  conditions  by  a 
hydrogen  evolution  method  and  lead  acetate  paper. 

Preparation  of  Special  Impregnated  Papers. — Make  the 
special  papers  from  10  cm.  best  white  filter  paper,  each  of  which 
weighs  approximately  0.6  gram.  Prepare  the  following  solutions: 

(a)  Dissolve  3  grams  of  fresh  sodium  sulfide  crystals  in  100 
cc.   of  distilled  water.     (3  grams  of  Na2S-9H2O  are  equivalent 
to  1  gram  of  Na2S.) 

(b)  Dilute  1  cc.  of  solution  (a)  to  1  liter  to  make  a  0.001% 
solution. 

(c)  Dilute  10  cc.  of  solution  (b)  to  100  cc.  to  make  a  0.0001% 
solution. 

Saturate  the  filter  paper  in  solutions  (b)  and  (c)  and  dry  in  air. 
Considerable  quantities  of  these  papers  may  be  made  at  one  time 
and  stored  in  separate,  tightly  stoppered  bottles  labeled: 

"  0.001%  Na2S  Paper  for  Tarnishing  Test." 

"  0.0001%  Na2S  Paper  for  Tarnishing  Test." 
The  papers  may  also  be  torn  into  four  equal  segments,  each  seg- 
ment (0.15  gram)  being  sufficient  for  one  test. 

Materials  Required. — (1)  Four  500  cc.  flat  bottom  flasks, 
approximately  7  inches  high ;  (2)  Granulated  zinc  (arsenic  free) ; 
(3)  15%  HC1  solution;  (4)  Lead  acetate  test  paper,  moistened; 
(5)  Absorbent  cotton. 

Method. — Into  each  flask  put  2  grams  of  granulated  zinc  and 
0.15  gram  of  paper  torn  into  small  pieces.  The  4  flasks  are  for 
the  following  papers:  (1)  Sample;  (2)  Pure  filter  paper  (for  a 
"blank");  (3)  0.001%  Na2S  paper;  and  (4)  0.0001%  Na2S 
paper. 

Add  to  each  flask  25  cc.  of  15%  HC1  (free  from  As).  Into 
the  neck  of  the  flask  insert  a  loose  plug  of  cotton  to  a 
depth  of  about  1.5  inches.  Above  the  cotton  place  a  piece  of 
moistened  lead  acetate  test  paper  about  1  inch  square,  and  cover 


WOOD,   PAPER  AND   PAPER-MAKING  MATERIALS        363 

this  loosely  with  a  final  plug  of  cotton.  Set  the  4  flasks  in  a  pan 
or  tub  containing  water  at  room  temperature  to  a  depth  of  0.25- 
0.50  inch,  in  order  to  prevent  any  considerable  rise  of  temperature 
of  the  contents  of  the  flask.  The  liberated  hydrogen  will  carry 
any  H^S  evolved  up  to  the  lead  acetate  paper,  which  will  darken. 
Examine  the  4  lead  acetate  papers  at  the  end  of  thirty,  sixty  and 
ninety  minutes  and  record  their  comparative  appearances. 

Interpretation  of  Results. — It  has  been  found  that  the  0.001% 
Na2$  paper  causes  some  tarnishing  when  held  in  contact  with  a 
polished  10-cent  piece  for  five  weeks.  Commercial  papers  known 
to  have  caused  tarnishing  of  polished  metal  goods  have  been  found 
to  be  more  reactive  under  this  test  than  the  0.001%  Na2S  paper. 
Therefore,  a  paper  to  be  acceptable  should  show  up  as  well  as 
the  0.0001%  Na2$  paper  (which  should  show  slight  discolora- 
tion in  about  sixty  minutes).  A  paper  between  0.0001%  and 
0.001%  Na2$  papers  is  dangerous;  while  those  that  are  inferior 
to  0.001%  Na2$  paper  should  be  unquestionably  rejected. 

In  reporting,  a  paper  superior  to  0.0001%  Na2S  paper  should 
be  classed  as  "safe";  those  between  0.0001%  and  0.001% 
as  "questionable";  and  those  inferior  to  0.001% 


COTTON  CELLULOSE  (COTTON  LINTERS)  FOR  NITRATION 

General.— U.  S.  Navy  Specification  65C5,  July  10,  1913, 
requires  that  cotton  for  nitrating  for  smokeless  powder  shall  con- 
tain not  over  7%  of  water,  not  over  0.4%  of  ether  extract,  not  over 
0.8%  of  ash  and  only  traces  of  lime  salts;  and  that  it  shall  be  free 
from  hypochlorites,  dirt  and  foreign  matter.  This  is  essentially 
the  same  as  the  Joint  Powder  specifications  which  require  the  use 
of  a  bleached  cellulose  containing  not  more  than  0.4%  of  extractive 
matter,  not  more  than  0.8%  of  ash,  and  state  that  it  should  not 
contain  more  than  "  traces  "  of  lime,  chlorides  and  sulfates. 

For  some  commercial  grades  of  nitrocellulose  unbleached 
cotton  is  used,  but  the  methods  of  analysis  are  the  same  as  for 
bleached  cotton. 

The  routine  analysis  of  cotton  includes  the  determination  of 
moisture,  ether  extract,  ash,  solubility  in  95%  H2SO4  and  solu- 
bility in  10%  KOH  solution.  The  furfural  value  is  also  fre- 


364  TECHNICAL  METHODS  OF  ANALYSIS 

quently  determined,  and  on  crude  fiber  the  amount  of  "  dust  " 
is  determined  by  a  sieving  test.  It  is  also  sometimes  desirable 
to  determine  the  copper  number. 

Sampling. — In  sampling  fiber  in  bales,  take  a  section  extending 
from  one  side  to  approximately  the  center  from  each  bale  sampled, 
and  take  samples  from  not  less  than  one-tenth  of  the  bales  in  the 
lot.  In  sampling  crude  fiber,  make  special  note  of,  and  take  sam- 
ples from,  any  bales  showing  large  proportions  of  moldy  fiber  or 
of  very  oily  fiber,  as  indicated  by  a  strong  yellow  color. 

Blend  the  samples  for  moisture  quickly  and  thoroughly  by 
hand  and  place  a  sample  of  about  20  grams  in  a  previously  weighed 
glass  or  tin  vessel  with  a  tightly  fitting  cover.  Open  up  the 
remainder  of  the  sample  by  hand,  or  in  a  mill  or  picker  if  available, 
and  after  being  thoroughly  blended,  reduce  to  proper  size  by  quar- 
tering, and  dry  at  105°  C. 

Make  all  determinations,  except  moisture  and  dust,  on  the 
dry  sample. 

Moisture. — Take  about  20  grams  of  the  sample  prepared  for 
moisture  determination  and  weigh  under  conditions  to  avoid 
changes  in  moisture  content.  Dry  at  105°  C.  for  three  hours,  or 
if  the  moisture  is  high,  as  may  happen  with  samples  taken  from 
bales  that  have  been  exposed  to  rain,  until  constant  weight  is 
reached.  Calculate  the  loss  in  weight  to  per  cent  of  the  sample  as 
received. 

NOTE. — Instead  of  determining  the  moisture  on  a  large  scale  and  using 
portions  of  this  dried  material  for  subsequent  tests,  it  is  permissible  to  run  the 
tests  on  the  sample  as  received  and  calculate  results  to  the  dry  basis;  pro- 
vided, however,  that  the  moisture  is  not  excessive  (5-10%)  and  that  the 
sample  is  kept  where  it  does  not  lose  or  gain  moisture. 

Ash. — Place  at  least  5  grams  of  dry  material,  prepared  as 
above  in  a  platinum  or  fused  silica  dish  of  80-100  cc.  capacity  and 
ignite  in  a  muffle  or  over  a  burner  to  complete  incineration  at  a 
low  red  heat,  taking  care  to  avoid  loss  of  ash  by  air  currents  during 
handling.  Finally  cool  the  dish  and  contents  in  a  desiccator  and 
weigh.  Calculate  the  result  to  per  cent  of  the  dry  weight  of  the 
cotton. 

NOTE. — The  Powder  Specifications  call  for  the  digestion  of  a  1.5  gram 
sample  with  a  little  pure  HNO3  and  incineration  at  a  red  heat.  The  use  of 
the  smaller  sample  of  cotton  and  a  higher  temperature  of  incineration,  how- 
ever, is  likely  to  give  lower  results. 


WOOD,   PAPER  AND  PAPER-MAKING  MATERIALS      365 

Ether  Extract. — Extract  thoroughly  about  5  grams  of  the  dry 
material  with  pure  ethyl  ether  in  a  suitable  extraction  apparatus 
(preferably  Knorr's;  see  Eimer  &  Amend  Catalog,  No.  3185)  for 
about  eight  hours  or  until  further  extraction  removes  no  additional 
substances  soluble  in  ether.  Weigh  the  extractive  matter  after 
drying  at  100°  C.  to  constant  weight,  and  calculate  the  result 
(after  deducting  the  weight  of  any  residue  in  the  ether)  to  per  cent 
of  the  dry  weight  of  the  material.  Take  care  to  have  the  extractive 
matter  free  from  fine  particles  of  fiber  which  may  be  carried 
through  mechanically.  After  extraction  with  ether,  the  sample 
may  be  dried  and  used  for  the  determination  of  non-cellulose,  as 
below. 

Non-Cellulose.— Tho  H2S04  used  must  be  within  0.5%  of 
95%  strength.  Make  the  determination  by  treating  5  grams  of 
the  dry  sample  at  about  20°  C.  with  50  cc.  of  the  acid  at  the  same 
temperature.  In  the  case  of  crude  fibers,  it  is  important  to  remove 
the  oils  by  extraction  with  ether  before  making  this  determination. 
Stir  the  fiber  vigorously  in  the  acid  for  five  minutes,  then  slowly 
pour  into  1  liter  of  cold  distilled  water.  Heat  the  aqueous  solution 
on  a  hot  plate  for  at  least  four  hours,  with  frequent  stirring.  It  is 
important  to  keep  the  temperature  at  99-100°  C.  and  to  main- 
tain the  level  of  the  liquid  constant.  Then  filter  out  the  insoluble 
matter  on  a  Gooch  crucible  with  a  carefully  prepared  asbestos  mat. 
Thoroughly  wash  the  contents  of  the  Gooch  crucible  with  boiling 
distilled  water  to  remove  the  last  traces  of  H2SC>4  and  then  dry 
for  three  hours  at  102-105°  C.  Cool  and  weigh  the  non-cellulose 
and  calculate  the  result  to  per  cent  on  the  dry  weight  taken.  It  is 
important  to  have  the  fiber  well  opened  up  and  free  from  lumps, 
as,  if  lumps  are  present,  a  higher  result  may  be  expected. 

Approximate  Cellulose. — Calculate  the  "  approximate  cel- 
lulose "  in  the  fiber  by  adding  together  the  percentages  of  ash, 
ether  extract,  and  non-cellulose  and  subtracting  from  100%. 

Solubility  in  Caustic. — Cellulose  is  insoluble  in  alkalies,  so 
that  in  a  crude  fiber  the  solubility  in  KOH  or  NaOH  is  a  measure 
of  the  non-cellulose  present.  In  a  purified  fiber  it  is  a  measure  of 
the  severity  of  bleaching,  and  indicates  the  amount  of  hydrocel- 
lulose  and  oxycellulose  present. 

Prepare  a  solution  of  pure  KOH  within  0.1%  of  10%  concen- 
tration by  dissolving  the  proper  weight  of  the  purest  obtainable 


366  TECHNICAL  METHODS  OF  ANALYSIS 

KOH  in  distilled  water.*  Carefully  check  the  strength  of  the 
solution  by  titration  with  standard  acid  and  phenolphthalein. 
It  must  be  carefully  protected  from  CO2,  as  carbonates  do  not  act. 

Dry  approximately  2  grams  of  the  sample  in  a  wide-mouth 
weighing  bottle  to  constant  weight  at  102-105°  C.,  transfer  the 
contents  of  the  bottle  to  a  250  cc.  Pyrex  glass  or  porcelain  beaker, 
add  100  cc.  of  the  solution,  cover  with  a  watch  glass  and  heat  at 
100°  C.  for  three  hours.  Heating  on  a  steam  bath  is  not  satis- 
factory for  this  purpose,  as  it  does  not  give  a  sufficiently  high 
temperature.  Care  must  be  taken  to  avoid  concentration  of  the 
solution  or  undue  oxidation  of  the  fiber  due  to  exposure  of  the 
alkali-soaked  fiber  to  the  air.  It  is  important  that  the  tempera- 
ture be  kept  within  99-101°  C.,  since  variations  in  temperature 
affect  the  result  materially. 

After  the  heating  is  completed,  pour  the  contents  of  the  beaker 
into  a  2-liter  beaker  containing  1  liter  of  distilled  water  and 
wash  any  residue  in  the  small  beaker  into  the  larger.  Then 
neutralize  the  alkali  with  a  decided  excess  of  acetic  acid,  the 
excess  of  acid  being  necessary  in  order  to  break  up  the  combina- 
tion of  alkali  and  cellulose.  Filter  the  undissolved  cotton  into  a 
weighed  Gooch  crucible  having  an  asbestos  mat  and  thoroughly 
wash  successively  with  hot  water,  alcohol  and  ether.  Then  dry 
rapidly  to  constant  weight  at  102-105°  C.  Calculate  the  loss  of 
weight  to  per  cent  of  the  dry  material. 

NOTE. — In  making  this  determination  on  crude  fiber,  the  amount  soluble 
in  hot  water  alone  is  deducted  from  the  total  and  expressed  separately,  and  a 
further  correction  must  be  made  for  the  per  cent  of  oils  extracted  by  ether  and 
the  per  cent  of  ash  which  goes  into  solution  in  the  acetic  acid,  though  these 
corrections  are  not  necessary  on  bleached  fibers.  In  order  to  determine 
the  amount  of  ash  which  goes  into  solution,  an  ash  determination  must  be 
made  on  the  fiber  after  treatment. 

Furfural  Value  (Pentosans). — Preparation  of  Reagents. — Test 
the  purity  of  the  phloroglucinol  by  dissolving  a  small  quantity 
in  a  few  drops  of  acetic  anhydride,  then  heat  almost  to  boiling  and 
add  a  few  drops  of  cone.  H2SO4.  A  violet  color  indicates  the  pres- 
ence of  diresorcin.  If  the  phloroglucinol  gives  more  than  a  faint 
coloration  it  should  be  purified  by  the  following  method  : 

*  A  solution  of  pure  NaOH  within  0.1%  of  7.14%  may  be  used  instead 
of  a  10%  KOH  solution. 


WOOD,  PAPER  AND  PAPER-MAKING  MATERIALS       367 

Heat  in  a  beaker  about  300  cc.  of  12%  HC1  (1  :  2)  and  11 
grams  of  the  commercial  phloroglucinol.  Add  the  latter  in  small 
quantities  at  a  time,  stirring  constantly  until  it  has  almost  entirely 
dissolved  (some  impurities  may  resist  solution).  Pour  into  a 
sufficient  quantity  of  the  same  HC1  (cold)  to  make  the  volume 
1500  cc.  Let  stand  at  least  overnight,  better  several  days,  to 
allow  the  diresorcin  to  crystallize  out,  and  filter  immediately 
before  using.  The  solution  may  turn  yellow,  but  this  does  not 
interfere  with  its  usefulness.  In  using,  add  the  volume  containing 
the  required  amount  to  the  distillate. 

Determination. — Place  a  weighed  quantity  of  the  material, 
chosen  so  that  the  weight  of  furfural  phloroglucid  obtained  shall 
not  exceed  0.300  gram,  in  a  flask  together  with  100  cc.  of  12%  HC1 
and  several  pieces  of  recently  heated  pumice  stone.  Place  the 
flask  on  a  wire  gauze,  connect  with  a  condenser,  heat  rather  gently 
at  first,  and  so  regulate  as  to  distill  over  30  cc.  in  about  ten  min- 
utes, the  distillate  passing  through  a  small  filter' paper.  Replace 
the  30  cc.  driven  over  by  a  like  quantity  of  the  dil.  HC1,  added  by 
means  of  a  separatory  funnel  in  such  a  manner  as  to  wash  down  the 
particles  adhering  to  the  sides  of  the  flask,  and  continue  the  process 
until  the  distillate  amounts  to  360  cc.  To  the  total  distillate  grad- 
ually add  a  quantity  of  phloroglucinol  (purified  if  necessary)  dis- 
solved in  12%  HC1  and  thoroughly  stir  the  resulting  mixture. 
The  amount  of  phloroglucinol  used  should  be  about  double  that 
of  the  furfural  expected. 

.  The  solution  first  turns  yellow,  then  green,  and  very  soon  an 
amorphous  greenish  precipitate  appears,  which  grows  rapidly 
darker,  till  it  finally  becomes  almost  black.  Make'  the  solution 
up  to  400  cc.  with  12%  HC1  and  let  stand  overnight. 

Filter  the  amorphous  black  precipitate  through  an  asbestos 
felt  in  a  Gooch  crucible  which  has  been  previously  dried  and 
weighed  in  a  weighing  bottle.  Wash  carefully  with  150  cc.  of 
water  in  such  a  way  that  the  water  is  not  entirely  removed  from 
the  crucible  until  the  very  last,  then  dry  for  four  hours  at  the 
temperature  of  boiling  water,  cool  and  weigh  in  the  weighing  bottle, 
the  increase  in  weight  being  reckoned  as  furfural  phloroglucid, 
Calculate  to  furfural,  using  the  following  formulae  given  by  Krober: 

(a)  For  weight  of  phloroglucid,  w,  less  than  0.030  gram: 
Furfural  =  (w+0.0052)  X0.5170. 


368  TECHNICAL  METHODS  OF  ANALYSIS 

(6)  For  weight  of  phloroglucid,  w,  more  than  0.300  gram: 
Furfural  =  (w+0.0052)  X0.5180. 

(c)  For  weight  of  phloroglucid,  w,  between  0.030-0.300  gram: 
Furfural  =  (w+0.0052)  X0.5185. 

Copper  Value. — Cut  3  grams  of  the  sample  into  small  pieces 
and  mix  with  150  cc.  of  boiling  water.  Heat  to  boiling  50  cc.  of 
Fehling's  copper  solution  and  50  cc.  of  Fehling's  alkaline  tartrate 
solution  *  and  add  to  the  sample.  Then  boil  the  whole  with  con- 
tinuous stirring  for  fifteen  minutes,  filter  and  wash  with  hot  water. 
Warm  the  residue  with  dil.  HNOs,  to  dissolve  out  the  absorbed  Cu, 
and  filter.  Determine  the  Cu  electrolytically  on  a  rotating 
cathode.  Calculate  the  "  copper  value  "  or  "  copper  number," 
which  is  the  weight  in  grams  of  metallic  Cu  thus  obtained  per  100 
grams  of  dry  material. 

NOTES. — (1)  When  this  determination  is  used  as  a  basis  of  acceptance 
or  rejection,  6  samples  shall  be  selected  from  various  parts  of  the  bale.  The 
copper  value  of  each  of  these  samples  shall  be  determined  as  above  and  the 
highest  copper  value  of  each  of  the  6  shall  be  considered  the  copper  value  of 
the  lot. 

(2)  Most  specifications  require  that  the  copper  value  shall  not  exceed  2. 

(3)  The  copper  value  is  a  measure  of  the  oxy-cellulose  and  indicates  whether 
the  material  has  been  over-bleached.     Mitchell  and  Prideaux:  "Fibers  in  the 
Textile  Industry,"  page  93,  give  representative  copper  numbers  as  follows: 

Surgical  Cotton  Wool 1.6 

Parchment  Paper 4.2 

Bleached  Sulfite  Pulp 3.9 

Overbleached  Sulfite  Pulp . 193 

REFERENCES. — Part  of  the  above  method  was  originally  furnished  us  by 
W.  F.  Allen  of  the  Meridian  Cellulose  Co.,  and  is  the  method  used  by  E.  I. 
Du  Pont  de  Nemours  &  Company.  The  procedure  for  Furfural  Value  is 
the  tentative  method  of  the  Assoc.  of  Official  Agricultural  Chemists  pub- 
lished in  its  Journal,  Methods  of  Analysis  (1916),  page  110. 

WOOD  DISTILLATE  PRODUCTS 

General. — The  chief  hard  woods  used  in  this  country  for  dis- 
tillation are  beech,  birch  and  maple.     The  products  of  distilla- 
tion are  gas,  crude  pyroligneous  liquor  and  charcoal.     This  method 
is  concerned  only  with  the  analysis  of  the  crude  liquor,  which 
*  Use  the  Soxhlet  modifications  (see  page  3) . 


WOOD,  PAPER  AND  PAPER-MAKING  MATERIALS       369 

consists  essentially  of  acetic  acid,  crude  wood  alcohol,  tar,  and 
water. 

ANALYSIS  OF  CRUDE  LIQUOR 

Tar. — In  commercial  practice  the  bulk  of  the  tar  is  mechan- 
ically separated,  but  the  liquor  always  contains  more  or  less  dis- 
solved or  suspended  tar. 

Weigh  the  whole  sample  and  determine  its  volume.  Separate 
mechanically  as  much  of  the  tar  as  possible,  weighing  the  amount 
thus  separated.  If  desired,  its  sp.  gr.  may  be  determined  by  the 
Westphal  balance  or  a  pycnometer. 

Determine  the  dissolved  tar  as  later  described  and  add  the 
amount  to  the  amount  obtained  by  mechanical  separation. 

Acetic  Acid. — Place  100  cc.  of  the  liquor  in  a  weighed  retort 
or  distilling  flask,  set  up  in  an  oil  bath  and  connect  with  a  Liebig 
condenser.  Place  a  thermometer  in  the  oil  and  gradually  heat 
the  oil  bath  to  140°  C.,  collecting  the  distillate  in  a  250  cc. 
graduated  flask.  Keep  the  temperature  of  the  bath  at  140°  C. 
until  nothing  more  comes  over.  In  the  flask  there  will  remain 
about  10  cc.  of  tar  which  still  contains  some  acetic  acid.  The 
last  traces  of  acid  must  be  blown  over  by  a  current  of  steam,  keep- 
ing the  oil  bath  at  150°  C.  and  collecting  the  distillate  in  the  flask 
with  the  main  distillate.  Make  up  the  distillate  to  the  mark  at 
15.5°  C.  Pipette  out  50  cc.  at  the  same  temperature  and  titrate 
with  N  NaOH  and  phenolphthalein.  Calculate  to  acetic  acid 
and  to  calcium  acetate. 

CALCULATIONS.— 1  cc.  N  NaOH  =  0.06004  gram  HC2H302. 

=  0.07907  gram  Ca(C2H302)2. 

NOTE. — For  ordinary  purposes,  instead  of  blowing  over  the  last  traces  of 
acid  with  steam,  satisfactory  results  can  be  obtained  by  cooling  down  the 
flask,  adding  50  cc.  of  water  and  again  distilling  until  nothing  more  comes  over 
at  140°  C.  (See  U.  S.  Dept.  of  Agriculture,  Forest  Service,  Bulletin  129, 
page  6.) 

Dissolved  Tar. — The  residue  in  the  flask  from  the  distillation 
of  the  acetic  acid  represents  the  dissolved  tar.  Cool  and  weigh, 
and  add  the  amount  to  the  tar  mechanically  separated  above. 

Crude  Wood  Alcohol. — Place  1  liter  of  the  crude  liquor  in  a 
round  bottom  1500  cc.  flask.  Set  the  flask  in  an  oil  bath  and 


370  TECHNICAL  METHODS  OF  ANALYSIS 

connect  to  a  vertical  condenser.  Distill  until  500  cc.  of  distillate 
have  been  collected.  Neutralize  the  distillate  with  NaOH  and 
distill  again  from  a  smaller  flask  until  50%  has  distilled  off  (250  cc.). 
This  distillate  is  still  too  dilute  to  estimate  the  alcohol  accurately, 
especially  as  it  still  contains  methyl  acetate  which,  owing  to  its 
high  gravity,  would  make  the  results  come  low.  Hence,  the  dis- 
tillate should  again  be  neutralized  with  NaOH  and  redistilled, 
collecting  in  a  graduated  100  cc.  flask.  Stop  the  distillation  just 
before  100  cc.  have  come  over,  cool  to  15.5°  C.  and  make  up  to 
volume  accurately  with  distilled  water.  Determine  the  sp.  gr. 
of  the  distillate  at  15.5°  C.  with  a  Westphal  balance,  or  preferably 
with  a  pycnometer.  From  the  sp.  gr.  calculate  the  percentage  of 
methyl  alcohol  in  this  distillate,  both  by  weight  and  by  volume, 
and  figure  back  to  the  original  sample.  (See  page  458.) 

NOTES. — (1)  Great  care  must  be  exercised  in  making  the  distillation  not 
to  lose  alcohol.  A  vertical  condenser  is  preferable  to  a  horizontal  one  and  the 
end  of  the  condenser  should  run  well  down  into  the  neck  of  the  flask. 

(2)  By  this  method  all  the  substances  which  accompany  methyl  alcohol, 
such  as  acetone,  acetaldehyde,  allylalcohol,  etc.,  are  calculated  as  methyl 
alcohol.  The  results,  therefore,  should  be  reported  as  Crude  Wood  Alcohol 
and  if  the  determination  of  the  true  methyl  alcohol  content  is  desired,  use  the 
method  of  Zeisal  and  Stritar.  (Zeit.  fur  Anal.  Chem.  29,  359;  42,  579;  43, 
387.) 

ANALYSIS  OF  PRODUCTS  OF  CRUDE  LIQUOR 

Acetic  Acid. — Two  kinds  of  acetic  acid  from  wood  are  recog- 
nized : 

(1)  Crude  wood  acid,  containing  about  6%  of  acetic  acid. 

(2)  Rectified  wood  acid,  so-called  "  light  vinegar/'  which  has 
a  similar  strength. 

The  first  product  is  obtained  from  the  crude  wood  liquor  by 
distilling  off  the  alcohol  and  diluting  the  residue  in  the  still  with 
water  until  it  has  an  acid  content  of  6%.  The  second  product 
is  made  from  a  single  distillation  of  the  crude  wood  acid,  which 
yields  a  pale  yellow  liquid  still  containing  about  6%  acid. 

The  determination  of  the  strength  of  the  acetic  acid  can 
be  made  in  the  case  of  tar-free  wood  acid  (product  2)  by  titrating 
with  N  NaOH  and  phenolphthalein.  In  the  case  of  the  raw  acid, 
however,  the  end  point  is  often  difficult  to  obtain  with  certainty 
and  it  is  best  to  dilute  it  1  :  10  before  attempting  titration. 


WOOD,  PAPER  AND  PAPER-MAKING  MATERIALS       371 

The  tar  contained  in  crude  liquor  gives  a  strong  coloration 
with  NaOH  and  it  is  often  impossible  to  get  an  accurate  titration. 
This  may  be  overcome  by  using  litmus  or  phenolphthalein  as  an 
outside  indicator  on  a  white  porcelain  tile.  For  accurate  results, 
however,  it  is  preferable  to  make  a  distillation  and  titrate  the  dis- 
tillate as  described  in  the  first  part  of  the  method. 

Acetone. — The  acetone  content  of  crude  wood  alcohol  is 
determined  by  the  well-known  Messinger  method,  which  is 
described  on  page  72. 

Total  Ketones. — For  general  purposes  a  determination  of  the 
acetone  content,  as  obtained  by  the  Messinger  method,  gives 
sufficient  information.  In  case  the  total  ketone  content  is  desired, 
the  method  of  Deniges  (Comp.  rend.  127,  963)  may  be  employed. 


CHAPTER   IX 
ANALYSIS   OF  TEXTILES  AND  TEXTILE  FIBERS 

STRUCTURAL  ANALYSIS  OF  TEXTILE  FABRICS 

General. — The  following  is  a  brief  outline  of  the  determina- 
tions usually  desired  in  making  structural  analyses  of  textile  fab- 
rics and  a  description  of  the  procedures  employed. 

Fiber  Composition. — See  page  377. 

Ash  (Mineral  Weighting). — Determine  the  ash  on  2-5  grams 
of  sample  in  a  porcelain  crucible  and  report  the  percentage  as 
mineral  weighting.  The  weighting  usually  consists  principally 
of  tin  salts,  Fe2O3,  Prussian  blue,  Si02  and  P2O5.  Tin  phosphate 
is  not  uncommon.  The  estimation  of  the  mineral  matter  is  of 
special  importance  in  the  examination  of  such  fabrics  as  water- 
proof rain-coats,  window  shades,  bookbinders'  cloth,  fireproof 
cloth,  heavily  weighted  silks,  etc.  Black  silks  sometimes  contain 
250%  of  weighting,  based  on  the  weight  of  the  silk. 

NOTE. — In  waterproof  goods  ammonium  salts  often  occur  and  these,  of 
course,  would  be  volatilized  in  ashing  and  must  be  tested  for  on  a  separate 
portion. 

Sizing  Materials. — The  sizing  usually  consists  of  starch,  gums, 
glue,  oil,  fat  or  wax.  Nearly  all  textiles  will  show  the  presence  of 
small  amounts  of  various  sizing  materials  which  it  is  necessary 
to  use  in  dyeing  and  finishing  in  order  to  produce  the  desired  feel 
and  finish.  It  is  seldom  necessary  to  determine  this  quantitatively. 
Boiling  hot  water  or  a  solution  of  "  diastafor  "  will  remove  starch. 
Gums  are  also  as  a  general  rule  soluble  in  water  and  so  is  glue. 
Oils  and  fats  can  be  removed  by  ether  extraction  and  waxes  by 
alcohol  extraction. 

When  the  sizing  consists  of  starch  and  British  gum  (dextrin), 
the  amount  may  be  determined  as  follows:  Dry  approximately 
5  grams  to  constant  weight  at  100°  C.  Determine  the  loss. 

372 


ANALYSIS  OF  TEXTILES  AND  TEXTILE  FIBERS      373 

Boil  the  dried  sample  in  water  for  ten  minutes.  Rinse  well  and 
digest  two  hours  at  60°  C.  in  a  solution  of  15  cc.  of  commercial 
"  diastafor  "  in  500  cc.  of  water.  Wash  well  in  hot  EkO,  boil 
one  hour  in  500  cc.  of  distilled  water,  wash  again,  dry  at  100°  C. 
and  weigh. 

total  loss— moisture  loss 

CALCULATION.— %  size  =-  .  .  -X100. 

wt.  original  sample 

Bursting  Strength. — Bursting  strength  is  determined  on  the 
Perkins  Mullen  tester  (Fig.  18,  page  349)  and  reported  in  pounds 
per  square  inch.  The  average  of  at  least  5  tests,  and  preferably 
10,  should  be  taken. 

Tensile  Strength  and  Stretch. — There  are  two  methods  of 
determining  tensile  strength  as  follows  : 

(A)  STRIP  METHOD. — Cut  pieces  of  fabric,  both  in  the  warp 
and  in  the  filling  direction,  each  piece  8  inches  long  and  1.5  inches 
wide.     Ravel  down  to  the  desired  width,  or  the  specified  number  of 
threads  per  inch,  by  removing  approximately  an  equal  number  of 
threads  from  each  side.     Insert  these  strips  in  the  test  machine. 
(In  case  stretch  is  to  be  determined,  2  parallel  marks  should  be 
made  on  the  specimen  3  inches  apart,  and  the  lower  edge  of  the 
jaws  should  be  clamped  even  with  these  marks.)     After  clamp- 
ing the  jaws,  apply  power  to  the  machine  to  make  the  sepa- 
ration of  the  jaws  proceed  at  a  uniform  rate  of  20  inches  per 
minute. 

From  the  breaking  strength  of  the  strip  and  its  width  calculate 
the  tensile  strength  of  the  fabric  in  each  direction  in  pounds  per 
inch.  Also  measure  the  elongation  or  stretch  at  time  of  breaking 
between  the  lines  drawn  3  inches  apart.  Express  the  stretch 
results  in  percentage  on  3  inches. 

(B)  GRAB  METHOD. — It  is  necessary  to  use  this  method  in  case 
of  hosiery  and  knitted   goods  which  cannot  be  raveled  down. 
Tests  should  be  made  on  the  Scott  tester.     Test  specimens  should 
be  5  inches  long  by  2  inches  wide  and  cut  in  each  direction.     On 
each  piece  as  it  lies  flat  without  tension  on  a  smooth  surface,  draw 
pencil  lines  along  the  thread  vertically  and  0.5  inch  from  each 
edge  so  that  1  inch  of  fabric  will  be  between  them.     Then  draw 
pencil  lines  along  the  thread  horizontally  and  1  inch  apart  in  the 
center  of  the  specimen.     The  clamps  of  the  machine  consist  of  2 


374  TECHNICAL  METHODS  OF  ANALYSIS 

jaws,  one  at  least  2  inches  wide  and  the  other  1  inch  wide.  Clamp 
the  specimen  in  the  2  jaws  of  the  machine  securely,  taking  care 
that  the  threads  being  tested  are  parallel  to  the  direction  of  pull, 
and  the  cross  threads  are  at  right  angles  to  it.  Have  the  length 
of  the  test  specimen  between  jaws  exactly  1  inch.  Report  the 
tensile  strength  in  pounds  per  inch  and  the  increase  in  length  of 
the  1  inch  portion  as  the  'elongation,  either  in  units  of  length  or  as 
percentage  of  1  inch. 

NOTE. — On  tensile  and  elongation  tests  the  average  of  at  least  5  and  prefer- 
ably 10  tests  in  each  direction  should  be  made. 

Folding  Endurance. — Materials  such  as  silk,  book-cloth,  win- 
dow shades,  etc.,  are  subject  to  folding  to  a  considerable  extent  in 
actual  use.  In  such  cases  a  folding  endurance  test  will  show  to 
what  extent  they  may  be  expected  to  resist  deterioration  from  this 
cause.  Make  the  test  on  the  Schopper  folding  machine  (Fig.  17, 
page  348).  Cut  strips  from  each  direction  about  30  mm.  wide  and 
ravel  down  until  they  are  exactly  15  mm.  wide.  Insert  in  the 
stand,  under  a  machine  and  determine  the  number  of  double 
folds  they  will  tension  of  1  kilo,  before  breaking.  At  least  5 
tests,  and  preferably  10,  should  be  made  in  each  direction  and  the 
average  figures  reported. 

Thread  Count. — This  term  is  used  in  reporting  the  number  of 
threads  per  inch  in  the  fabric  in  each  direction.  The  greater 
the  number  of  threads  per  inch,  the  finer  or  closer  is  the  texture 
of  the  fabric.  Count  the  threads  in  each  direction  with  a  special 
counting  glass  and  report  the  number  of  threads  in  the  filling  as 
"  picks  per  inch  "  and  in  the  warp  as  "  threads  per  inch." 

Twist. — This  term  is  used  in  determining  the  number  of  twists 
per  inch  in  a  thread.  It  is  also  customary  to  designate  them  as 
right  or  left  twists. 

Size  of  Yarn. — The  terms  "  yarn  number  "  and  "  size  "  are 
commonly  used  to  indicate  the  length  of  yarn  per  unit  of  weight. 
There  are  many  systems  of  numbering  in  use  which  are  for  the 
most  part  based  on  arbitrary  quantities,  differing  according  to 
the  kind  of  material  or  the  locality,  or  even  the  preference  of  the 
individual.  For  use  in  this  laboratory,  we  have  adopted  the 
"  Fixed  Weight  System  "  in  which  the  count  represents  the  length 
(hanks  or  yards)  of  a  fixed  weight.  In  this  system  the  count 
number  is  inversely  proportional  to  the  size  of  the  yarn.  The 


ANALYSIS  OF   TEXTILES  AND   TEXTILE  FIBERS       375 

basis  of  a  No.  1  yarn  on  the  "  Fixed  Weight  System  "  is  shown  in 
the  following  table : 

FIXED  WEIGHT  SYSTEM 


Material 

Unit 

Usage 

Woolen 

1,600-yd.  lengths  per  pound 

Anglo-American 

Cotton 

840-yd.  lengths  par  pound 

World 

Worsted 

560-yd.  lengths  pee  pound 

Anglo-American 

Linen 

300-yd.  lengths  per  pound 

World 

Raw  Silk 

1-yd.  lengths  per  ounce 

England 

A  No.  2  cotton  would  contain  2X840  yards  per  pound  and 
a  No.  3  cotton,  3X840. 

Ply  yarn  is  numbered  to  indicate  the  number  of  strands  and  the 
size  of  a  single  yarn,  thus:  2-40  means  that  2  strands  of  size  40 
are  placed  together  to  form  a  2-ply  yarn.  Spun  silk  is  an  excep- 
tion to  this  rule,  the  first  number  indicating  the  count  or  size  of 
the  ply  yarn  and  the  second  the  number  of  strands,  thus:  20-2 
spun  silk  indicates  that  2  strands  of  40  size  have  been  doubled  or 
twisted  making  a  2-ply  yarn  equal  to  a  single  20. 

Silk  is  usually  numbered  either  by  the  dram  or  the  denier 
system.  The  dram  system  represents  the  number  of  drams  per 
1000  yards;  the  denier  system  represents  the  number  of  grains 
per  638  yards. 

By  weighing  a  given  length  of  yarn  it  is  possible  to  calculate 
the  number  of  unit  lengths  per  unit  weight,  and  the  size  of  the 
yarn. 

Weight. — The  weight  of  fabrics  is  reported  as  ounces  per 
square  yard.  In  case  of  hosiery  it  is  reported  as  weight  per  dozen 
pairs  of  hose. 

Weigh  a  piece  of  definite  size  and  calculate  the  weight  per 
square  yard. 

CALCULATION. — Grams  per  sq.  in.X45.71  =  oz.  per  sq.  yard. 

Special  Tests. — (1)  FASTNESS  TO  LIGHT. — The  rational  test 
for  determining  fastness  to  light  of  dyed  goods  is  exposure  to 
bright  sunlight.  This  is  not  practical,  however,  as  it  requires  too 
much  time.  A  fairly  satisfactory  indication  of  the  relative  fast- 
ness to  light  can  be  obtained  by  exposing  a  small  piece  of  the  goods 


376  TECHNICAL  METHODS  OF  ANALYSIS 

for  seven  hours  to  ultra-violet  light  and  comparing  with  a  piece  of 
the  original  goods.  In  the  case  of  very  fast  colors  it  is  sometimes 
desirable  to  make  a  much  longer  exposure. 

(2)  FASTNESS  TO  WASHING. — (A)  Cotton. — Dissolve  2  grams  of 
Ivory  soap  in  1000  cc.  of  water  and  immerse  a  piece  of  the  sample 
in  a  portion  of  this  solution  for  one-half  hour  at"  60°  C.,  together 
with  a  piece  of  white  cotton  and  a  piece  of  white  woolen  goods. 
If  the  color  strips  off  the  sample  and  stains  the  white  material, 
it  is  not  fast  to  washing. 

(B)  Wool. — Dissolve  2  grams  of  Ivory  soap  and  0.5  gram  of 
Na2COa  in  1000  cc.  of  water  and  wash  as  in  the  case  of  cotton  for 
one  hour  at  50°  C. 

(3)  FASTNESS  TO  PERSPIRATION. — Dissolve  50  grams  of  50% 
acetic  acid  and  100  grams  of  NaCl  in  a  liter  of  water.     Immerse  a 
portion  of  the  sample  in  this  solution  for  fifteen  minutes,  let  dry 
and  repeat  the  operation  twice.     Compare  the  final  dry  piece  with 
the  original  and  note  any  change. 

(4)  FASTNESS  TO  MUD  SPOTS. — Splash  a  sample  of  material 
with  street  mud,  let  dry,  brush  off  the  mud  and  note  the  effect. 

(5)  HOT  IRONING  TEST. — Iron  with  a  hot  iron  and  note  if  heat 
changes  the  color.     This  shows  the  sensitiveness  of  colors  to  heat 
and  in  many  cases,  especially  with  light  shades,  colors  will  be  found 
to  change  to  a  considerable  extent.     Most  of  them  assume  their 
original  shade  on  cooling,  but  in  some  cases  the  change  is  perma- 
nent.    Tlie  test  is  also  of  value  on  certain  classes  of  fabrics,  such 
for  instance  as  Bolivia  cloths,  where  hot  ironing,  especially  in  the 
presence  of  moisture,  tends  to  destroy  the  surface  finish  of  the 
fabric. 

In  the  case  of  heavily  weighted  silks,  continued  hot  ironing 
will  have  a  tendency  not  only  to  change  the  shade  of  some  of  the 
colors,  but  to  cause  the  material  to  deteriorate  and,  in  some 
instances,  to  crack  badly. 

Hosiery. — In  hosiery  analysis  the  terms  "  wales "  and 
"  courses  "  are  used  and  correspond  to  warp  and  filling,  respect- 
ively, in  woven  fabrics.  The  term  "  reinforcing  thread,"  used 
in  toe  and  heel,  applies  to  an  extra  thread  twisted  in  to  reinforce 
and  give  additional  strength.  The  weight  is  reported  in  ounces 
per  dozen  pairs. 


ANALYSIS  OF  TEXTILES  AND  TEXTILE  FIBERS        377 


FIBERS  IN  CLOTH  AND  YARNS 

General. — The  following  method  gives  the  procedure  to  be 
used  in  analyzing  a  complex  mixture  of  textile  fibers.  It  is  seldom 
that  more  than  two  fibers  are  found  in  the  same  fabric,  and  where 
the  fibers  are  known,  as  for  instance  in  a  wool-cotton  mixture,  the 
procedure  can  be  very  much  shortened. 

Moisture. — Weigh  2-5  grams  of  sample  in  a  glass-stoppered 
weighing  bottle  and  dry  at  100-110°  C.  to  constant  weight. 
Report  the  loss  as  moisture. 

Sizing  Materials,  etc. — Use  the  dry  material  from  the  moisture 
determination  and  boil  thoroughly  in  very  dil.  HC1.  The  solu- 
tion should  not  be  over  1%  in  strength  and  care  must  be  taken  not 
to  disintegrate  the  fibers.  If  the  fibers  are  much  weakened  or 
disintegrated,  it  is  well  to  repeat,  using  weaker  acid.  Repeat 
the  boiling  until  no  residue  is  found  upon  evaporating  a  few  drops 
of  the  liquid  on  a  watch  glass.  This  removes  mineral  loading 
matter  soluble  in  HC1,  finishing  materials,  and  more  or  less  dye- 
stuff,  as  well  as  other  materials  soluble  in  water.  Next  extract 
with  alcohol,  and  finally  with  ether,  until  all  soluble  material  is 
removed.  Dry  and  weigh.  This  gives  the  weight  of  anhydrous 
fibers,  together  with  any  mineral  matter  not  soluble  in  HC1.  Divide 
immediately  into  2  parts,  weighing  each.  Ash  one  portion.  This 
will  give  the  natural  insoluble  ash  of  the  fibers  and  any  insoluble 
loading  materials,  such  as  certain  mordants  and  tin  salts.  Cal- 
culate the  weight  back  to  percentage  of  the  original  material. 

Silk. — Heat  to  boiling  about  60  cc.  of  basic  ZnCk  solution,* 
and  immerse  in  it  the  second  portion  of  the  above  extracted  sam- 
ple. Remove  the  flame,  stir  the  sample  thoroughly  for  about 
one  minute  and  again  bring  to  boiling.  Transfer  immediately  to  a 
previously  weighed  Gooch  crucible,  using  the  insoluble  fibers 
(cotton  and  wool)  for  the  mat  of  the  crucible.  Remove  the  insol- 
uble fibers  to  a  beaker  containing  cold,  dil.  HC1  (5%).  Thor- 
oughly wash  in  the  beaker  by  agitation  and  again  filter.  Repeat 
the  process  several  times  to  remove  all  ZnC^,  using  weaker  acid 
solution  at  each  subsequent  washing.  Finally  remove  to  the 

*  The  zinc  chloride  solution  is  made  as  follows :  Add  an  excess  of  Zn  metal 
to  cone.  HC1  and  let  stand  twenty-four  hours.  Filter  through  glass  wool 
and  slightly  acidify  with  HC1. 


378  TECHNICAL  METHODS  OF  ANALYSIS 

crucible  and  finish  the  washing  with  several  portions  of  hot  water 
until  free  from  Cl.  Dry  at  100-105°  C.,  and  weigh.  The 
loss  in  weight  represents  silk  (and  in  certain  cases  a  portion  of  the 
sizing  material).  If  the  material  is  pure  natural  silk,  no  residue 
is  left  at  this  point  of  the  analysis. 

NOTE. — This  treatment  also  removes  artificial  silk. 

Wool. — Treat  the  above  residue  with  a  solution  of  approxi- 
mately 5%  KOH  and  boil  gently  for  ten  to  fifteen  minutes.  Pour 
into  500  cc.  of  cold  water,  let  stand  until  the  fibers  have  settled, 
and  decant  carefully  the  supernatant  liquor,  taking  care  to  avoid 
loss  of  any  fibers.  Filter  through  a  weighed  Gooch  crucible  and 
wash  with  hot  water,  and  finally  with  about  10  cc.  of  alcohol. 
Dry  and  weigh.  The  loss  in  weight  by  the  KOH  treatment  repre- 
sents wool. 

Cotton,  etc. — The  residue  in  the  crucible  at  this  stage  is  cotton, 
or  vegetable  fibers  (wood  fiber,  jute,  linen  and  similar  material). 
Ignite  and  weigh.  The  loss  represents  the  various  fibers,  the 
nature  and  approximate  proportions  of  which  must  be  determined 
microscopically  on  another  portion.  The  residue  in  the  crucible 
may  consist  of  asbestos,  mineral  wool,  etc.,  and  should  be  exam- 
ined qualitatively  and  microscopically. 

Cotton- Wool  Mixtures. — In  the  case  of  fabrics  consisting  only 
of  cotton  and  wool,  determine  the  moisture  as  above  described 
and  remove  sizing  materials,  if  necessary,  by  boiling  with  1% 
HC1  solution.  Wash  out  the  acid  and  dry  at  105°  C.  to  get  the 
total  weight  of  fibers.  Boil  the  residue  for  fifteen  to  twenty 
minutes  with  5%  KOH  solution  and  proceed  as  directed  above 
under  Wool,  the  final  residue  being  cotton. 

Calculation  of  Results. — About  5%  of  cotton  is  soluble  in  KOH 
solution.  To  obtain  the  true  weight  of  bone-dry  cotton,  there- 
fore, divide  the  actual  weight  of  cotton  by  0.95  and  also  subtract 
this  increment  from  the  wool  as  figured  by  loss  to  KOH.  Cal- 
culate the  percentages  of  the  various  fibers  on  the  bone-dry  basis. 

As  the  natural  moisture  of  cotton  fiber  is  different  from  that  of 
wool,  where  the  fabric  has  a  cotton  thread  in  one  direction  and 
wool  in  the  other,  the  threads  should  be  separated  and  the  moisture 
determined  on  each.  In  cases  where  wool  and  cotton  are  twisted 
together,  however,  this  is  not  possible.  The  U.  S.  Government 


ANALYSIS  OF  TEXTILES  AND   TEXTILE  FIBERS        379 

allows  a  re-gain  of  11%  in  wool  for  army  blankets,  etc.  For  silk 
the  re-gain  allowed  should  also  be  11%,  and  for  cotton  and  vege- 
table fibers  7%.  Where  it  is  not  possible  to  determine  the  moisture 
of  the  different  fibers,  the  air-dry  percentage  should  be  figured  by 
dividing  the  percentages  of  wool,  cotton  (vegetable  fiber)  and 
silk  by  0.89,  0.93  and  0.89,  respectively.  If  the  sum  then  exceeds 
100%  (showing  that  the  fabric  was  below  normal  moisture), 
correct  these  figures  by  multiplying  each  percentage  thus  obtained 

100 
by  -T-,  where  A  is  the  sum  total. 

A. 

EXAMPLE  : 

Preliminary  analysis:  Per  Cent 

Moisture  (loss  at  100°  C.) 8 . 74 

Sizing,  etc.  (loss  to  HC1) 3.28 

Fibers  (by  difference) 87 . 98 

Analysis  of  bone-dry  fibers : 

Silk  (loss  to  basic  ZnCl2) 22. 10 

Wool  (loss  to  KOH) 30.64 

Cotton  (residue) 47 . 26 

Cotton  (corrected,  47.26n-0.95) 49.75 

Wool  (corrected,  30.64-2.49) 28. 15 

Air-dry  analysis : 

Silk  (22.10-^-0.89) 24.83 

Wool  (28.15^-0.89) 31.63 

Cotton  (49 .75-^-0.93) 53.49 

Sizing,  etc 3.28 


Total 113.23 

100 
Final  corrected  analysis  (air-dry  analysis  figures  X  ) 

11  o.Jo 

Silk 21.93 

Wool 27.93 

Cotton 47.24 

Sizing,  etc 2 . 90 

100.00 

Distinction  between  Natural  and  Artificial  Silks.— The  princi- 
pal varieties  of  artificial  silk  are: 

(1)  Pyroxylin  Silk  (Chardonnet  Silk  *) :  made  from  a  solution 
of  nitrated  cellulose  in  a  mixture  of  alcohol  and  ether,  the  cel- 

*Lehner  Silk  is  also  a  pyroxylin  silk  made  by  a  process  somewhat 
different  from  that  of  Chardonnet. 


380  TECHNICAL  METHODS  OF  ANALYSIS 

lulose  being  usually  afterwards  denitrated  with  dil.  HNOs,  Feds 
and  (NH4)2HP04. 

(2)  Cupr ammonium  Silk  (Pauly  Silk) :    made  from  a  solution 
of  cellulose  in  ammoniacal  copper  solution  (or  sometimes  ammonia- 
cal  chloride  of  zinc). 

(3)  Viscose  Silk:    made  from  a  solution  of  alkaline  cellulose 
xanthate  prepared  by  the  action  of  NaOH  and  €82  on  mercerized 
cellulose. 

(4)  Gelatin  Silk:  made  from  gelatin  filaments  rendered  insolu- 
ble by  treating  with  formaldehyde. 

(5)  Acetate  Silk   (Celestron    Silk,   Lustron  Silk):    made  from 
cellulose  acetate. 

A  cold  solution  of  chromic  acid  dissolves  all  artificial  silks, 
whereas  real  silk  dissolves  but  slowly  and  cotton  and  other  vege- 
table fibers  are  unaffected.  KOH  solution  does  not  dissolve  col- 
lodion or  cellulose  silks,  but  in  a  boiling  solution  gelatin  silk  and 
real  silk  are  soluble.  Schweitzer's  reagent  dissolves  collodion 
and  cellulose  silks,  as  well  as  natural  silk,  whereas  gelatin  silk 
is  insoluble  and  stains  the  liquid  bright  violet.  Loew's  reagent 
dissolves  real  silk  immediately  at  80°  C.  It  will  dissolve  Tussah 
and  gelatin  silk  when  boiled  for  one  minute;  other  artificial  silks 
are  not  affected.  The  best  solution  for  separating  real  silk  from 
wool,  cotton,  and  artificial  silk  is  Loew's  reagent. 

The  differentiation  between  the  three  most  common  varieties 
of  artificial  silks,  namely,  Pyroxylin,  Cuprammonium  and  Vis- 
cose silks,  can  be  quickly  made  with  2  reagents,  Fehling's  solu- 
tion and  zinc  chloride-iodine  solution,  as  follows: 

Heat  0.2  gram  of  the  silk  with  2  cc.  of  Fehling's  solution  on 
the  water  bath  for  10  minutes  in  a  test-tube  and  then  fill  the  test 
tube  with  water.  Pyroxylin  silk  produces  a  green  color,  whereas 
the  other  two  give  a  clear  blue.  Furthermore,  on  the  threads  of 
the  pyroxylin  silk  there  will  be  noticeable  a  yellowish  precipitate 
of  cuprous  oxide  or  hydroxide.  The  reaction  depends  upon  the 
different  reducing  powers  of  the  artificial  silks.  Only  in  the  case 
of  the  pyroxylin  silk  (nitrocellulose)  is  the  reducing  power  appreci- 
ably increased. 

To  further  distinguish  between  cuprammonium  and  viscose 
silks,  cover  equal  weights  of  the  silks  in  a  test-tube  with  zinc 
chloride-iodine  solution  and  after  a  few  seconds  pour  off  the  excess 


ANALYSIS  OF  TEXTILES  AND   TEXTILE  FIBERS 

of  the  reagent.  Then  fill  the  test-tube  with  water,  pour  the  water 
off  and  repeat  this  washing  process  until  the  water  is  only  light 
yellow  or  colorless.  Cuprammonium  silk  is  only  weakly  colored 
under  these  conditions  and  loses  the  brown  shade  very  quickly 
when  washed,  whereas  viscose  silk  is  colored  a  bluish-green  and 
retains  the  color  a  longer  time. 

Cellulose  acetate  silk  is  soluble  in  a  mixture  of  5  parts  of  chloro- 
form and  2  parts  of  denatured  alcohol  by  volume.  As  a  confirm- 
atory test  it  may  be  saponified  with  KOH,  forming  potassium 
acetate,  which  in  turn  will  yield  acetic  acid  when  treated  with 
H2SO4. 

Pyroxylin  silk  which  has  not  been  denitrated  can  also  be  saponi- 
fied with  KOH,  forming  KNOs  which  may  be  identified  by  the 
common  qualitative  test  for  nitrates. 

It  is  advisable  in  making  the  above  identity  tests  to  run  com- 
parison tests  with  artificial  silks  of  known  origin. 

REAGENTS. — The  different  reagents  are  made  up  as  follows  : 

(a)  Schweitzer's  Reagent. — Dissolve  5  grams  of  copper  sulfate 
crystals  in  100  cc.  of  boiling  water,  add  NaOH  solution  to  com- 
plete precipitation,  wash  the  precipitate  thoroughly,  and  then 
dissolve  in  the  least  quantity  of  cone.  NKUOH.  This  should  give 
a  deep  blue  solution. 

(6)  Loew's  Reagent. — Dissolve  16  grams  of  copper  sulfate  in 
150  cc.  of  water  and  add  10  grams  of  glycerol.  Then  add  care- 
fully a  solution  of  NaOH  until  the  precipitate  which  at  first  forms 
is  just  re-dissolved. 

(c)  Fehling's  Solution. — The  Fehling's   solution  is  made  by 
mixing  just  before  use  equal  volumes  of  the  Soxhlet  modifications 
of  Fehling's  copper  solution,  and  Fehling's  alkaline  tartrate  solu- 
tion, the  formulas  of  which  are  given  on  page  3. 

(d)  Zinc  Chloride- Iodine    Solution. — Dissolve  2  grams  of  KI 
and  0.1  gram  of  iodine  in  5  cc.  of  water.     Add  to  this  a  solution 
of  20  grams  of  ZnCk  in  10  cc.  of  water.     Let  settle  and  use  the 
clear  solution. 

REFERENCES:  J.  M.  Mathews:  "The  Textile  Fibers";  Wochenblatt 
fur  Papierfabrikation,  November  30th,  1907;  Worden:  "  Nitrocellulose 
Industry,"  Volume  1,  page  560. 


382  TECHNICAL  METHODS  OF  ANALYSIS 

CHEMICAL  TESTS  OF  ROPES  AND  TWINES 

General. — The  chemical  tests  usually  desired  on  ropes  and 
twines  are: 

(1)  Moisture. 

(2)  Ether  extract,  to  show  the  amount  of  oilor  tar. 

(3)  Water  extract,  to  show  whether  the  material  has  been 
treated  with  any  chemicals,  such  as  CaCk  solution. 

(4)  Ash. 

Sampling. — It  is  very  important  to  get  a  representative  sample. 
On  twine  and  small  rope,  samples  should  be  obtained  by  cutting 
pieces  2  or  3  inches  long  from  sufficient  portions  to  represent  the 
whole  sample.  If  the  twine  is  wound  on  a  spindle  or  card,  the 
abnormally  dry  outside  layer  should  be  discarded  and  samples 
taken  from  the  interior.  On  large  ropes  and  cables,  the  material 
should  be  unstranded  and  portions  taken,  not  only  from  each 
strand  but  also  representative  of  the  outside  and  inside  of  the 
twists  in  each  strand.  In  making  the  analysis  it  will  save  cal- 
culation if  an  even  number  of  grams  is  weighed  out. 

Ether  Extract. — Weigh  out  10  grams  and  extract  (preferably 
in  a  straight  extractor)  with  ether  for  ten  to  sixteen  hours.  Dry 
the  extract  to  constant  weight  at  not  over  100°  C. 

Moisture. — Dry  the  residue  from  the  ether  extract  to  constant 
weight  at  100°  C.  and  calculate  the  total  percentage  loss  from  the 
original  weight.  This  loss  will  be  moisture  plus  ether  extract. 
Subtract  from  this  the  ether  extract;  the  difference  will  be  moisture. 

Water  Extract. — Place  the  dried  residue  from  the  ether  extract 
in  a  beaker  and  heat  to  boiling  with  distilled  water.  Decant  the 
water  through  a  filter,  catching  the  filtrate  in  a  liter  volumetric 
flask.  Drain  off  as  much  water  as  possible  and  again  heat  to 
boiling  with  a  fresh  portion  of  distilled  water.  Repeat  this 
5-8  times,  or  until  the  filtrate  is  colorless,  using  about  100  cc.  of 
water  each  time.  Make  up  to  the  mark  with  distilled  water  and 
pipette  out  an  aliquot  of  200  cc.  (representing  2  grams  of  the 
original).  Evaporate  to  dryness  on  the  steam  bath  in  a  weighed 
platinum  dish  and  then  dry  to  constant  weight  in  the  oven  at 
100°  C.  Cool  in  a  desiccator  and  weigh.  Report  the  result  as 
Total  Water-Soluble  Matter. 

Ignite  the  above  residue  at  not  over  dull  red  heat  until  all 


ANALYSIS  OF   TEXTILES  AND   TEXTILE  FIBERS        383 

carbon  is  burnt  off.     Cool  in  a  desiccator  and  weigh.     Report  the 
result  as  Water-Soluble  Mineral  Matter. 

NOTES. — (1)  If  merely  the  total  water-soluble  is  desired,  the  residual  fiber 
after  extracting  may  be  dried  to  constant  weight  at  100°  C.  and  the  loss  to 
water  reported  as  Water-Soluble  Matter. 

(2)  In  case  the  ash  fuses,  let  it  cool,  dissolve  in  hot  water,  filter  through  a 
quantitative  filter,  ignite  the  filter  paper  in  the  weighed  platinum  dish,  then 
add  the  filtrate,  evaporate  to  dryness,  ignite  gently,  cool  in  a  desiccator  and 
weigh. 

Ash  of  Fiber. — If  the  residual  fiber  from  the  water  extract  has 
been  dried  to  constant  weight,  weigh  out  2  grams  quickly  and  ignite 
in  a  weighed  platinum  crucible  to  a  white  ash;  cool  in  a  desiccator 
and  weigh.  Calculate  the  ash  to  the  original  basis. 

If  the  residual  fiber  from  the  water  extract  has  not  been 
dried,  drive  off  the  bulk  of  water  on  the  steam  bath  and  ignite  in 
a  weighed  platinum  crucible,  in  small  portions  at  a  time,  taking 
care  to  avoid  drafts  which  would  blow  any  of  the  light  ash  from 
the  crucible.  (For  the  same  reason  the  fiber  should  not  be  allowed 
to  take  fire  and  burn  but  should  be  smoked  down  to  a  char  before 
raising  the  heat.)  In  this  case,  in  calculating  the  percentage, 
use  the  original  weight  of  10  grams. 

NOTE. — The  ash  thus  obtained  is  the  natural  ash  of  the  fiber.  The  total 
ash  would  be  the  sum  of  this  ash  and  the  water-soluble  mineral  matter. 

Fiber. — The  fiber  is  obtained  "  by  difference."  Add  together 
the  percentages  of  ether  extract,  moisture,  water  soluble  and  ash 
of  the  fiber,  and  subtract  the  sum  from  100%. 

DIFFERENTIATION  OF  ROPE  AND  CORDAGE  FIBERS 

General. — In  this  country  ropes  are  generally  made  from  the 
following  fibers: 

(1)  Manila,  fine  and  coarse. 

(2)  Sisal. 

(a)  Mexican.     This  is  the  most  common  and  cheapest. 

(b)  East  African,  which  is  now  out  of  the  market. 

(c)  Java. 

(d)  Bahama. 

(3)  New  Zealand  flax.     This  is  not  a  true  flax. 


384  TECHNICAL  METHODS  OF  ANALYSIS 

(4)  Mauritius. 

(5)  Tampico  or  Istle. 

(6)  Flax,  hemp  and  jute;  used  for  twines  but  not  much  for  rope. 
Abroad  hemp  is  used  mixed  with  other  fibers.     An  experienced 

eye  can  distinguish  between  manila  and  sisal  but  not,  generally 
speaking,  between  sisal  from  different  sources. 

New  Zealand  flax  may  generally  be  distinguished  under  the 
microscope  by  the  presence  of  fibrillse  which  give  it  a  ragged  ap- 
pearance. 

Istle  or  Tampico  is  distinct  because  the  fiber  is  of  a  horny 
character  and  is  nearly  round  like  a  horse  hair.  The  length  is 
usually  under  2  feet,  much  shorter  than  other  rope  fibers. 

Distinction  between  Sisal  and  Manila. — For  distinguishing 
between  sisal  and  manila,  use  the  Swett  color  reaction  *  with  bleach 
followed  by  NELiOH.  This  test  was  developed  in  this  laboratory 
and  is  as  follows :  Submerge  the  suspended  fibers  in  a  solution  of 
chloride  of  lime  (bleaching  powder)  made  distinctly  acid  with 
acetic  acid.  This  solution  should  contain  3-6%  of  available 
chlorine.  After  the  fibers  have  soaked  for  five  rr.inutes,  remove, 
rinse  with  water  and  immerse  in  NH^OH  (1  :  1).  The  resulting 
color  should  be  examined  at  once,  as  after  five  rrinutes  it  is  likely 
to  change.  Manila  gives  an  umber  brown,  hemp  a  faint  pink, 
and  most  of  the  other  fibers  a  cherry  red.  The  umber  brown 
color  appears  to  be  characteristic  of  manila. 

For  applying  this  test  to  rope,  it  is  advisable  to  remove  the  oil 
with  ether  previous  to  staining. 

Microscopic  Examination. — To  prepare  a  slide  from  a  rope  or 
yarn  for  microscopic  examination,  take  a  strand  and  remove  the 
oil  with  ether.  Then  boil  with  NaOH  solution  (about  5%) 
for  two  or  three  minutes,  rinse,  stain  if  desirable,  and  finally  rinse 
again.  While  the  fibers  are  still  damp  and  relatively  soft,  trim 
the  end  with  a  razor  or  a  sharp  knife.  Then,  resting  the  bundle 
on  a  piece  of  wood,  cut  the  end  across.  The  bundle  usually  sticks 
together  as  a  unit.  The  length  of  the  sections  need  not  be  over 
1  mm.  Separate  these  cut  ends  on  a  slide,  add  a  drop  of  50% 
glycerol  and  press  with  the  flat  side  of  a  knife  blade  to  break  up 
the  fiber  bundles.  Finally  cover  with  a  cover  glass  and  examine 
under  the  microscope,  using  100-300  diameters  magnification. 
*J.  Ind.  Eng.  Chem.  10,  227  (1918). 


ANALYSIS  OF  TEXTILES  AND   TEXTILE  FIBERS       385 

If  spiral  vessels  are  seen,  it  means  that  the  sample  contains  some 
fiber  other  than  manila. 


ASBESTOS  COTTON  TWINE 

General. — In  a  twine  consisting  of  asbestos  and  cotton,  a 
determination  of  the  loss  on  ignition  will  give  an  approximation 
of  the  amount  of  cotton  present,  provided  the  loss  on  ignition  of 
the  asbestos  itself  can  be  ascertained.  As  this  is  not  generally 
possible,  however,  and  since  the  loss  on  ignition  of  asbestos  from 
different  sources  varies  widely,  it  is  generally  necessary  to  deter- 
mine the  cotton  by  dissolving  it  out  with  Schweitzer's  reagent. 
(See  page  381.) 

The  reagent  should  always  be  tested  out  with  absorbent  cotton 
to  see  that  it  works  properly.  The  directions  for  making  up 
should  be  followed  exactly  and  the  final  solution  should  dissolve 
cotton  completely  in  the  cold.  The  solution  readily  decomposes 
and  should  be  made  up  rapidly,  and  only  in  small  quantities  as 
needed. 

Cotton. — Weigh  out  1  gram  of  the  twine  *  and  treat  in  the  cold 
with  Schweitzer's  reagent,  using  at  least  100  cc.  of  the  reagent  per 
gram  of  the  twine.  Let  stand  for  several  hours,  preferably  over- 
night; dilute  to  several  times  its  volume  with  distilled  water  and 
decant  through  linen  cloth  on  a  Buchner  funnel.  (The  best  linen 
for  this  purpose  is  that  used  in  the  determination  of  crude  fiber.) 

Wash  with  warm  water,  and  then  with  cold,  to  remove  the 
copper  clinging  to  the  asbestos  fibers.  Remove  the  residue  from 
the  linen  and  again  digest  with  Schweitzer's  reagent,  washing  as 
before.  Dry  the  fibers  in  a  tared  weighing  bottle,  cool  in  a  des- 
iccator and  weigh  (with  the  bottle  stoppered) .  Repeat  the  process 
of  digestion,  washing  and  weighing  until  the  twine  ceases  to  lose 
weight  upon  further  treatment  with  the  reagent. 

The  loss  to  Schweitzer's  reagent  is  the  cotton  plus  the  free 
moisture,  which  is  determined  on  a  separate  portion  and  sub- 
tracted., 

*  Many  asbestos  cotton  twines  are  reinforced  with  a  brass  or  copper  wire 
This  wire  should  be  removed  before  making  the  analysis  and  the  results 
reported  on  the  twine  itself,  unless  otherwise  instructed. 


386  TECHNICAL  METHODS  OF  ANALYSIS 

NOTE. — If  the  fibers  appear  blue  after  washing  with  cold  water,  the  last 
traces  of  copper  may  be  removed  by  washing  with  an  extremely  dilute  solu- 
tion of  acetic  acid  followed  by.  a  further  washing  with  water  before  drying. 

Moisture. — Determine  the  moisture  on  a  separate  sample  by 
drying  1  gram  to  constant  weight  at  105°  C.  in  a  weighing  bottle. 
As  the  material  is  hygroscopic,  it  must  be  weighed  with  the 
weighing  bottle  stoppered. 

Loss  on  Ignition. — The  dried  sample  from  the  moisture  deter- 
mination may  be  used  for  the  loss  on  ignition,  which  is  conducted 
in  the  usual  way  in  a  platinum  crucible. 

NOTES. — (1)  All  results  should  be  reported  on  the  moisture-free  basis. 
(2)  This  method  is  based  on  analyses  carried  out  in  this  laboratory. 


CHAPTER  X 
ANALYSIS   OF  FOODSTUFFS 

AMMONIA  IN  EGGS 

SET  up  the  apparatus  as  shown  in  Fig.  24.  If  the  eggs 
are  odorless,  weigh  out  about  22  grams.  If  the  odor  is  rather 
strong,  weigh  out  10-12  grams.  In  weighing  out  the  sample  pour 


A  B  C 

FIG.  24. — Apparatus  for  Determining  Ammonia  in  Eggs. 

some  of  the  thoroughly  mixed  eggs  into  a  beaker  and  weigh  the 
two.  Then  pour  the  desired  amount  from  the  beaker  into  the 
tall  cylinder  "  B  "  and  again  weigh  the  beaker  and  contents. 

In  the  250  cc.  graduated  flask  "  C  "  place  about  60  cc.  of  dis- 
tilled water  and  add  1  cc.  of  0.2  N  HC1  or  H2S04.  To  the  eggs 
in  the  cylinder  add  5  cc.  of  a  solution  of  equal  parts  of  a  10% 
solution  of  K2CO3  and  a  15%  solution  of  K^C^.  The  solutions 
of  carbonate  and  of  oxalate  should  be  made  up  separately  and 
mixed  just  before  using. 

387 


388  TECHNICAL  METHODS  OF  ANALYSIS 

After  adding  the  above  solution  to  the  eggs,  pour  in  sufficient 
mineral  oil  (a  heavy  engine  or  machine  oil  is  most  satisfactory) 
to  form  a  layer  about  0.5-0.75  inch  deep  on  the  surface  of  the  eggs. 
This  is  to  prevent  frothing.  Connect  up  the  apparatus  as  shown 
in  the  figure.  The  tube  in  the  bottle  "  A  "  should  dip  below  the 
surface  of  the  H^SCU  to  remove  moisture  and  any  NHs.  In  the 
cylinder  "  B  "  the  inlet  tube  should  reach  nearly  to  the  bottom. 
Connect  the  tube  at  "  E  "  to  an  air  blast  and  blow  a  rapid  current 
of  air  through  the  apparatus  for  at  least  two  hours.  There  should 
be  a  "  trap  "  bottle  between  "  E  "  and  the  blast  to  prevent  the 
blowing  over  of  any  dust  or  other  foreign  matter  into  the  cone. 
H2SO4  in  "  A." 

After  air  has  been  blown  through  the  eggs  for  a  sufficient  length 
of  time  to  carry  over  all  the  NHs,  remove  the  flask  "  C  "  and  make 
the  solution  up  to  250  cc.  Nesslerize  an  aliquot  of  this  solution 
and  compare  it  with  the  regular  Nessler  standards  as  used  in  the 
determination  of  NHs  in  sanitary  water  analysis  (page  500). 
The  aliquot  taken  for  comparison  will  depend  upon  the  amount 
of  NHa  present  in  the  eggs.  It  should  not  develop  a  color  more 
intense  than  that  given  by  5  cc.  of  the  standard  NH4C1 
solution.  • 

The  nesslerization  is  conducted  as  follows :  The  standard  NILtCl 
solution  used  in  sanitary  water  analysis  contains  0.000012  gram 
of  NHs  per  cc.  It  is  made  by  dissolving  3.822  grams  of  c.  P. 
NHiCl  in  1000  cc.  of  ammonia-free  water,  and  diluting  10  cc.  of 
this  solution  to  1000  cc.  with  ammonia-free  water.  The  Nessler 
solution  is  made  by  dissolving  61.75  grams  of  KI  in  250  cc.  of 
distilled  H2O  and  adding  a  saturated  solution  of  HgCl2  cautiously, 
till  a  slight  permanent  red  precipitate  appears.  Dissolve  this 
slight  precipitate  by  adding  0.75  gram  of  powdered  KI.  Then 
add  150  grams  of  KOH  dissolved  in  250  cc.  of  H2O.  Make  up 
to  1  liter  and  settle  overnight. 

Carry  out  the  nesslerization  in  50  cc.  tall  Nessler  tubes.  For 
the  standards  take  0.1,  0.3,  0.5,  0.7,  1.0,  1.5,  2.0,  2.5,  3.0,  3.5,  4.0, 
4.5,  and  5.0  cc.,  respectively,  of  the  above  standard  NELiCl  solu- 
tion, each  in  a  separate  tube.  In  another  tube  place  the  aliquot 
of  the  solution  to  be  tested.  Add  1  cc.  of  the  Nessler  solution  to 
each  tube  and  dilute  to  50  cc.  with  distilled  water.  Mix  thor- 
oughly, let  stand  ten  minutes,  and  match  up  the  sample  with  the 


ANALYSIS  OF  FOODSTUFFS  389 

standard  giving  the  same  color.     Calculate  the  amount  of  NHs 
in  the  original  eggs  in  parts  per  100,000. 

NOTES. — (1)  This  method  was  furnished  by  H.  C.  Lythgoe,  Chemist  of 
the  Mass.  Board  of  Health,  and  has  been  used  in  our  laboratory  with  suc- 
cess for  several  years. 

(2)  The  Nessler  solution  described  on  page  499  may  be  used  in  place  of  the 
one  above  described. 

(3)  The  amount  of  NH3  in  fresh  eggs  varies  with  the  fat  content.     The 
ratio  of  NH3  (expressed  as  parts  per  100,000)  to  fat  (expressed  as  percentage) 
should  be  about  1  I  2.5.     In  other  words,  for  fresh  eggs  the  NH3  should  not 
be  over  4  parts  when  the  fat  is  10%,  and  not  over  8  parts  when  the  fat  is 
20%.     (The  fat  may  be  determined  by  drying  the  egg  material  in  a  Hof- 
meister  Schaelchen  and  extracting  with  anhydrous  ether.) 


COLORING  MATTER  IN  FOODS 

General. — The  following  procedures  are  the  tentative  methods 
of  the  Association  of  Official  Agricultural  Chemists  published  in 
its  Journal,  Vol.  II,  Methods  of  Analysis  (1916),  page  155. 

Coloring  matters  may  be  divided  into  two  classes:  (1)  Insoluble 
Pigments  and  (2)  Soluble  Dyes  and  their  Lakes. 

(1)  PIGMENTS 

The  insoluble  pigments,  ultramarine,  lampblack,  etc.,  are  most 
commonly  used  as  facings  and  may  be  separated  by  washing  the 
sample  with  water  and  letting  the  washings  settle.  The  par- 
ticles of  coloring  matter  can  be  identified  by  microscdpic  exam- 
ination and  by  chemical  tests  of  the  residue  or  purified  coloring 
matter.*  Most  of  the  common  pigments  other  than  lakes,  such 
as  the  yellow,  brown  and  red  ochers  and  umbers,  are  derivatives  of 
the  heavy  metals  and  contain  Fe,  Mn,  etc.  Others,  such  as  vari- 
ous green  and  blue  compounds,  including  the  green  chlorophyll 
derivatives,  contain  Cu. 

(2)  SOLUBLE  COLORING  MATTERS  AND  THEIR  LAKES 

(I)  Coal-tar  Dyes. — (A)  WOOL  DYEING  TEST. 
(a)  Wines,  fruit  juices,  distilled  liquors,  flavoring  extracts,  vinegars, 
beers,  syrups,  non-alcoholic  beverages  and  similar  products. — Dilute 
*  See  also  Schultz:  "  Farbenstofftabellen,"  5th  German  Ed.,  1911-14. 


390  TECHNICAL  METHODS  OF  ANALYSIS 

20-200  cc.  of  the  sample  with  1-3  volumes  of  water  and  boil,  or 
heat  on  the  steam  bath,  with  a  small  piece  of  white  woolen  cloth 
(nun's  veiling).  When  the  mixture  contains  much  alcohol,  heat 
until  most  of  the  alcohol  has  been  removed;  in  other  cases,  take  out 
the  wool  after  five  to  fifteen  minutes  and  rinse  with  water.  Then 
treat  the  liquid  with  3-4  drops  of  cone.  HC1  for  each  100  cc.  and 
warm  again  for  ten  to  twenty  minutes  with  a  clean  piece  of  wool. 
The  basic  dyes  go  on  the  fiber  best  from  neutral  or  faintly  ammoni- 
acal  solutions  and,  if  present,  will  appear  on  the  first  piece  of  wool. 
Acid  colors  dye  from  neutral  solutions,  but  more  readily  from  those 
containing  free  acid.  If  the  wool  takes  up  any  considerable 
amount  of  coloring  matter  in  either  case,  the  presence  of  coal-tar 
dyes  is  indicated.  The  lichen  colors  (Archil,  Cudbear,  Litmus) 
go  readily  on  wool,  however,  and  many  other  natural  colors,  such 
as  Turmeric,  will  dye  the  fiber,  if  present  in  considerable  amount. 
On  the  other  hand,  a  few  coal-tar  dyes,  especially  Auramine  O 
and  Naphthol  Green  B,  are  quite  unstable  and,  if  present  in  small 
amounts,  may  give  no  distinct  dyeing. 

Acid  dyes  are  much  more  frequently  used  than  basic  dyes  and 
in  most  cases  may  be  removed  from  wool  without  much  decom- 
position by  "  stripping  "  the  latter  with  dil.  NIUOH.  By  the 
action  of  the  alkali  many  natural  colors  are  destroyed,  while 
others  remain  for  the  most  part  on  the  fiber.  If  the  behavior 
with  wool  in  neutral  and  acid  solutions  indicates  the  presence  of 
acid  dyes,  rinse  the  colored  cloth  thoroughly  with  water,  cover 
with  2%  NH40H  in  a  casserole,  boil  for  a  few  minutes,  remove  the 
cloth  and  squeeze  out  the  adhering  liquid.  Boil  the  ammoniacal 
solution  to  remove  excess  of  NHs,  drop  in  a  piece  of  clean,  wet  wool, 
make  distinctly  but  not  strongly  acid  with  HC1  and  boil  again. 
If  acid  coal-tar  dyes  are  present,  they  will  usually  give  a  fairly 
clean,  bright  dyeing  on  the  second  piece  of  wool.  A  further  puri- 
fication may  be  carried  out  by  repeating  the  stripping  and  redye- 
ing,  though  generally  accompanied  by  corresponding  loss  of  dye. 

(b)  Candies  and  similar  colored  sugar  products. — Dissolve  about 
20  grams  of  sample  in  100  cc.  of  water  and  treat  the  solution  as 
directed  under  (a).     When  the  coloring  matter  is  on  the  surface 
of  the  candy,  pour  off  the  solution  before  the  colorless  inner  portion 
has  dissolved. 

(c)  Jams  and  jellies. — Boil  a  mixture  of  10-20  grams  of  the 


ANALYSIS  OF  FOODSTUFFS  391 

sample  and  100  cc.  of  water  with  wool  in  neutral  and  also  in  acid 
solution  as  directed  under  (a).  For  thick  jams  it  is  usually 
better,  though  less  easy,  to  first  extract  the  coloring  substances 
by  treating  the  product  as  directed  below  under  (d). 

(d)  Canned  and  preserved  fruits  and  vegetables,  sausage  casings, 
smoked  fish,  coffee,  spices,  etc. — Macerate  20-200  grams  of  sample 
with  4^5  times  its  weight  of  80%  alcohol.     After  standing  a  few 
hours  pour  off  the  solvent  as  completely  as  possible  and  repeat 
the  extraction,  using  70%  alcohol  containing  about  1%  of  NH.3. 
(1)  Examine  separately  the  filtered  alcoholic  extracts  as  directed 
under  (a);   or,  (2)  boil  the  ammoniacal  solution  until  practically 
neutral,  complete  the  neutralization  with  acetic  acid,  add  the 
neutral  80%  alcohol  extract,  continue  the  evaporation  until  most 
of  the  alcohol  is  removed,  and  boil  with  wool  as  directed  under  (a). 

(e)  Cocoa  and   chocolate   products. — Treat   cocoa   as   directed 
under  (d).     The  alcoholic  extract  will  contain  a  large  amount  of 
natural  coloring  matter  and  several  dyeings  and  strippings  may 
be  necessary  to  get  rid  of  this  in  order  to  show  the  presence  of 
coal-tar  dyes. 

Chocolate  may  be  treated  similarly  but  the  following  procedure 
is  preferable:  Wash  20-200  grams  of  the  well-divided  sample 
with  gasoline  on  a  filter  until  most  of  the  fat  has  been  removed; 
if  the  gasoline  is  colored,  reserve  for  the  examination  of  oil-soluble 
dyes  as  directed  below  under  Oil-Soluble  Dyes.  Remove  most  of 
the  adherent  solvent  from  the  residue  by  evaporation  or  pressure 
between  layers  of  absorbent  paper  and  digest  with  alcohol  as 
directed  under  (d). 

Coal-tar  dyes  may  also  be  detected  in  chocolate  and  cocoa 
products  by  mixing  directly  with  3^  times  their  weight  of  hot 
water  and  immediately  boiling  the  magma  with  wool,  as  directed 
under  (a).  Because  of  the  presence  of  large  amounts  of  fatty 
and  protein  materials,  this  method  is  not  very  satisfactory. 

(/)  Cereal  products. — Proceed  as  directed  under  (d),  in  most 
cases  working  with  a  large  amount  of  the  sample,  200-300  grams, 
and  a  relatively  smaller  amount  of  alcohol.  Where  tests  are  to  be 
made  only  for  the  acid  dyes,  the  extraction  with  neutral  80% 
alcohol  may  be  omitted  advantageously. 

(II)  Oil-Soluble  Dyes. — Prepare  an  alcoholic  solution  of  the  oil- 
soluble  dye  by  one  of  the  following  methods  which  are  to  be 


392  TECHNICAL  METHODS  OF  ANALYSIS 

applied  to  the  oil  or  fat  obtained  by  extraction  with  ether  or  gaso- 
line if  the  nature  of  the  substance  requires  it : 

(a)  Shake  the  oil  or  melted  fat  with  an  equal  volume  of  90% 
alcohol.  The  alcohol  after  separation  will  contain  Aniline  Yellow, 
Butter  Yellow,  Aminoazotoluene  and  Auramine,  if  present. 

(6)  Saponify  20-200  grams  of  the  oil  or  fat  with  alcoholic  KOH 
and,  after  removal  of  most  of  the  alcohol  on  the  steam  bath,  extract 
the  soap  with  ether  or  gasoline.  Most  of  the  common  dyes 
are  removed  by  this  treatment,  though  the  digestion  with  strong 
alkali  may  cause  some  decomposition  and  make  the  extraction 
rather  troublesome. 

(c)  Dilute  20-200  grams  of  the  oil  or  melted  fat  with  1-2  vol- 
umes of  gasoline  and  shake  out  successively  with  2-4%  KOH  or 
NaOH  solution,  12-15%  HC1,  and  phosphoric-sulfuric  acid  mix- 
ture, prepared  by  mixing  85%  HsPC^  with  about  10-20%  by 
volume  of  cone.  H^SC^. 

The  dil.  alkali  extracts  Sudan  G  and  Annatto.  The  dil.  HC1 
extracts  Aniline  Yellow  (7)*,  Aminoazotoluene,  and  Butter 
Yellow  (16)  the  first  two  forming  orange-red,  the  latter  a  cherry- 
red  solution  in  this  solvent.  Benzeneazobetanaphthylamine  and 
homologues  also  come  in  this  group,  though  they  are  not  extracted 
very  readily  and  decompose  rapidly  on  standing  in  strongly  acid 
solution.  The  HsPC^  mixture  is  necessary  for  the  extraction  of 
Sudan  I  (11),  Sudan  II  (49),  and  Sudan  III  (143),  and  the  homo- 
logue  of  the  last,  Sudan  IV.  The  procedure  is  not  very  suitable 
in  the  presence  of  Auramine,  but  this  dye  is  seldom  found  in  oils. 
Neutralize  the  alkaline  and  dil.  HC1  solutions;  dilute  the  H3PO4 
mixture  and  partially  neutralize,  cooling  the  liquid  during  this 
operation;  and  extract  the  dyes  by  shaking  with  ether  or  gasoline. 

For  the  direct  dyeing  test  use  the  alcoholic  solution  obtained 
as  directed  in  (a).  Evaporate  to  dryness  the  ether  or  gasoline 
solutions,  obtained  as  directed  in  (6)  and  (c)  and  dissolve  the 
residue  in  10-20  cc.  of  strong  alcohol.  Add  some  strands  of 
white  silk  and  a  little  water  and  evaporate  on  the  steam  bath  until 
the  alcohol  has  been  removed  or  until  the  dye  is  taken  up  by  the 

*  The  numbers  following  the  names  of  the  dyes  in  parenthesis  are  the 
numbers  by  which  that  dye  is  designated  in  "  A  Systematic  Survey  of  the 
Organic  Coloring  Matters,"  1904,  by  A.  Green,  translated  from  Schultz  and 
Julius. 


ANALYSIS  OF  FOODSTUFFS  393 

silk.  The  dyeing  test  is  sometimes  unsatisfactory  and  in  all  cases 
a  small  portion  of  the  alcoholic  solution  should  be  tested  by  treat- 
ment with  an  equal  volume  of  cone.  HC1  and  SnCl2  solution, 
respectively.  The  common  oil-soluble  coal-tar  dyes  are  rendered 
more  red  or  blue  by  the  acid  and  are  decolorized  by  the  reducing 
agent.  Most  of  the  natural  coloring  matters  become  slightly 
paler  with  the  acid  and  are  little  changed  by  the  SnCl2  solution. 

NOTE. — For  the  separation  and  identification  of  the  permitted  coal  tar 
colors,  see  J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis  (1916);  also 
U.  S.  Dept.  of  Agr.,  Bureau  of  Animal  Industry,  Circular  180  (July,  1911), 
and  J.  Ind.  Eng.  Chem.  8,  1123  (1916), 

CRUDE  FIBER 

General. — The  official  method  for  determination  of  crude 
fiber  as  directed  by  the  U.  S.  Dept  of  Agriculture,  Bur.  of  Chem., 
Bulletin  107,  page  56,  is  a  long  and  tedious  process.  It  has  been 
somewhat  modified  by  M.  O.  Sweeney  (Bulletin  137,  page  157), 
so  that  the  time  consumed  is  considerably  shortened.  It  has  been 
claimed,  however,  that  for  certain  kinds  of  feed-stuffs,  especially 
those  rich  in  protein,  the  Sweeney  method  is  not  entirely  satis- 
factory. This  has,  therefore,  been  further  modified  by  Cornelia 
Kennedy  [J.  Ind.  Eng.  Chem.,  4,  600  (1912)].  The  three  methods 
are  given  below,  but,  except  for  special  cases,  the  Kennedy 
modification  is  the  one  to  be  employed  in  routine  work. 

Official  Method.* — Prepare  solutions  of  H2SO4  and  of  NaOH. 
each  of  exactly  1.25%  strength,  as  determined  by  titration. 

Extract  a  quantity  of  the  sample  representing  about  2  grams 
of  the  dry  material  with  ordinary  ether  (or,  in  case  the  oil  in  the 
sample  has  been  determined,  use  the  residue  from  that  deter- 
mination). To  the  extracted  residue  in  a  500  cc.  flask  add  200  cc. 
of  boiling  1.25%  H^SC^.  Connect  the  flask  with  an  inverted 
condenser,  the  tube  of  which  passes  only  a  short  distance  beyond 
the  rubber  stopper  into  the  flask,  or,  if  a  tall  conical  flask  is  used, 
simply  cover  with  a  watch  glass  or  short-stem  funnel,  boil  at  once 
and  continue  boiling  gently  for  thirty  minutes.  A  blast  of  air 
conducted  into  the  flask  will  reduce  the  frothing  of  the  liquor. 
Filter  through  linen,  and  wash  with  boiling  water  until  the  wash- 

*  J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis  (1916),  page  118. 


394  TECHNICAL  METHODS  OF  ANALYSIS 

ings  are  no  longer  acid.  Rinse  the  residue  back  into  the  flask 
with  200  cc.  of  a  boiling  1.25%  solution  of  NaOH,  which  should  be 
free,  or  nearly  so,  from  carbonate.  Boil  at  once  and  continue 
boiling  gently  for  thirty  minutes,  in  the  same  manner  as  directed 
above  for  the  treatment  with  acid.  Filter  at  once  rapidly.  (A 
Gooch  crucible  will  be  found  convenient.)  Wash  with  boiling 
water  until  the  washings  are  neutral.  Dry  at  110°  C.  until  it 
ceases  to  lose  weight.  Weigh,  incinerate  completely  and  weigh 
again.  The  loss  of  weight  is  considered  to  be  crude  fiber. 

NOTE. — If  filtration  proceeds  very  slowly  through  a  Gooch  crucible,  the  last 
filtration  may  be  made  through  linen  or  a  tared  filter  paper.  If  a  linen  filter 
is  used,  rinse  the  crude  fiber,  after  washing  is  completed,  into  a  flat-bottomed 
platinum  dish  by  means  of  a  jet  of  water;  evaporate  to  dryness  on  a  steam 
bath,  dry  to  constant  weight  at  110°  C.,  weigh,  incinerate  completely  and 
weigh  again.  The  loss  in  weight  is  considered  to  be  crude  fiber. 

If  a  tared  filter  paper  is  used,  weigh  in  a  weighing  bottle.  In  any  case 
the  crude  fiber  after  drying  to  constant  weight  at  110°  C.  must  be  inciner- 
ated and  the  amount  of  ash  deducted  from  the  original  weight. 

Sweeney  Modification. — Place  2  grams  of  the  oil-free  material 
in  a  wide-mouth  Erlenmeyer  flask  of  liter  size,  inserting  a  small  air 
condenser  in  the  mouth  of  the  flask  to  prevent  concentration  due  to 
loss  of  steam.  To  the  sample  in  the  flask  add  200  cc.  of  a  boiling 
1.25%  solution  of  H2SO4,  as  in  the  Official  Method.  Heat  to 
boiling  and  after  gently  boiling  for  thirty  minutes  treat  as  follows : 

Neutralize  with  a  10%  solution  of  NaOH,  using  a  few  drops 
of  phenolphthalein  as  indicator.  Approximately  25  cc.  of  NaOH 
solution  are  required.  Add  at  once  200  cc.  of  a  boiling  2.656% 
solution  of  NaOH.  This  solution  should  be  prepared  as 
accurately  as  possible  by  titration.  Continue  the  digestion  at 
the  boiling  point  for  thirty  minutes  longer  in  the  same  manner  as 
in  the  treatment  with  acid.  Then  filter  the  alkaline  solution  con- 
taining the  fiber  residue  rapidly  through  a  linen  cloth  and  wash 
repeatedly  with  boiling  water.  Transfer  the  fiber  residue  to  a 
weighed  platinum  Gooch  crucible  and  wash  with  alcohol  and 
finally  with  ether.  Dry  at  100°  C.  to  constant  weight.  Ignite 
the  dried  residue  and  again  weigh.  The  loss  in  weight  gives  the 
weight  of  crude  fiber. 

Kennedy  Modification. — Digest  2  grams  of  the  fat-free  sample 
with  200  cc.  of  a  1.25%  H2SO4  solution  by  boiling  thirty  minutes  in 


ANALYSIS  OF  FOODSTUFFS  395 

a  liter  Erlenmeyer  flask  connected  to  an  air  condenser  exactly  as 
in  the  Sweeney  Modification.  Then  add  directly  200  cc.  of  a 
3.52%  solution  of  NaOH,  the  solution  being  made  of  this  exact 
strength  by  titration.  Boil  the  whole  for  thirty  minutes,  filter 
through  linen  and  wash  free  from  alkali  with  hot  water.  Then 
wash  thoroughly  with  boiling  1.25%  H2SO4  which  will  remove  any 
material  precipitated  by  the  addition  of  the  alkali.  Wash  free 
from  acid.  Transfer  from  the  linen  filter  to  a  weighed  Gooch 
crucible,  wash  with  alcohol,  then  with  ether,  and  dry  to  constant 
weight  at  100°  C.  Weigh  the  residue,  ignite  and  reweigh.  The 
loss  indicates  the  amount  of  crude  fiber. 

SULFUR  DIOXIDE  IN  FOODSTUFFS 

General. — Free  sulfurous  acid  in  the  form  of  sulfur  fumes  is 
extensively  employed  to  bleach  molasses,  disinfect  wine  casks  and 
to  bleach  and  preserve  dried  fruits.  The  process  is  known  as 
"  sulfuring."  The  sulfurous  acid  salts  most  commonly  employed 
as  preservatives  are  the  bisulfites  of  Na  and  of  Ca.  The  normal 
sulfites  (Na,  K  or  NHi)  are  most  commonly  used  as  preservatives 
in  fruit  juices,  ketchup,  fruit  and  vegetable  pulp,  wines,  malt 
liquors  and  meat  products.  They  are  frequently  mixed  with 
other  antiseptics,  such  as  salicylates  and  benzoates. 

Determination. — The  same  methods  are  used  for  the  qualitative 
detection  of  862  as  for  its  quantitative  determination,  except  that 
in  the  former  case  weighed  quantities  need  not  be  employed. 

(A)  DISTILLATION  METHOD. — This  method  is  adapted  to  all 
food  products  whether  solid  or  liquid. 

Place  50-200  grams  of  the  material  in  a  500  cc.  flask,  add  water, 
if  necessary,  and  5  cc.  of  a  20%  solution  of  HaPC^,  and  distill  in  a 
current  of  CO2  into  about  100  cc.  of  water  containing  a  few  drops 
of  bromine,  until  150  cc.  have  passed  over.  If  sulfides  are  present, 
as  is  true  of  decomposed  meat  products  and  possibly  other  foods, 
the  steam  from  the  distilling  flask  before  entering  the  condenser 
should  be  passed  through  a  flask  containing  40  cc.  of  a  2%  neutral 
solution  of  CdCl2  or  a  1%  solution  of  CuSCX.  These  solutions 
effectually  remove  the  H^S  without  retaining  any  appreciable 
amount  of  862.  To  avoid  escape  of  862,  the  condenser  tube 
should  dip  below  the  surface  of  the  bromine  solution. 


396  TECHNICAL  METHODS  OF  ANALYSIS 

The  method  and  apparatus  may  be  simplified  without  material 
loss  in  accuracy  by  omitting  the  current  of  CO2,  adding  10  cc.  of 
HsPC^  instead  of  5  cc.,  and  dropping  into  the  distilling  flask  a  piece 
of  NaHCOs,  weighing  not  more  than  a  gram,  immediately  before 
attaching  the  condenser. 

When  the  distillation  is  finished,  boil  off  the  excess  of  Br, 
dilute  to  about  250  cc.,  add  1  cc.  of  cone.  HC1,  heat  to  boiling  and 
add,  drop  by  drop,  while  boiling,  an  excess  of  BaCl2  solution.  Let 
stand  overnight  in  a  warm  place,  filter,  wash  with  hot  water, 
ignite  at  a  dull  red  heat  and  weigh  as  BaS04.  Calculate  to  862 
and  report  as  parts  per  million. 

CALCULATION.— BaSO4  X  0.2744  =  SO2. 

(B)  DIRECT  TITRATION  METHOD. — This  method  is  applicable 
to  Sauternes  and  other  white  wines  and  to  beer,  but  should  not  be 
used  for  other  materials  unless  found  by  experiment  to  yield 
accurate  results. 

To  25  grams  of  the  sample  (finely  divided  in  water,  if  solid  or 
semi-solid)  in  a  200  cc.  flask,  add  25  cc.  of  a  N  solution  of  KOH; 
shake  thoroughly  and  set  aside  for  at  least  fifteen  minutes,  with 
occasional  shaking;  and  then  add  10  cc.  of  H2S04  (!•:  3)  with  a 
little  starch  solution  and  titrate  the  mixture  with  0.02  N  iodine 
solution,  introducing  the  latter  quite  rapidly,  until  a  fixed  blue 
color  is  produced. 

CALCULATION.— 1  cc.  0.02  N  iodine  =  0.00064  gram  of  S02. 

REFERENCE. — Leach:  "  Food  Inspection  and  Analysis"  (1913  edition), 
page  840.  J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis  (1916), 
page  150. 

REDUCING  SUGARS  AND  SUCROSE 

General. — This  method  describes  general  procedures  to  be  used 
in  determining  sucrose  and  different  kinds  of  reducing  sugars  in 
various  materials.  In  employing  these  methods,  however,  the 
analyst  should  make  sure  that  there  are  not  special  methods  or 
precautions  to  be  used  with  the  particular  substances  under 
analysis. 

The  methods  described  below  are  official  methods  of  the 
Association  of  Official  Agricultural  Chemists,  unless  otherwise 
designated. 


ANALYSIS  OF  FOODSTUFFS  397 

(I)  SUCROSE 

There  are  two  general  classes  of  methods  for  the  determination 
of  sucrose:  (1)  Optical  methods,  and  (2)  Chemical  methods. 

(1)  Optical  Methods. — The  rules  of  the  International  Commis- 
sion for  Unifying  Methods  of  Sugar  Analysis  have  been  adopted 
as  a  tentative  method  of  the  Assoc.  Official  Agr.  Chemists  for 
raw  sugars  as  follows: 

(A)  GENERAL  DIRECTIONS  FOR  RAW  SUGARS. — "  In  general,  all 
polarizations  are  to  be  made  at  20°  C.  The  verification  of  the 
saccharimeter  must  also  be  made  at  20°  C.  For  instruments 
using  the  Ventzke  scale  26  grams  of  pure  dry  sucrose,  weighed 
in  air  with  brass  weights,  dissolved  in  100  metric  cc.  at  20°  C. 
and  polarized  in  a  room,  the  temperature  of  which  is  also  20°  C., 
must  give  a  saccharimeter  reading  of  exactly  100.00.  The  tem- 
perature of  the  sugar  solution  during  polarization  must  be  kept 
constant  at  20°  C. 

"  For  countries  where  the  mean  temperature  is  higher  than 
20°  C.,  saccharimeters  may  be  adjusted  at  30°  C.  or  any  other 
suitable  temperature,  under  conditions  specified  above,  provided 
that  the  sugar  solution  be  made  up  to  volume  and  polarized  at 
this  same  temperature. 

"  In  effecting  the  polarization  of  substances  containing  sugar 
employ  only  half -shade  instruments."  The  saccharimeter  used 
may  be  either  single  or  double  wedge  and  should  be  a  half -shadow 
instrument  with  either  double  or  triple  field. 

"  During  the  observation  keep  the  apparatus  in  a  fixed  position 
and  so  far  removed  from  the  source  of  light  that  the  polarizing 
Nicol  is  not  warmed.  As  sources  of  light  employ  lamps  which 
give  a  strong  illumination,  such  as  triple  gas  burner  with'  metallic 
cylinder,  lens  and  reflector;  gas  lamp  with  Auer  (Welsbach) 
burner;  electric  lamp;  petroleum  duplex  lamp;  sodium  light." 
Whenever  there  is  any  irregularity  in  the  sources  of  light,  such  as 
that  due  to  the  convolutions  of  the  filament  in  the  case  of  an 
electric  light  or  to  the  meshes  of  the  gauze  in  the  case  of  the  Wels- 
bach light,  place  a  thin  ground-glass  plate  between  the  source  of 
light  and  the  polariscope,  so  as  to  render  the  illumination  uniform. 

"  Before  and  after  each  set  of  observations  the  chemist  must 
satisfy  himself  of  the  correct  adjustment  of  his  saccharimeter  by 


398  TECHNICAL  METHODS  OF  ANALYSIS 

means  of  standardized  quartz  plates.  He  must  also  previously 
satisfy  himself  of  the  accuracy  of  his  weights,  polarization  flasks, 
observation  tubes  and  cover-glasses.  (Scratched  cover-glasses 
must  not  be  used.)  Make  several  readings  and  take  the  mean 
thereof,  but  no  one  reading  may  be  neglected."  Such  plates 
are  standardized  to  read  to  the  second  decimal  point  and  by  their 
use  a  quick  and  at  the  same  time  accurate  test  can  be  made.  In 
using  such  plates  for  testing  saccharimeters,  it  is  necessary  that 
the  instrument,  as  well  as  the  plate,  be  at  20°  C.,  before  making  a 
reading.  Different  points  of  the  scale,  preferably  20°,  50°,  80°, 
and  100°  (sugar  scale)  should  be  tested  against  the  plates. 

"  In  making  a  polarization  use  the  whole  normal  weight  for 
100  cc.  or  a  multiple  thereof  for  any  corresponding  volume. 

"  As  clarifying  and  decolorizing  agents  use  either  basic  acetate 
of  lead,  alumina  cream,  or  concentrated  solution  of  alum.  Bone 
black  and  decolorizing  powders  are  to  be  excluded."  Whenever 
reducing  sugars  are  determined  in  the  solution  for  polarizing,  use  only 
neutral  lead  acetate  for  clarification,  as  basic  lead  acetate  causes 
precipitation  of  some  of  the  reducing  sugars.  In  addition  to  these 
clarifying  agents  neutral  lead  acetate  and  basic  lead  nitrate 
(Herles'  solution)  have  been  made  official  by  the  Association. 

"  After  bringing  the  solution  exactly  to  the  mark  at  the  proper 
temperature,  and  after  wiping  out  the  neck  of  the  flask  with  filter 
paper,  pour  all  of  the  well-shaken  clarified  (sugar)  solution  on  a 
rapidly  acting  filter.  Reject  the  first  portions  of  the  filtrate, 
and  use  the  rest,  which  must  be  perfectly  clear,  for  polarization." 
It  is  advisable  to  reject  the  first  20  cc.  that  run  through,  then 
cover  the  funnel  with  a  watch  glass  and  use  the  remainder  for 
polarization.  In  no  case  should  the  whole  solution  or  any  part 
be  returned  to  the  filter.  If  cloudy  after  the  20  cc.  have  been 
rejected,  begin  a  new  determination. 

"  Whenever  white  light  is  used  in  polarimetric  determinations, 
the  same  must  be  filtered  through  a  solution  of  potassium  bichro- 
mate of  such  a  concentration  that  the  percentage  content  of  the 
solution  multiplied  by  the  length  of  the  column  of  the  solution  in 
centimeters  is  equal  to  nine."  This  concentration  must  be  doubled 
in  reading  carbohydrate  materials  of  high  rotation  dispersion, 
such  as  commercial  glucose,  etc. 

(B)  PREPARATION  AND  USE  OF  CLARIFYING  REAGENTS  (TEN- 


ANALYSIS  OF  FOODSTUFFS  399 

TATIVE). — (a)  Basic  lead  acetate  solution. — Boil  430  grams  of  neu- 
tral lead  acetate,  130  grams  of  litharge,  and  1  liter  of  water  for 
thirty  minutes.  Let  the  mixture  cool  and  settle,  and  dilute  the 
supernatant  liquid  to  sp.  gr.  1.25  with  recently  boiled  water. 
Solid  basic  lead  acetate  may  be  substituted  for  the  normal  salt 
and  litharge  in  the  preparation  of  the  solution. 

(6)  Alumina  cream. — Prepare  a  cold  saturated  solution  of 
alum  (potassium  aluminum  sulfate)  in  water.  Add  NH40H  with 
constant  stirring  until  the  solution  is  alkaline  to  litmus;  let  the 
precipitate  settle  and  wash  by  decantation  with  water  until  the 
wash  water  gives  only  a  slight  test  for  sulfates  with  BaCk  solution. 
Pour  off  the  excess  of  water  and  store  the  residual  cream  in  a 
stoppered  bottle. 

(c)  Dry    basic    lead    acetate  (Horne   Method). — This    clarify- 
ing agent  is  obtained  as  a  dry  powdered  salt  and  should  con- 
tain   72.8%    of    Pb,    which    corresponds    to    a    composition    of 
3Pb (C2H302)2  •  2PbO.     Dissolve  the  normal  or  half-normal  weight 
of  the  sugar  solution  in  a  flask  with  water  and  complete  the  vol- 
ume.    Add  a  small  quantity  of  the  dry  salt  and  shake,  then  add 
more  and  shake  again,  repeating  until  completely  precipitated, 
but  avoiding  any  excess.     Of  this  salt  0.1346  gram  is  equivalent 
to  1  cc.  of  the  basic  lead  acetate  solution,  described  under  (a). 
When  molasses  or  any  other  substances  producing  a  heavy  pre- 
cipitate is  being  clarified,  some  dry,  coarse  sand  should  be  added 
to  break  up  the  balls  of  basic  lead  acetate  and  the  precipitate. 
(This  method  is  to  have  equal  weight  with  the  use  of  a  solution  of 
basic  lead  acetate  in  clarifying  cane,  sorghum,  and  beet  products.) 

(d)  Neutral  lead  acetate. — Prepare  a  saturated  solution  of  neu- 
tral lead  acetate  and  add  it  to  the  sugar  solution  before  completing 
to  volume.     Its  use  is  imperative  when  determining  the  reducing 
sugars  in  the  solution  used  for  polarization. 

(e)  Basic    lead   nitrate   (Herks'    Solution).- — (1)  Dissolve  250 
grams  of  Pb(NOs)2  in  water  and  make  up  to  500  cc.  (2)  Dissolve 
25  grams  of  NaOH  in  water  and  make  up  to  500  cc.     Add  equal 
amounts  of  (1)  and  (2)  to  the  sugar  solution,  shake,  and  add  more 
if  complete  precipitation  has  not  occurred,  but  avoid  any  excess. 
Then  complete  the  volume  with  water.     When  this  solution  is 
used  for  clarification,   the  factor  in  the  Clerget  determination 
becomes  143.5  instead  of  142.66. 


400  TECHNICAL  METHODS  OF  ANALYSIS 

(C)  DETERMINATION  OF  SUCROSE  IN  THE  ABSENCE  OF  RAF- 
FINOSE  BY  POLARIZATION  BEFORE  AND  AFTER  INVERSION  WITH 
HCL.  * — Dissolve  the  normal  weight  (26  grams)  of  the  substance 
in  water,  add  basic  lead  acetate  carefully,  avoiding  any  excess, 
then  1-2  cc.  of  alumina  cream,  shake  and  dilute  to  100  cc.,  filter, 
rejecting  the  first  20  cc.  of  the  filtrate,  cover  the  filtrate  with  a 
watch  glass  and,  when  sufficient  filtrate  is  collected,  polarize 
in  a  200  mm.  tube.  The  reading  so  obtained  is  the  direct  reading 
(P  of  the  formula  given  below)  or  polarization  before  inversion. 
For  the  invert  reading,  remove  the  Pb  from  the  solution  either  (1) 
by  adding  anhydrous  K2C204,  a  little  at  a  time,  to  the  remaining 
solution,  avoiding  an  excess,  and  removing  the  precipitate  by 
filtration;  or  (2)  by  adding  anhydrous  Na2CC>3  under  the  same 
conditions.  Introduce  50  cc.  of  the  lead-free  filtrate  into  a  100  cc. 
flask  (if  Na2COa  was  used  for  removing  the  Pb,  neutralize  carefully 
the  excess  with  a  few  drops  of  dil.  HC1)  and  add  25  cc.  of  water. 
Then  add,  little  by  little,  while  rotating  the  flask,  5  cc.  of  cone. 
HCL  Heat  the  flask,  after  mixing,  in  a  water  bath  kept  at  70°  C. 
The  temperature  of  the  solution  in  the  flask  should  reach  67- 
69°  C.  in  two  and  one-half  to  three  minutes.  Maintain  a  tem- 
perature of  as  nearly  69°  C.  as  possible  for  seven  to  seven  and  one- 
half  minutes,  making  the  total  time  of  heating  ten  minutes. 
Remove  the  flask,  cool  contents  rapidly  to  20°  C.,  and  dilute  to 
100  cc.  Polarize  this  solution  in  a  tube  provided  with  a  lateral 
branch  and  water  jacket,  keeping  at  20°  C.  This  reading  must  be 
.doubled  to  obtain  the  invert  reading.  If  necessary  to  work  at  a 
temperature  other  than  20°  C.,  which  is  allowable  within  narrow 
limits,  the  volumes  must  be  completed  and  both  direct  and  invert 
polarizations  must  be  made  at  exactly  the  same  temperature. 

The  inversion  may  also  be  accomplished  as  follows:  (1)  To 
50  cc.  of  the  clarified  solution,  freed  from  Pb,  add  5  cc.  of  cone. 
HC1  and  set  aside  for  twenty-four  hours  at  a  temperature  not 
below  20°  C.;  or,  (2)  if  the  temperature  be  above  25°  C.  set  aside 
for  ten  hours.  Make  up  to  100  cc.  at  20°  C.  and  polarize  as 
directed  above. 

Calculate  the  sucrose  by  one  of  the  following  formulas 
(Clerget): 

*  In  the  presence  of  much  levulose,  as  in  honeys  and  fruit  products,  the 
optical  method  for  sucrose  gives  too  high  a  result. 


ANALYSIS  OF  FOODSTUFFS  401 

(1)  For  substances  in  which  the  invert  solution  contains  more 
than  12  grams  of  invert  sugar  per  100  cc. : 

The  following  formula  is  to  be  used  when  substances  like  raw 

100  (P-7) 
sugars  are  polarized :    S  =  —          — — , 

142.66-- 

in  which  $  =  per  cent  of  sucrose; 

P  =  direct  reading  of  normal  solution  ; 

7  =  invert  reading  of  normal  solution; 
and  T  =  temperature  at  which  readings  are  made. 

(2)  For  substances  in  which  the  concentration  of  the  invert 
solution  is  less  than  12  grams  per  100  cc. : . 

The  following  formula,  which  takes  into  account  the  concen- 
tration of  the  sugar  in  solution,  should  be  used  in  all  other  cases: 

100  (P-7) 


T  f  T  V 

142.66--- 0.0065   142.66---  (P-7) 

in  which  S  =  per  cent  of  sucrose, 

P  =  direct  reading  of  normal  solution, 

7  =  invert  reading  of  normal  solution, 
and  T = temperature. 

(D)  DETERMINATION  OF  SUCROSE  AND  RAFFINOSE  (of  value 
chiefly  in  analysis  of  beet  products). — If  the  direct  reading  is 
more  than  1°  higher  than  the  per  cent  of  sucrose  as  calculated  by 
the  formula  given  above,  raffinose  is  probably  present.  Calculate 
sucrose  and  raffinose  by  the  following  formula  of  Herzf eld  : 

0.5124  P-7  P-S 

-0839-  *  = 

in  which  P  =  direct  reading  of  normal  solution; 

7  =  in  vert  reading  of  normal  solution; 

/S  =  per  cent  of  sucrose; 
and          R  =  per  cent  of  anhydrous  raffinose. 


402  TECHNICAL  METHODS  OF  ANALYSIS 

The  above  formula  assumes  that  polarizations  are  made  at  exactly 
20°  C.  If  the  temperature  (T)  is  other  than  20°  C.,  the  following 
formula  should  be  used : 

P  (0.4724 +0.002  T)-/ 
o  = 


Having  calculated  S,  then  R  = 


0.899-0.003  T 
P-S 


1.852' 


(2)  Chemical  Methods. — (A)  DETERMINATION  OF  SUCROSE 
FROM  REDUCING  SUGARS  BEFORE  AND  AFTER  INVERSION  (TENTA- 
TIVE).— Determine  the  reducing  sugars  (clarification  having  been 
effected  with  neutral  lead  acetate,  never  with  basic  lead  acetate),  as 
directed  below  under  Munson  and  Walker  Method  and  calculate  to 
invert  sugar  from  the  M.  and  W.  tables.  Then  invert  the  solution 
as  directed  above  (under  Polarization  before  and  after  Inversion 
with  HC1),  exactly  neutralize  the  acid  and  again  determine  the 
reducing  sugars;  but  calculate  them  to  invert  sugar  from  the  same 
table  as  just  referred  to,  using  the  invert  sugar  column  alone. 
Deduct  the  per  cent  of  invert  sugar  determined  before  inversion 
from  that  obtained  after  inversion,  and  multiply  the  difference  by 
0.95;  the  result  is  the  per  cent  of  sucrose.  The  solution  should 
be  diluted  in  both  determinations  so  that  not  more  than  245  mg. 
of  invert  sugar  are  present  in  the  amount  taken  for  reduction. 
It  is  also  important  that  all  Pb  be  removed  from  the  solution  with 
K2C2O4  before  reduction. 

(II)  TOTAL  REDUCING  SUGARS 

General. — The  determination  of  reducing  sugars  by  copper 
reduction  depends  upon  the  reduction  of  an  alkaline  copper 
solution  by  the  action  of  the  reducing  sugars,  precipitating  red 
Cu2O.  Since  the  extent  of  the  reduction  varies  under  different 
conditions,  it  is  necessary  that  the  directions  be  strictly  adhered  to. 

Of  the  common  sugars,  sucrose  is  the  only  one  which  has  no 
direct  reducing  action  on  alkaline  copper  tartrate;  but  on  under- 
going inversion,  it  is  converted  into  reducing  sugars  which  can  be 
readily  determined. 


ANALYSIS  OF  FOODSTUFFS  403 

There  are  various  methods,  all  based  on  the  reduction  of  Cu 
salts,  but  varying  in  detail.  For  all  ordinary  use  the  Munson  and 
Walker  method  is  the  most  convenient,  since  the  Cu2O  can  be 
calculated  directly  to  dextrose,  invert  sugar,  maltose  or  lactose, 
as  the  case  may  be.  It  is  not  well  adapted,  however,  to  the  deter- 
mination of  lactose  (milk  sugar)  in  the  presence  of  sucrose,  for 
instance  in  sweetened  condensed  milk  or  in  sweetened  milk  choco- 
late, on  account  of  partial  inversion  of  the  sucrose  by  the  boiling. 
In  such  case  it  is  necessary  to  use  the  Defren-O'Sullivan  method. 

(1)  Munson  and  Walker  Method  (Tentative). — (A)  REAGENTS. 
(a)  Fehling's  copper  sulfate  solution.* — Dissolve  34.639  grams 
of  carefully  selected  crystals  of  pure  CuSO4-5H2O  in  distilled 
water.  Dilute  to  exactly  500  cc.  and  filter  through  prepared 
asbestos. 

(b)  Fehling's  alkaline  tartrate  solution.* — Dissolve  173  grams 
of  Rochelle  salts  (KNaC^Oo  •  4H2O)  and  50  grams  of  NaOH  in 
water,  dilute  to  exactly  500  cc.,  let  stand  two  days,  and  filter 
through  prepared  asbestos. 

(c)  Asbestos. — Prepare  the  asbestos  (which  should  be  of  the 
amphibole  variety)  by  first  digesting  with  HC1  (1:3)  for  two  or 
three  days.     Wash  free  from  acid  and  digest  for  a  similar  period 
with  10%  NaOH  solution.     Then  treat  for  a  few  hours  with  hot 
alkaline  tartrate  solution  of  the  strength  employed  in  the  sugar 
determinations.     (Old  alkaline  tartrate  solutions  that  have  stood 
for  some  time  may  be  used.)     Then  wash  free  from  alkali.     Finally 
digest  with  dil.  HNOs  for  several  hours,  and,  after  washing  free 
from  acid,  shake  with  water  for  use.     In  preparing  the  Gooch 
crucible,  load  it  with  a  film  of  asbestos  0.25  inch  thick.     Wash 
this  thoroughly  with  water  to  remove  fine  particles  of  asbestos. 
Finally  wash  with  alcohol  and  then  with  ether.     Dry  for  thirty 
minutes  at  100°  C.,  cool  in  a  desiccator  and  weigh.     It  is  best  to 
dissolve  the  Cu20  with  HNOs  each  time  after  weighing  and  use 
the  same  felts  repeatedly,  as  they  improve  with  use. 

(B)  PROCEDURE. — Transfer  25  cc.  each  of  the  copper  and  the 
alkaline  tartrate  solutions  to  a  400  cc.  beaker  of  alkali-resisting 
glass,  and  add  50  cc.  of  the  reducing  sugar  solution,  which  must  be 
neutral  or  slightly  alkaline;  or,  if  a  smaller  volume  of  sugar  solu- 
tion be  used,  add  water  to  make  the  final  volume  100  cc.  Heat 
*  Soxhlet  modification. 


404  TECHNICAL  METHODS  OF  ANALYSIS 

the  beaker  on  an  asbestos  gauze  over  a  Bunsen  burner;  so  regulate 
the  flame  that  boiling  begins  in  four  minutes,  and  continue  boiling 
for  exactly  two  minutes.* 

Keep  the  beaker  covered  with  a  watch  glass  throughout  the 
heating.  Without  diluting,  filter  the  Cu2O  at  once  on  the  asbestos 
felt  in  a  porcelain  Gooch  crucible,  using  suction.  Wash  the  Cu20 
thoroughly  with  water  at  about  60°  C.,  then  with  10  cc.  of  alcohol, 
and  finally  with  10  cc.  of  ether.  Dry  for  thirty  minutes  in  the 
water  oven  at  100°  C.,  cool  in  desiccator  and  weigh  as  Cu2O. 

Calculate  from  the  weight  of  the  Cu2O  (see  note  (3)  below) 
the  amount  of  reducing  sugars  according  to  Munson  and  Walker's 
tables.  These  tables  may  be  found  in  Leach:  "  Food  Inspection 
and  Analysis,"  4th  Ed.,  page  623;  also  in  J.  Assoc.  Official  Agr. 
Chemists,  2,  Methods  of  Analysis  (1916),  pages  88-96. 

NOTES. — (1)  The  number  of  milligrams  of  Cu  reduced  by  a  given  amount 
of  reducing  sugar  differs  when  sucrose  is  present  and  when  it  is  absent.  In 
the  tables,  the  absence  of  sucrose  is  assumed,  except  in  the  columns  under 
invert  sugar,  where  the  total  amount  of  sugar  in  50  cc.  of  solution  is  given. 

(2)  Blank  determination:    Always  conduct  a  blank  determination,  using 
50  cc.  of  reagent  and  50  cc.  of  water;  and  if  the  weight  of  the  Cu2O  obtained 
exceeds  0.0005  gram,  correct  the  result  of  the  reducing  sugar  determination 
accordingly.     The  alkaline  tartrate  solution  deteriorates  on  standing  and  the 
amount  of  Cu2O  obtained  in  the  blank  increases. 

(3)  The  method  of  direct  weighing  of  the  Cu2O  should  be  used  only  for 
determinations  in  pure  sugar  solutions;  in  all  other  cases  the  Cu  of  the  Cu2O 
should  be  determined  by  one  of  the  following  methods,  since  the  Cu2O  is  very 
apt  to  be  contaminated  with  foreign  matter. 

(C)  DETERMINATION  OF  COPPER  REDUCED.— 

(a)  Electrolysis  from  #2$04  solution  (tentative). — Filter  the 
Cu2O  in  a  Gooch  crucible  and  wash  the  beaker  and  precipitate 
thoroughly  with  hot  water  without  transferring  the  precipitate  to 
the  filter.  Wash  the  asbestos  film  and  adhering  Cu20  into  the 
beaker  by  means  of  hot  dil.  HNOs.  After  all  the  Cu  is  in  solu- 
tion, refilter  through  a  thin  mat  of  asbestos  in  a  Gooch  crucible 
and  wash  thoroughly  with  hot  water.  Add  10  cc.  of  H2SO4  (1:4) 
and  evaporate  the  filtrate  on  the  steam  bath  until  the  Cu  salt  has 

*  It  is  important  that  these  directions  be  strictly  observed.  In  order  to 
regulate  the  burner  for  this  purpose,  it  is  advisable  to  make  preliminary  tests, 
using  50  cc.  of  the  reagent  and  50  cc.  of  water,  before  proceeding  with  the 
actual  determination. 


ANALYSIS  OF  FOODSTUFFS  405 

largely  crystallized.  Heat  carefully  on  a  hot  plate  or  over  asbestos 
until  the  evolution  of  white  fumes  shows  that  the  excess  of  HNOs 
is  removed.  Add  8-10  drops  of  cone.  HNOs  and  rinse  into  a 
100-125  cc.  platinum  dish.  Deposit  the  Cu  upon  the  dish  by 
electrolysis.  Wash  thoroughly  with  water,  then  break  the  cur- 
rent, wash  with  alcohol  and  ether  successively,  dry  at  about  50°  C., 
and  weigh.  If  preferred,  the  electrolysis  may  be  conducted  in  a 
beaker,  the  Cu  being  deposited  upon  a  weighed  platinum  electrode. 

(b)  Electrolysis  from  H2S04  and  HNOs  solution   (tentative). — 
Filter  and  wash  as  directed  above.     Transfer  the  asbestos  mat 
from  the  crucible  to  the  beaker  by  means  of  a  glass  rod  and  rinse 
the  crucible  with  about  30  cc.  of  a  boiling  mixture  of  dil.  sulfuric 
and  nitric  acids,  containing  65  cc.   of  cone.  H2SO4  and  50  cc. 
of  cone.  HNOs  per  liter.     Heat  and  agitate  until  solution  is  com- 
plete; filter  and  electrolyze  as  above. 

(c)  Electrolysis  from  HNOs    solution    (tentative). — Filter    and 
wash  as  directed  above.     Transfer  the  asbestos  mat  and  adhering 
Cu2O  to  the  beaker.     Dissolve  the  oxide  still  remaining  in  the 
crucible  by  means  of  2  cc.  of  cone.  HNOs,  adding  it  with  a  pipette 
and  collecting  the  solution  in  the  beaker  containing  the  asbestos. 
Rinse  the  crucible  with  a  jet  of  water,  letting  the  rinsings  flow 
into  the  beaker.     Heat  the  contents  of  the  beaker  until  all  Cu  is 
in  solution;    filter,  wash,  dilute  the  filtrate  to  100  cc.  or  more, 
and  electrolyze.     When  a  nitrate  solution  is  electrolyzed,   the 
first  washings  of  the  deposit  should  be  made  with  water  acidulated 
with  H2SO4  in  order  to  remove  all  HNOs  before  the  current  is 
interrupted. 

(2)  Defren-O'Sullivan  Method.*— (A)  REAGENTS.— The  solu- 
tions used  in  this  procedure  are  the  same  as  those  for  the  Munson 
and  Walker  method  above  described.  The  asbestos  used  should 
be  of  the  long  fiber  variety  and  should  be  specially  prepared  as 
follows:  Boil  first  with  HNO3  (about  1:6).  Wash  out  the  acid 
with  hot  water  and  then  boil  with  a  25%  solution  of  NaOH, 
and  finally  wash  out  the  alkali  with  hot  water.  Keep  the  asbestos 
in  a  wide-mouth  flask  or  bottle  and  transfer  it  to  the  Gooch 
crucible  by  shaking  up  in  the  water  and  pouring  it  quickly  into 
the  crucible  while  under  suction. 

*  This  method  is  described  in  Leach:  "  Food  Inspection  and  Analysis," 
4th  Ed.,  page  618. 


406  TECHNICAL  METHODS  OF  ANALYSIS 

(B)  PROCEDURE. — Mix  15  cc.  of  Fehling's  Cu  solution  with 
15  cc.  of  the  tartrate  solution  in  a  250  cc.  Erlenmeyer  flask,  and  add 
50  cc.  of  distilled  water.  Place  the  flask  and  contents  in  a  boiling 
water  bath  and  let  remain  five  minutes.  Then  run  rapidly  from  a 
burette  into  the  hot  liquor  in  the  flask  25  cc.  of  the  sugar  solution 
to  be  tested  (which  should  contain  not  over  0.5%  of  reducing 
sugars).  Let  the  flask  remain  in  the  boiling  water  bath  exactly 
fifteen  minutes  after  the  addition  of  the  sugar  solution;  remove, 
and  with  the  aid  of  suction  filter  the  contents  rapidly  in  a  Gooch 
crucible  containing  a  layer  of  prepared  asbestos  fiber  about  1  cm. 
thick,  the  Gooch  crucible  with  the  asbestos  having  been  previously 
ignited,  cooled  and  weighed.  Wash  the  Cu2O  precipitate  thor- 
oughly with  boiling  distilled  water  till  the  filtrate  is  no  longer 
alkaline. 

Dry  the  Gooch  crucible  with  contents  in  the  oven,  and  finally 
heat  to  dull  redness  for  fifteen  minutes,  during  which  the  red 
Cu2O  is  converted  into  black  CuO.  If  a  platinum  Gooch  crucible 
is  used  (which  is  preferable)  it  may  be  heated  directly  over  the 
low  flame  of  a  burner.  If  the  Gooch  crucible  is  of  porcelain,  con- 
siderable care  must  be  taken  to  avoid  cracking,  the  heat  being 
increased  cautiously  and  the  operation  preferably  conducted  in  a 
radiator  or  muffle.  After  oxidation  as  above,  transfer  the  crucible 
to  a  desiccator,  cool,  and  weigh  quickly.  From  the  milligrams  of 
CuO,  calculate  the  milligrams  of  dextrose,  etc.,  as  the  case  may 
be,  and  calculate  to  per  cent  of  the  original  sample.  (See  table 
in  Leach,  page  619.) 

(Ill)  INDIVIDUAL  REDUCING  SUGARS 

(A)  Invert  Sugar. — The  methods  for  total  reducing  sugars  pre- 
viously given,  also  apply  to  the  determination  of  invert  sugar.* 
The  following  method  is  the  tentative  approximate  volumetric 
method  for  rapid  work  of  the  Association  of  Official  Agricultural 
Chemists. 

(1)  REAGENT:  Soxhlet's  modification  of  Fehling's  solution. — 
Prepare  by  mixing,  immediately  before  use,  equal  volumes  of 
reagents  (a)  and  (6)  described  previously  under  the  Munson  and 
Walker  Method. 

*  See  also  under  (D)  below  (page  408) . 


ANALYSIS  OF  FOODSTUFFS  407 

(2)  STANDARDIZATION  OF  COPPER  SOLUTION. — Since  the  factor 
for  calculation  varies  with  the  minute  details  of  manipulation, 
every  operator  must  determine  a  factor  for  himself,  using  a  known 
solution  of  the  pure  sugar  that  he  desires  to  determine,  and  keeping 
the  conditions  the  same  as  those  used  for  the  determination. 

Standardize  the  solution  for  invert  sugar  in  the  following  man- 
ner: Dissolve  4.75  grams  of  pure  sucrose  in  75  cc.  of  water,  add 
5  cc.  of  cone.  HC1  and  invert  with  HC1  as  described  above  under 
Polarization  (Sucrose  in  the  Absence  of  Raffinose).  Neutralize 
the  acid  with  NaOH  solution  and  dilute  to  1  liter.  Ten  cc.  of  this 
solution  contain  0.050  gram  of  invert  sugar,  which  should  reduce 
10  cc.  of  the  reagent.  The  strength  of  the  copper  solution  should 
never  be  taken  as  constant,  but  should  be  checked  against  the 
sugar. 

(3)  DETERMINATION. — Place  10  cc.  of  the  reagent  in  a  large 
test-tube  and  add  10  cc.  of  water.     Heat  to  boiling,  and  add  grad- 
ually small  portions  of  the  solution  of  the  material  to  be  tested 
until  the  copper  has  been  completely  reduced,  boiling  after  each 
addition   to    complete    the    reaction.     Two    minutes'    boiling   is 
required  for  complete  reduction  when  the  full  amount  of  sugar 
solution  has  been  added  in  one  portion.     When  the  end  is  nearly 
reached  and  the  amount  of  sugar  solution  to  be  added  can  no  longer 
be  judged  by  the  color  of  the  solution,  remove  a  small  portion  of 
the  liquid  and  filter  rapidly  into  a  small  porcelain  crucible  or  on  a 
test  plate;    acidify  with  dilute  acetic  acid,  and  test  for  Cu  with 
dilute    potassium    ferrocyanide    solution.     The    sugar    solution 
should  be  of  such  strength  as  will  give  a  burette  reading  of  15-20 
cc.  and  the  number  of  successive  additions  should  be  as  small  as 
possible. 

(B)  Dextrose:  Allihn's  Gravimetric  Method  (Tentative).— 

(1)  REAGENT:  Allihn's  modification  of  Fehling's  solution. 
Prepare  by  mixing, 'immediately  before  use,  equal  volumes  of 

(a)  and  (6). 

(a)  Copper  sulfate  solution:  Dissolve  34.639  grams  of 
CuS04-5H2O  in  water  and  dilute  to  500  cc. 

(6)  Alkaline  tartrate  solution:  Dissolve  173  grams  qf  Rochelle 
salts  and  125  grams  of  KOH  in  water  and  dilute  to  500  cc. 

(2)  DETERMINATION. — Place  30  cc.  of  the  CuSCU  solution,  30  cc. 
of  the  alkaline  tartrate  solution  and  60  cc.  of  water  in  a  beaker  and 


408  TECHNICAL  METHODS  OF  ANALYSIS 

heat  to  boiling.  Add  25  cc.*  of  the  solution  of  the  material  to  be 
examined,  prepared  so  as  not  to  contain  more  than  0.25  gram  of 
dextrose,  and  boil  for  exactly  two  minutes,  keeping  the  beaker 
covered.  Filter  immediately  through  asbestos,  and  obtain  the 
weight  of  Cu  by  one  of  the  procedures  given  under  the  Munson  and 
Walker  method  above.  From  the  Allihn  tables  determine  the  cor- 
responding weight  of  dextrose.  The  Allihn  tables  are  given  in 
J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis  (1916), 
pages  107-108;  also  in  Leach:  "  Food  Inspection  and  Analysis," 
4th  Ed.,  page  633. 

NOTE. — This  method  may  also  be  used  for  various  other  reducing  sugars 
as  described  below. 

(C)  Maltose,  Lactose,  Dextrose. — Use  the  Munson  and  Walker 
general  method  as  described  above  and  calculate  from  the  table 
the  weight  of  maltose,  lactose  or  dextrose  equivalent  to  the  weight 
of  the  Cu  reduced. 

(D)  Levulose,  Invert  Sugar,  Arabinose,  Xylose,  Galactose. — 
For  the  determination  of  these  reducing  sugars  use   the  Allihn 
method  as  described  above  and  multiply  the  weight  of  dextrose 
found  in  the  Allihn  tables  by  the  following  factors: 

Levulose 1.093 

Invert  sugar 1 . 046 

Arabinose 0.969 

Xylose 1.017 

Galactose 1.114 

REFERENCES. — U.  S.  Dept.  of  Agriculture,  Bureau  of  Chemistry,  Bulletin 
107,  page  241;  Leach:  "Food  Inspection  and  Analysis";  J.  Assoc.  Official 
Agr.  Chemists,  Methods  of  Analysis  (1916),  pages  81-109. 

• 
SACCHARINE  PRODUCTS 

General. — This  method  applies  to  the  usual  determinations 
common  to  all  Saccharine  Products,  i.e.,  those  containing  one  or 

*  If  necessary,  the  volume  of  the  sugar  solution  added  may  be  greater  or 
less  than  25  cc.,  provided  the  volume  of  water  added  is  correspondingly 
varied  from  60  cc.,  so  that  the  total  volume  of  sugar  solution  and  water 
added  is  always  85  cc. 


ANALYSIS  OF  FOODSTUFFS  409 

more  sugars.  For  complete  analysis  of  special  products  see  the 
method  for  that  particular  material,  e.g.,  Sugar,  Honey,  Maple 
Products,  Sucrose  in  Beets,  etc. 

The  methods  here  given  are,  unless  otherwise  specified,  the 
official  methods  of  the  Association  of  Official  Agricultural  Chemists. 

Preparation  of  Sample  (Tentative). — (a)  Liquids  (molasses, 
syrups,  etc.) — Mix  materials  of  this  class  thoroughly.  If  crystals 
of  sugar  are  present,  dissolve  them  either  by  heating  gently  or  by 
weighing  the  whole  mass,  then  adding  water,  heating  until  com- 
pletely dissolved  and,  after  cooling,  re-weighing.  Calculate  all 
results  to  the  weight  of  the  original  substance. 

(b)  Semi-solids  (jellies,  jams,  etc.). — Weigh   50   grams  of  the 
sample  into  a  250  cc.  graduated  flask.     Treat  with  water,  fill 
to  the  mark  and  mix  thoroughly.     If  insoluble  material  remains, 
mix  uniformly  by  shaking  before  taking  aliquots  for  the  various 
determinations. 

(c)  Solids  (sugar,  confectionery,  etc.). — Grind    and   mix   thor- 
oughly materials  of  this  class  to  secure  uniform  samples. 

Moisture. — (A)  SUGAKS. — Dry  2-5  grams  in  a  flat  dish  (nickel, 
platinum,  or  aluminum)  at  not  over  110°  C.  for  ten  hours;  cool 
in  a  desiccator  and  weigh;  then  dry  again  for  an  hour,  or  until 
there  is  only  a  slight  change  in  weight. 

(B)  MASSECUITES,  MOLASSES  AND  OTHER  LIQUID  AND  SEMI- 
LIQUID  PRODUCTS — 

(1)  Drying  upon  pumice  stone  (tentative). 

Prepare  pumice  stone  of  2  grades  of  fineness,  one  of  which  will 
pass  through  a  1  mm.  sieve,  the  other  through  a  6  mm.  sieve. 
Make  the  determination  in  flat  metallic  dishes  or  in  shallow,  flat- 
bottomed,  weighing  bottles.  Place  a  layer  of  the  fine  pumice 
stone,  3  mm.  in  thickness,  on  the  bottom  of  the  dish,  then  a  layer 
of  the  coarse  pumice  stone  6-10  mm.  in  thickness,  dry  and  weigh. 
Dilute  the  sample  with  a  weighed  portion  of  water  so  that  the 
diluted  material  shall  contain  20-30%  of  solid  matter.  Weigh 
into  the  dish,  prepared  as  described  above,  an  amount  of  the 
diluted  sample  to  yield  approximately  1  gram  of  dry  matter.  If 
this  weighing  cannot  be  made  rapidly,  use  a  weighing  bottle  pro- 
vided with  a  cork  through  which  a  pipette  passes.  Dry  in  vacuo 
a.t  70°  C.  to  constant  weight,  making  trial  weighings  at  intervals 
of  two  hours.  For  substances  containing  little  or  no  levulose  or 


410  TECHNICAL  METHODS  OF  ANALYSIS 

other  readily  decomposable  substance,  the  drying  may  be  made  in  a 
water  oven  at  the  temperature  of  boiling  water. 

(2)  Drying  upon  quartz  sand  (tentative). 

Digest  pure  quartz  sand  with  cone.  HC1,  wash,  dry  and 
ignite.  .  Preserve  in  a  stoppered  bottle.  Place  6-7  grams  of 
the  prepared  sand  and  a  short  stirring  rod  in  a  flat-bottomed 
dish.  Dry  thoroughly,  cool  in  a  desiccator,  and  weigh.  Then  add 
3^  grams  of  the  molasses,  mix  with  the  sand  (if  necessary  to 
thoroughly  incorporate  the  two,  add  a  little  water),  dry  in  a 
water  oven  at  the  temperature  of  boiling  water  for  eight  to  ten 
hours,  stirring  at  intervals  of  an  hour;  cool  in  a  desiccator,  and 
weigh.  Stir,  heat  again  for  an  hour,  cool,  and  weigh.  Repeat 
the  heating  and  weighing  until  the  loss  of  weight  in  an  hour  is  not 
greater  than  0.003  gram. 

Specific  Gravity,  Water,  and  Total  Solids. — (A)  BY  MEANS  OF 
A  SPINDLE. — The  density  of  juices,  syrups,  etc.,  is  most  conveniently 
determined  by  means  of  the  Brix  hydrometer.  For  rough  work, 
or  where  less  accuracy  is  desired,  the  Baum^  hydrometer  may  be 
used.  The  Brix  spindle  should  be  graduated  to  tenths.  The 
range  of  degrees  recorded  by  each  individual  spindle  should  be  as 
limited  as  possible.  The  solution  should  be  as  nearly  as  prac- 
ticable of  the  same  temperature  as  the  air  at  the  time  of  reading, 
and,  if  the  variation  from  the  temperature  of  the  graduation  of 
the  spindle  amounts  to  more  than  1°,  a  correction  must  be  applied 
according  to  Table  II.  Before  taking  the  density  of  a  juice,  let  it 
stand  in  the  cylinder  until  all  air  bubbles  have  escaped,  and  until 
all  fatty  or  waxy  matter  has  come  to  the  surface  and  been  skimmed 
off.  The  cylinder  should  be  large  enough  in  diameter  to  allow 
the  hydrometer  to  come  to  rest  without  touching  the  sides.  A 

20° 
table  of  sp.  gr.  at  —-  and  per  cent  by  weight  of  sucrose  is  given 

on  page  125  of  the  Journal  of  the  Assoc.  Official  Agri.  Chemists, 
Vol.  2,  Methods  of  Analysis  (1916);  and  a  table  for  the  compar- 

17  5° 

ison   of  sp.  gr.  at         0  with  degrees   Brix  (per   cent   by  weight 
17.5 

of  sucrose)  and  degrees  Baume  is  given  below  in  Table  I. 

If  the  sample  is  too  dense  to  determine  the  gravity  directly, 
dilute  a  weighed  portion  with  a  weighed  quantity  of  water,  or  dis- 
solve a  weighed  portion  and  dilute  to  a  known  volume  with  water. 


ANALYSIS  OF  FOODSTUFFS 


411 


TABLE  I 

17  5° 

Comparison  of  specific  gravities  at      '  0  C.,  degrees  Brix  and  Baum6. 

l  /  .o 

•Degrees  Baume  =  146  78-^— . 
sp.  gr. 


Degree 

Degree 

Degree 

Brix  or 

Brix  or 

Brix  or 

Per 
Cent 
byWt. 

Specific 
Gravity 

Degree 
Baume 

Per 

Cent 
byWt. 

Specific 
Gravity 

Degree 
Baume 

Per 
Cent 
byWt 

Specific 
Gravity 

Degree 
Baum6 

of  Su- 

of Su- 

of Su- 

crose 

crose 

crose 

1.0 

1.00388 

0.6 

33.0 

1  .  14423 

18.5 

65.0 

1.31989 

35.  b 

2.0 

1.00779 

1.1 

34.0 

1.14915 

19.05 

66.0 

1.32601 

36.1 

3.0 

1.01173 

1.7 

35.0 

1.15411 

19.6 

67.0 

1.33217 

36.6 

4.0 

1.01570 

2.3 

36.0 

1.15911 

20.1 

68.0 

1.33836 

37.1 

5.0 

1.01970 

2.8 

37.0 

1.16413 

20.7 

69.0 

1.34460 

37.6 

6.0 

1.02373 

3.4 

38.0 

1.16920 

21.2 

70.0 

1.35088 

38.1 

7.0 

1.02779 

4.0 

39.0 

1.17430 

21.8 

71.0 

1.35720 

38.6 

8.0 

1.03187 

4.5 

40.0 

1.17943 

22.3 

72.0 

1.36355 

39.1 

9.0 

1.03599 

5.1 

41.0 

1.18460 

22.9 

73.0 

1.36995 

39.6 

10.0 

1.04014 

5.7 

42.0 

1.18981 

23.4 

74.0 

1.37639 

40.1 

11.0 

1.04431 

6.2 

43.0 

1.19505 

23.95 

75.0 

1.38287 

40.6 

12.0 

1.04852 

6.8 

44.0 

1.20033 

24.5 

76.0 

1.38939 

41.1 

13.0 

1.05276 

7.4 

45.0 

1.20565 

25.0 

77.0 

1.39595 

41.6 

14.0 

1.05703 

7.9 

46.0 

1.21100 

25.6 

78.0 

1.40254 

42.1 

15.0 

1.06133 

8.5 

47.0 

1.21639 

26.1 

79.0 

1.40918 

42.6 

16.0 

1.06566 

9.0 

48.0 

1.22182 

26.6 

80.0 

1.41586 

43.1 

17.0 

1.07002 

9.6 

49.0 

1.22728 

27.2 

81.0 

1.42258 

43.6 

18.0 

1.07441 

10.1 

50.0 

1.23278 

27.7 

82.0 

1.42934 

44.1 

19.0 

1.07884 

10.7 

51.0 

1.23832 

28.2 

83.0 

1.43614 

44.6 

20.0 

1.08329 

11.3 

52.0 

1.24390 

28.8 

84.0 

1.44298 

45.1 

21.0 

1.08778 

11.8 

53.0 

1.24951 

29.3 

85.0 

1.44986 

45.5 

22.0 

1.09231 

12.4 

54.0 

1.25517 

29.8 

86.0 

1.45678 

46.0 

23.0 

1.09686 

13.0 

55.0 

1.26086 

30.4 

87.0 

1.46374 

46.5 

24.0 

1.10145 

13.5 

56.0 

1.26658 

30.9 

88.0 

1.47074 

47.0 

25.0 

1.10607 

14.1 

57.0 

1.27235 

31.4 

89.0 

1.47778 

47.45 

26.0 

1.11072 

14.6 

58.0 

1.27816 

31.9 

90.0 

1.48486 

47.9 

27.0 

1.11541 

15.2 

59.0 

1.28400 

32.5 

91.0 

1.49199 

48.5 

28.0 

1.12013 

15.7 

60.0 

.28989 

33.0 

92.0 

1.49915 

48.9 

29.0 

1  .  12488 

16.3 

61,0 

.29581 

33.5 

93.0 

1.50635 

49.4 

30.0 

1  .  12967 

16.8 

62.0 

.30177 

34.0 

94.0 

1.51359 

49.8 

31.0 

1.13449 

17.4 

63.0 

.30777 

34.5 

95.0 

1.52087 

50.3 

32.0 

1.13934 

17.95 

64.0 

.31381 

35.1 

412  TECHNICAL  METHODS  OF  ANALYSIS 

In  the  first  instance  the  per  cent  of  total  solids  is  calculated 
by  the  following  formula : 

WS 

Per  cent  of  solids  in  undiluted  material  = , 

w 

in  which  S  =  per  cent  of  solids  in  diluted  material ; 

W  =  weight  of  diluted  material ; 
and          w  =  weight  of  sample  taken  for  dilution. 

When  the  dilution  is  made  to  a  definite  volume,  the  following 
formula  is  to  be  used : 

Per  cent  of  solids  in  the  undiluted  material  =  —  — , 

W 

in  which  V  =  volume  of  diluted  solution  at  a  given  temperature  ; 
D  =  sp.  gr.  of  diluted  solution  at  same  temperature ; 
S  =  per  cent  of  solids  in  diluted  solution  at  same  tempera- 
ture; 

and          W  =  weight  of  sample  taken  for  dilution  at  same  tempera- 
ture. 

If  the  spindls  reading  be  made  at  any  other  temperature  than 
17.5°  C.,  the  result  should  be  corrected  according  to  Table  II. 

(B)  BY  MEANS  OF  A  PYCNOMETER. 

20° 

(1)  Specific  gravity  at   —C. 

4 

20° 
Determine  the  sp.  gr.  of  the  solution  at  — —  C.  by  means  of  a 

pycnometer  and  ascertain  the  corresponding  per  cent  by  weight 
of  sucrose  from  official  tables.  When  the  density  of  the  substance 
is  too  high  for  a  direct  determination,  dilute  and  calculate  the 
sucrose  content  of  the  original  material  as  directed  above. 

17  53 

(2)  Specific  gravity  at  — ~  C. 

17 .o 

17  5° 

Determine  the  sp.  gr.  at  -— '—  C.   with  a  pycnometer  and 

17.5 

ascertain  the  corresponding  per  cent  by  weight  of  sucrose  from 
Table  I. 

NOTE. — Pycnometer  determinations  must  not  be  made  at  any  other 
temperature  than  those  given. 


ANALYSIS  OF  FOODSTUFFS 


413 


TABLE  II 

Corrections  of  Brix  spindle  readings  for  temperatures 
other  than  standard  (17.5°  C.) 


Tempera- 
ture °  C. 

0 

5 

10 

15 

20 

25 

30 

35 

40 

50 

60 

70 

75 

0 

0.17 

0.30 

0.41 

0.52 

0.62 

0.72 

0  82 

0.92 

0.98 

1.11 

1.22 

1.25 

1.29 

5 

0.23 

0.30 

0.37 

0.44 

0.52 

0.59 

0.65 

0.72 

0.75 

0.80 

0.88 

0.91 

0.94 

10 

0.20 

0.26 

0.29 

0.33 

0.36 

0.39 

0.42 

0.45 

0.48 

0.50 

0.54 

0.58 

0.61 

11 

0.18 

0  23 

0.26 

0.28 

0.31 

0.34 

0.36 

0.39 

0.41 

0.43 

0.47 

0.50 

0.53 

12 

0.16 

0.20 

0.22 

0.24 

0.26 

0.29 

0.31 

0.33 

0.34 

0.36 

0.40 

0.42 

0.46 

13 

0.14 

0.18 

0.19 

0.21 

0.22 

0.24 

0.26 

0.27 

0.28 

0.29 

0.33 

0.35 

0.39 

14 

0.12 

0.15 

0.16 

0.17 

0.18 

0.19 

0.21 

0.22 

0.22 

0.23 

0.26 

0.28 

0.32 

15 

0.09 

0.11 

0.12 

0.14 

0.14 

0.15 

0.16 

0.17 

0.16 

0.17 

0.19 

0.21 

0.25 

16 

0.06 

0.07 

0.08 

0.09 

0.10 

0.10 

0.11 

0.12 

0.12 

0.12 

0.14 

0.16 

0.18 

17 

0.02 

0:02 

0.03 

0.03 

0.03 

0.04 

0.04 

0.04 

0.04 

0.05 

0.05 

0.05 

0.06 

18 

0.02 

0.03 

0.03 

0.03 

0.03 

0.03 

0.03 

0.03 

0.03 

0.03 

0  03 

0.03 

0.02 

19 

0.06 

0.08 

0.08 

0.09 

0.09 

0.10 

0.10 

0.10 

0.10 

0.10 

0.10 

0.08 

0.06 

20 

0.11 

0.14 

0.15 

0.17 

0.17 

0.18 

0.18 

0.18 

0.19 

0.19 

0.18 

0.15 

0.11 

21 

0.16 

0.20 

0.22 

0.24 

0.24 

0.25 

0.25 

0.25 

0.26 

0.26 

0.25 

0.22 

0.18 

22 

0.21 

0.26 

0.29 

0.31 

0.31 

0.32 

0.32 

0.32 

0.33 

0.34 

0.32 

0.29 

0.25 

23 

0.27 

0.32 

0.35 

0.37 

0.38 

0.39 

0.39 

0.39 

0.40 

0.42 

0.39 

0.36 

0.33 

24 

0.32 

0.38 

0.41 

0.43 

0.44 

0.46 

0  46 

0.47 

0.47 

0.50 

0.46 

0.43 

0.40 

25 

0.37 

0.44 

0.47 

0.49 

0.51 

0.53 

0.54 

0.55 

0.55 

0.58 

0  54 

0.51 

0.48 

26 

0.43 

0.50 

0.54 

0.56 

0.58 

0.60 

0.61 

0.62 

0.62 

0.66 

0.62 

0.58 

0  55 

27 

0.49 

0.57 

0.61 

0.63 

0.65 

0.68 

0.68 

0.69 

0.70 

0.74 

0.70 

0  65 

0.62 

28 

0.56 

0.64 

0.68 

0.70 

0.72 

0.76 

0.76 

0.78 

0.78 

0.82 

0.78 

0.72 

0.70 

29 

0.63 

0.71 

0.75 

0.78 

0.79 

0.84 

0.84 

0.86 

0.86 

0.90 

0.86 

0.80 

0.78 

30 

0.70 

0.78 

0.82 

0.87 

0.87 

0.92 

0.92 

0.94 

0.94 

0.98 

0.94 

0.88 

0.86 

35 

1.10 

1.17 

1.22 

1.24 

1.30 

1.32 

1.33 

1.35 

1.36 

1.39 

1.34 

1.27 

1.25 

40 

1.50 

1.61 

1.67 

1.71 

1.73 

1.79 

1.79 

1.80 

1.82 

1.83 

1.78 

1.69 

1.65 

50 

2.65 

2.71 

2.74 

2.78 

2.80 

2.80 

2.80 

2.80 

2.79 

2.70 

2.56 

2.51 

60 

3.87 

3.88 

3.88 

3.88 

3.88 

3.88 

3.88 

3.90 

3.82 

3.70 

3.43 

3.41 

70 

5.17 

5.18 

5.20 

5.14 

5.13 

5.10 

5.08 

5.06 

4.90 

4.72 

4.47 

4.35 

80 

6.62 

6.59 

6'.  54 

6.46 

6.38 

6.30 

6.26 

6.06 

5.82 

5.50 

5.33 

90 

•  • 

8.26 

8.16 

8.06 

7.97 

7.83 

7.71 

7.58 

7.30 

6.96 

6.58 

6.37 

100 

10.01 

9.87 

9.72 

9.56 

9.39 

9.21 

9.03 

8.64 

8.22 

7.76 

7.42 

NOTE. — For  temperatures  below  17.5°  C.  subtract  the  correction  and  for 
temperatures  above,  add  it. 

Ash. — METHOD  1. — Heat  5-10  grams  of  the  sample  in  a 
50-100  cc.  platinum  dish  at  100°  C.  until  water  is  expelled,  add  a 
few  drops  of  pure  olive  oil,  and  heat  slowly  over  a  flame  until 


414  TECHNICAL  METHODS  OF  ANALYSIS 

swelling  ceases.     Then  place  the  dish  in  a  muffle  and  heat  at  low 
redness  until  a  white  ash  is  obtained. 

METHOD  2. — Carbonize  the  mass  at  a  low  heat,  dissolve 
the  soluble  salts  in  hot  water,  burn  the  residual  mass  as  directed 
above,  add  the  solution  of  soluble  salts,  evaporate  to  dry  ness  at 
100°  C.,  ignite  gently,  cool  in  a  desiccator,  and  weigh. 

METHOD  3. — Saturate  the  sample  with  H2SO4,  dry,  ignite 
gently,  then  burn  in  a  muffle  at  low  redness.  Deduct  one-tenth 
of  the  weight  of  the  ash,  and  calculate  the  percentage. 

Soluble  and  Insoluble  Ash  (Tentative). — Ash  the  material  as 
directed  above  under  Method  1  or  Method  2,  add  water  to  the 
ash  in  the  dish,  heat  nearly  to  boiling,  filter,  and  wash  with  hot 
water  until  the  combined  filtrate  and  washings  are  about  60  cc. 
Return  the  filter  and  contents  to  the  dish,  ignite  carefully,  and 
weigh.  Calculate  the  percentages  of  water-soluble  and  water- 
insoluble  ash. 

Alkalinity  of  Soluble  Ash  (Tentative).— Cool  the  filtrate  from 
the  above  and  titrate  with  0. 1  N  HC1  and  methyl  orange.  Express 
the  alkalinity  as  the  number  of  cc.  of  0.1  N  acid  per  gram  of 
sample. 

Alkalinity  of  Insoluble  Ash  (Tentative). — Add  an  excess  of 
0.1  N  HC1  (usually  10-15  cc.)  to  the  ignited  insoluble  ash  in  the 
platinum  dish,  heat  to  boiling  over  an  asbestos  plate,  cool  and 
titrate  the  excess  of  HC1  with  0.1  N  NaOH  and  methyl  orange. 
Express  alkalinity  as  above. 

Mineral  Adulterants  in  the  Ash  (Tentative). — Mix  100  grams 
of  molasses,  syrup,  honey,  or  the  confectionery  solution  (prepared 
as  directed  above  under  Preparation  of  Sample  (6)),  and 
evaporate  to  a  syrupy  consistency  with  about  35  grams  of  cone. 
H2SO4  in  a  large  porcelain  evaporating  dish.  Pass  an  electric 
current  through  it  while  stirring  by  placing  one  platinum  elec- 
trode in  the  bottom  of  the  dish  near  one  side  and  attaching  the 
other  to  the  lower  end  of  the  glass  rod  with  which  the  contents 
are  stirred.  Begin  with  a  current  of  about  1  ampere  and  gradually 
increase  to  4.  In  ten  to  fifteen  minutes,  the  mass  is  reduced  to  a 
fine  dry  char,  which  may  be  readily  burnt  to  a  white  ash  in  the 
original  dish  over  a  free  flame  or  in  a  muffle. 

This  method  is  preferred  to  the  ordinary  method  of  heating 
with  H2S04,  especially  in  the  case  of  molasses,  because,  if  properly 


ANALYSIS  OF  FOODSTUFFS  415 

manipulated,  the  material  comes  quietly  into  the  form  of  a  very 
finely  divided  char  or  powder,  particularly  adapted  for  subsequent 
quick  ignition. 

If  an  electric  current  is  not  available,  treat  in  a  large  porcelain 
dish  100  grams  of  the  saccharine  solution,  evaporate  to  a  syrupy 
consistency  with  sufficient  cone.  H2&O4  to  thoroughly  carbonize 
the  mass,  and  ignite  in  the  usual  manner. 

The  following  adulterants  may  be  present:  Salts  of  tin, 
used  in  molasses  to  bleach  it;  mineral  pigments,  such  as  chromate 
of  lead  in  yellow  confectionery;  oxide  of  iron,  sometimes  used 
to  simulate  the  color  of  chocolate;  and  copper.  These  elements 
may  be  detected  by  the  usual  qualitative  tests. 

Nitrogen  (Tentative). — Determine  the  nitrogen  in  5  grams  of 
the  material  by  the  Kjeldahl,  Gunning,  or  Kjeldahl-Gunning- 
Arnold  Method  as  directed  on  pages  64-66,  using  a  larger  quantity 
of  H2S04,  if  necessary,  for  complete  digestion. 

Sucrose. — METHOD  1  (TENTATIVE). — (Substances  in  which 
the  volume  of  the  combined  insoluble  matter  and  precipitate  from 
clarifying  agents  is  less  than  1  cc.  from  26  grams.) 

Determine  sucrose  by  polarization  before  and  after  inversion 
with  HC1  as  directed  on  page  400,  under  Determination  of 
Sucrose  in  the  Absence  of  Raffinose. 

NOTE. — All  products  which  contain  dextrose  or  other  reducing  sugars  in 
the  crystalline  form,  or  in  supersaturated  solution,  exhibit  the  phenomenon 
of  birotation.  The  constant  rotation  only  should  be  employed  in  the  Clerget 
formula,  and  to  obtain  this  the  solutions  prepared  for  direct  polarization  should 
be  allowed  to  stand  overnight  before  making  the  reading.  If  it  is  desired  to 
make  the  direct  reading  immediately,  the  birotation  may  be  destroyed  by 
heating  the  neutral  solution  to  boiling  for  a  few  minutes  or  by  adding  a  few 
drops  of  cone.  NH4OH  before  completing  the  volume. 

METHOD  2. — DOUBLE  DILUTION  METHOD  (TENTATIVE.) — 
(Substances  in  which  the  volume  of  the  combined  insoluble  matter 
and  precipitate  from  clarifying  agents  is  more  than  1  cc.  from  26 
grams.) 

Weigh  out  a  half  normal  weight  (13  grams)  of  the  sample 
and  make  up  the  solution  to  100  cc.,  employing  the  appropriate 
clarifier  (basic  lead  acetate  for  dark-colored  confectionery  or 
molasses,  and  alumina  cream  for  light-colored  confectionery). 
Also  weigh  out  the  normal  weight  (26  grams)  of  the  sample  and 


416  TECHNICAL  METHODS  OF  ANALYSIS 

make  up  a  second  solution  with  the  clarifier  to  100  cc.  Filter  and 
obtain  direct  polariscopic  readings  of  both  solutions.  Invert 
each  solution  with  HC1  and  obtain  its  invert  reading. 

The  true  direct  polarization  of  the  sample  is  the  product  of  the 
two  direct  readings,  divided  by  their  difference.  The  true  invert 
polarization  is  the  product  of  the  two  invert  readings  divided  by 
their  difference.  Calculate  the  sucrose  from  the  true  polariza- 
tions thus  obtained,  by  the  formula  given  on  page  401  under 
Determination  of  Sucrose  in  the  Absence  of  Raffinose. 

Commercial  Glucose  (Approximate).  —  METHOD  1  (TEN- 
TATIVE). —  (Substances  containing  little  or  no  invert  sugar.) 

Commercial  glucose  cannot  be  determined  accurately,  owing 
to  the  varying  amounts  of  dextrin,  maltose,  and  dextrose  present. 
In  syrups,  however,  in  which  the  amount  'of  invert  sugar  is  so 
small  as  not  to  appreciably  affect  the  result,  commercial  glucose 
may  be  estimated  approximately  from  the  polarization  by  the 
following  formula: 

(o-S)  100 


in  which  G=  per  cent  of  commercial  glucose; 

a  =  direct  polarization  ; 
and  S  =  per  cent  of  cane  sugar. 

Express  results  in  terms  of  commercial  glucose  polarizing  -hi  75°  V. 

METHOD  2  (TENTATIVE).  —  (Substances  containing  invert  sugar.) 
Prepare  an  inverted  half  -normal  weight  solution  of  the  sub- 
stance as  directed  on  page  400  under  Determination  of  Sucrose 
in  the  Absence  '  of  Raffinose  by  Polarization  before  and  after 
Inversion  with  HC1,  except  that  after  inversion,  cool  the  solution, 
make  neutral  to  phenolphthalein  with  NaOH  solution,  slightly 
acidify  with  HC1,  and  treat  with  5-10  cc.  of  alumina  cream  before 
making  up  to  the  mark.  Filter  and  polarize  at  87°  C.  in  a  200 
mm.  jacketed  tube.  Multiply  the  reading  by  200  and  divide  by 
the  factor  163  to  express  the  amount  of  glucose  present  in  terms 
of  glucose  polarizing  +175°  V. 

Reducing  Sugars.  —  Determine  reducing  sugars,  either  as  dex- 
trose or  invert  sugar  by  the  Soxhlet  method  or.  Munson  and 
Walker  method  as  described  on  pages  406  and  403. 


ANALYSIS  OF  FOODSTUFFS  417 

Starch  (Tentative). — Measure  25  cc.  of  a  solution  or  uniform 
mixture,  prepared  as  directed  previously  under  Preparation  of 
Sample  (6),  which  represents  5  grams  of  sample,  into  a  300  cc. 
beaker;  or,  introduce  5  grams  of  finely  ground  sample  (previously 
extracted  with  ether  if  it  contains  much  fat)  into  the  beaker; 
add  sufficient  water  to  make  the  volume  100  cc.,  heat  to  about  60°  C. 
(avoiding,  if  possible,  gelatinizing  the  starch)  and  let  stand  for 
about  an  hour,  stirring  frequently  to  secure  complete  solution  of 
the  sugars.  Transfer  to  a  stout  wide-mouthed  bottle,  rinse  the 
beaker  with  a  little  warm  water;  cool,  add  an-  equal  volume  of 
95%  alcohol,  mix,  and  let  stand  at  least  an  hour.  Centrifuge  until 
the  precipitate  is  closely  packed  on  the  bottom  of  the  bottle 
and  decant  the  supernatant  liquid  through  a  hardened  filter. 
Wash  the  precipitate  with  successive  50  cc.  portions  of  50% 
alcohol  by  centrifuging  and  decanting  through  the  filter  until 
3  or  4  drops  of  the  washings  give  no  test  for  sugar  with  cc-naphthol 
when  treated  as  described  below.  Transfer  the  residue'  from  the 
bottle  and  the  hardened  filter  to  a  large  flask  and  determine  starch 
by  the  modified  Sachsse  method,  described  on  page  442. 

a-Naphthol  Test  for  Sucrose.— 

Introduce  into  a  test-tube  a  few  drops  of  the  liquid ;  add  4  or 
5  drops  of  20%  alcoholic  a-naphthol  solution  and  2  cc.  of  water; 
shake  well,  tip  the  tube  and  let  2-5  cc.  of  colorless  cone.  H2S04 
flow  down  the  side.  Then  hold  the  tube  upright  and,  if  sucrose 
is  present,  a  color  varying  from  a  faint  to  a  deep  violet  will  occur 
at  the  junction  of  the  two  liquids.  On  shaking  the  whole  solution 
becomes  a  blue-violet  color. 

Ether  Extract  in  Confectionery.— (A)  CONTINUOUS  EXTRACTION 
(TENTATIVE). — (1)  Measure  25  cc.  of  a  20%  mixture  or  solu- 
tion, prepared  as  directed  under  Preparation  of  Sample 
(b),  above,  in-to  a  very  thin,  readily  frangible,  glass  evaporating 
shell  (Hofmeister  Schalchen),  containing  5-7  grams  of  freshly 
ignited  asbestos  fiber;  or  (2)  if  impossible  to  obtain  a  uniform 
sample,  weigh  5  grams  of  the  mixed  finely  divided  sample  into  a 
dish,  and  wash  with  water  upon  the  asbestos  in  the  evaporating 
shell,  using,  if  necessary,  a  small  portion  of  the  asbestos  fiber  on  a 
stirring  rod  to  transfer  the  last  traces  of  the  sample  from  the  dish 
to  the  shell.  Dry  to  constant  weight  at  100°  C.,  cool,  wrap 


418  TECHNICAL  METHODS  OF  ANALYSIS 

loosely  in  smooth  paper,  crush  into  rather  small  fragments  between 
the  fingers,  transfer  carefully  the  crushed  mass,  exclusive  of  the 
paper,  to  an  extraction  tube  or  a  fat-extraction  thimble.  A 
thin  lead  disk  (bottle  cap)  may  be  substituted  for  the  Schalchen. 
The  disk  may  then  be  cut  into  small  pieces  and  placed  in  the 
extraction  tube.  Extract  with  anhydrous  ether  or  petroleum 
ether  (b.  p.  45-60°  C.  and  without  weighable  residue)  in  a  con- 
tinuous extraction  apparatus  for  at  least  twenty-five  hours.  In 
most  cases  it  is  advisable  to  remove  the  substance,  from  the 
extractor  after  the  first  twelve  hours,  grind  with  sand  to  a  fine 
powder  and  re-extract  for  the  remaining  thirteen  hours.  Trans- 
fer the  extract  to  a  tared  flask,  evaporate  the  solvent  and  dry  to 
constant  weight  in  an  oven  at  100°  C. 

(B)    ROESE-GOTTLIEB       METHOD        (TENTATIVE). Substances 

such  as  butter-scotch,  invariably  yield  extremely  inaccurate  results 
by  the  above  method.  In  such  cases  introduce  4  grams  of  the 
material,  or  an  amount  of  a  uniform  solution  equivalent  to  this 
amount  of  the  dry  substance,  into  a  Rohrig  tube  or  similar  appa- 
ratus, make  up  to  a  volume  of  10  cc.  with  water,  add  1.25  cc.  of 
cone.  NH40H  and  mix  thoroughly.  Add  10  cc.  of  95%  alcohol 
and  mix.  Then  add  25  cc.  of  washed  ether  and  shake  vigorously 
for  half  a  minute;  then  add  25  cc.  of  petroleum  ether  (b.  p.  below 
60°  C.),  and  shake  again  for  half  a  minute.  Let  stand  twenty 
minutes,  or  until  separation  between  the  liquids  is  complete. 
Draw  off  as  much,  as  possible  of  the  ether-fat  solution  (usually 
0.5-0.8  cc.  will  be  left)  into  a  weighed  flask  through  a  small,  rapid 
filter.  (The  flask  should  be  weighed  with  a  similar  one  as  a 
counterpoise.)  Again  extract  the  liquid  remaining  in  the  tube, 
this  time  with  15  cc.  each  of  ether  and  petroleum  ether,  shake 
vigorously  half  a  minute  with  each,  and  let  settle.  Proceed  as 
above  washing  the  tip  of  the  spigot  and  the  filter  with  a  few  cc. 
of  a  mixture  of  equal  parts  of  the  2  ethers  (previously  mixed  and 
free  from  deposited  water).  For  absolutely  exact  results  the 
extraction  must  be  repeated.  This  third  extraction  usually  yields 
not  more  than  about  1  mg.  of  fat,  if  the  previous  ether-fat  solutions 
have  been  drawn  off  closely,  or  an  amount  averaging  about  0.02% 
on  a  4-gram  charge.  Evaporate  the  ether  slowly  on  a  steam  bath, 
then  dry  the  fat  in  a  boiling  water  oven  to  con t ant  weight. 

Test  the  purity  of  the  fat  by  dissolving  in  a  little  petroleum 


ANALYSIS  OF  FOODSTUFFS  419 

ether.  Should  a  residue  remain,  wash  the  fat  out  completely  with 
petroleum  ether,  dry  the  residue,  weigh  and  deduct  the  weight. 

Paraffin  in  Confectionery  (Tentative). — Add  to  the  ether 
extract  in  the  flask,  as  above  obtained,  10  cc.  of  95%  alcohol  and 
2  cc.  of  NaOH  solution  (1  :  1);  connect  the  flask  with  a  reflux 
condenser,  and  heat  for  one  hour  on  the  water  bath,  or  until 
saponification  is  complete.  Remove  the  condenser  and  let  the 
flask  remain  on  the  bath  until  alcohol  is  evaporated  and  the 
residue  is  dry.  Dissolve  the  residue  as  completely  as  possible 
in  about  40  cc.  of  water  and  heat  on  the  bath,  shaking  frequently. 
Wash  into  a  separatory  funnel,  cool,  and  extract  with  four  suc- 
cessive portions  of  petroleum  ether,  which  are  collected  in  a  tared 
flask  or  capsule.  Evaporate  the  petroleum  ether  and  dry  in  the 
oven  to  constant  weight. 

Any  phytosterol  or  cholesterol  present  in  the  fat  would  be 
extracted  with  the  paraffin.  The  amount  is  so  insignificant 
that  it  may  be  disregarded  generally.  The  character  of  the 
final  residue  should,  however,  be  confirmed  by  determining  its 
melting  point,  sp.  gr.,  and  refractive  index. 

Alcohol  in  Syrups  used  in  Confectionery  ("  Brandy  Drops  ") 
(Tentative). — Collect  in  a  beaker  the  syrup  from  a  sufficient 
number  of  pieces  to  yield  30-50  grams  of  syrup.  Strain  into  a 
tared  beaker  and  weigh.  Introduce  the  syrup  into  a  250-300  cc. 
distilling  flask,  dilute  with  half  its  volume  of  water,  attach  the 
flask  to  a  vertical  condenser  and  distill  almost  50  cc.  or  as  much  of 
the  liquid  as  possible  without  causing  charring.  Foaming  may 
be  prevented  by  adding  a  little  tannin  or  a  piece  of  paraffin 
about  the  size  of  a  pea  to  the  contents  of  distillation  flask.  Cool 
the  distillate,  make  up  to  volume  with  water,  mix  well,  determine 
the  sp.  gr.  of  the  liquid  very  carefully  with  a  pycnometer  at 
standard  temperature  and  obtain  the  corresponding  weight  of 
alcohol  in  the  50  cc.  of  distillate  from  standard  alcohol  tables.* 
Calculate  the  per  cent  by  weight  of  alcohol  in  the  candy  filling. 

Coloring  Matter. — Proceed  as  under  Coloring  Matter  in 
Foods,  page  389. 

*  These  tables  may  be  found  in  J.  Assoc.  Official  Agr.  Chemists,  Methods 
of  Analysis,  (1916),  pages  194-207;  also  Leach:  "  Food  Inspection  and 
Analysis,"  3d  Edition,  pages  661-674;  and  Van  Nostrand's  "  Chemical 
Annual."  * 


420  TECHNICAL   METHODS  OF  ANALYSIS 

REFERENCE. — J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis  (1916), 
pages  121-132. 


HONEY 

General. — The  following  methods,  unless  otherwise  indicated, 
are  the  tentative  methods  of  the  Association  of  Official  Agricul- 
tural Chemists.* 

Preparation  of  Sample. — (a)  LIQUID  OR  STRAINED  HONEY. — 
If  the  sample  is  free  from  granulation,  mix  thoroughly  by  stirring 
or  shaking  before  drawing  the  weighed  portions  for  analysis.  If 
the  honey  is  granulated,  place  the  container,  with  the  stopper 
loose,  in  a  water  bath,  and  heat  at  not  over  50°  C.  until  the  sugar 
crystals  dissolve;  mix  thoroughly,  cool,  and  weigh  out  portions 
for  analysis.  If  sediment  is  present,  su'ch  as  particles  of  comb, 
wax,  sticks,  bees,  etc.,  heat  the  sample  to  40°  C.  in  a  water  bath 
and  filter  through  cheesecloth  before  weighing. 

(6)  COMB  HONEY. — Cut  across  the  top  of  the  comb,  if  sealed, 
and  separate  completely  from  the  comb  by  straining  through  a  40- 
mesh  sieve.  If  portions  of  the  comb  or  wax  pass  through  the  sieve, 
heat  the  sample  as  in  (a)  and  strain  through  a  cloth.  If  the  honey 
is  granulated  in  the  comb,  heat  until  the  wax  is  liquefied,  stir,  cool, 
remove  the  wax  and  take  the  clear  liquid  for  analysis. 

Moisture. — Weigh  2  grams  into  a  tared,  flat-bottomed,  plat- 
inum, or  aluminum  dish  of  about  60  mm.  diameter  and  containing 
10-15  grams  of  fine  quartz  sand  (which  has  been  previously 
washed,  dried  and  ignited)  and  a  small  glass  stirring  rod;  add 
5-10  cc.  of  water  and  thoroughly  incorporate  it  with  the  sand  and 
honey  mixture  by  means  of  the  rod;  dry  the  dish  and  contents 
to  constant  weight  in  a  vacuum  oven  at  not  over  70°  C. 

Ash  (Official). — Weigh  5-10  grams  into  a  weighed  platinum 
dish,  add  a  few  drops  of  pure  olive  oil  to  prevent  spattering  and 
heat  carefully  till  swelling  ceases  and  then  ignite  to  a  white  ash 
at  not  above  dull  redness. 

Soluble  and  Insoluble  Ash. — Add  water  to  the  ash  in  the  plat- 
inum dish,  heat  nearly  to  boiling,  filter  through  an  ashless  filter 
paper,  and  wash  with  hot  water  until  the  combined  filtrate  and 

*See  J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis  (1916), 
page  133. 


ANALYSIS  OF  FOODSTUFFS  421 

washings  measure  about  60  cc.  Return  filter  paper  and  contents 
to  the  dish,  ignite  carefully,  and  weigh.  Calculate  the  percentages 
of  water-soluble  and  water-insoluble  ash. 

Alkalinity  of  Soluble  Ash. — Cool  the  filtrate  from  the  above 
determination  and  titrate  with  0.1  N  HC1  and  methyl  orange. 
Express  alkalinity  in  terms  of  cc.  of  0.1  N  acid  per  gram  of  the 
sample. 

Polarization. — I.  DIRECT  POLARIZATION. — (a)  Immediate  direct 
polarization. — Transfer  26  grams  of  the  honey  to  a  100  cc.  volu- 
metric flask  with  water,  add  5  cc.  of  alumina  cream,  dilute  to  the 
mark  with  water  at  20°  C.,  filter  and  polarize  immediately  in  a 
200  mm.  tube. 

(6)  Constant  direct  polarization. — Pour  the  solution  from  the 
tube  used  in  reading  (a)  back  into  the  flask,  stopper,  and  let  stand 
twenty-four  hours.  Then  again  polarize  the  solution  at  20°  C. 
in  a  200  mm.  tube. 

(c)  Birotation. — The  difference  between  (a)  and  (6)  gives  the 
birotation. 

(d)  Direct  polarization  at  87°  C. — Polarize  the  solution  obtained 
in  (b)  at  87°  C.  in  a  jacketed  200  mm.  tube. 

II.  INVERT  POLARIZATION.— (a)  At  20°  C.— Invert  with  HC1 
50  cc.  of  the  solution  (obtained  under  Direct  Polarization  above) 
as  described  on  page  400  under  the  determination  of  Sucrose 
in  the  Absence  of  Raffinose,  and  polarize  at  20°  C.  in  a  200  mm. 
tube. 

(6)  At  87°  C.— Polarize  the  above  solution  also  at  87°  C. 
in  a  200  mm.  jacketed  tube. 

Reducing  Sugars. — Dilute  10  cc.  of  the  solution  used  for  direct 
polarization  to  250  cc.  Pipette  out  25  cc.  and  determine  the 
reducing  sugars  by  the  Munson  and  Walker  or  the  Allihn  method 
as  described  on  pages  403  and  407  and  calculate  the  result  to  per 
cent  of  invert  sugar. 

Sucrose. — Take  10  cc.  of  the  solution  obtained  for  invert 
polarization,  dilute  with  a  small  amount  of  water,  neutralize 
with  Na2COs,  and  make  up  to  250  cc.  with  water.  Pipette  50  cc. 
of  this  solution  and  determine  the  total  sugars  as  reducing  sugars 
by  the  Munson  and  Walker  method.  Calculate  to  invert  sugar. 
Deduct  the  per  cent,  of  invert  sugar  obtained  previously  and  mul- 
tiply the  difference  by  0.95.  The  result  is  the  per  cent  of  sucrose. 


422  TECHNICAL  METHODS  OF  ANALYSIS 

Levulose. — Multiply  the  direct  polarization  reading  at  '87°  C. 
by  1.0315  and  subtract  the  product  from  the  constant  direct 
polarization  at  20°  C.;  divide  the  difference  by  2.3919  to  obtain 
the  grams  of  levulose  in  the  normal  weight  (26  grams)  of  honey. 
From  this  figure  calculate  the  per  cent  in  the  original  sample. 

Dextrose. — Subtract  the  per  cent  of  levulose  above  determined 
from  the  per  cent  of  invert  sugar  found  under  Reducing  Sugars, 
to  obtain  the  approximate  per  cent  of  dextrose. 

The  dextrose  can  be  determined  more  accurately  by  multi- 
plying the  per  cent  of  levulose  by  the  factor  0.915,  which  gives  its 
dextrose  equivalent  in  copper  reducing  power.  Subtract  this 
figure  from  that  of  the  reducing  sugars  calculated  as  dextrose,  to 
obtain  the  per  cent  of  dextrose  in  the  sample. 

NOTE.— Owing  to  the  difference  in  the  reducing  powers  of  different  sugars, 
the  sum  of  the  dextrose  thus  found  and  the  levulose  as  calculated  above  will 
be  greater  than  the  total  amount  of  invert  sugar  obtained  under  Reducing 


Dextrin  (Approximate). — Transfer  8  grams  of  sample  (4 
grams  in  the  case  of  dark-colored  honey-dew  honey)  to  a  100  cc. 
volumetric  flask  (using  not  more  than  4  cc.  of  water)  by  letting  the 
sample  drain  from  the  weighing  dish  into  the  flask  and  then  dis- 
solving the  residue  in  2  cc.  of  water.  After  adding  this  solution 
to  the  contents  of  the  flask,  rinse  the  weighing  dish  with  two  1  cc. 
portions  of  water  to  which  a  little  alcohol  is  added  subsequently. 
Fill  the  flask  to  the  mark  with  absolute  alcohol,  shaking  con- 
stantly. Set  the  flask  aside  until  the  dextrin  has  collected  on  the 
sides  and  bottom  and  the  liquid  is  clear.  Decant  the  clear  liquid 
through  a  filter  paper  and  wash  the  residue  in  the  flask  with 
10  cc.  of  95%  alcohol,  pouring  the  washings  through  the  same 
filter.  Dissolve  the  dextrin  in  the  flask  with  boiling  water  and 
filter  through  the  filter  paper  already  used,  receiving  the  filtrate 
in  a  tared  dish,  prepared  as  follows :  Digest  pure  quartz  sand  with 
strong  HC1,  wash,  dry  and  ignite.  Place  6-7  grams  of  the  pre- 
pared sand  and  a  short  stirring  rod  in  the  dish.  Dry  thoroughly, 
cool  in  a  desiccator  and  weigh. 

Rinse  the  flask  and  wash  the  filter  several  times  with  small 
portions  of  hot  water,  add  the  washings  to  the  tared  dish,  and 
evaporate  the  whole  on  a  water  bath.  Dry  to  constant  weight 
in  vacuo  at  70°  C. 


ANALYSIS  OF  FOODSTUFFS  423 

After  determining  the  weight  of  the  alcoholic  precipitate,  dis- 
solve the  latter  in  water  and  make  up  to  volume,  using  50  cc. 
of  water  for  each  0.5  gram  of  precipitate  or  part  thereof. 

Determine  the  reducing  sugars  in  the  solution,  both  before  and 
after  inversion,  by  the  Munson  and  Walker  method,  expressing 
results  as  invert  sugar.  Calculate  the  sucrose  from  the  results 
thus  obtained  and  subtract  the  sum  of  the  reducing  sugars  before 
inversion  and  of  the  sucrose  from  the  weight  of  the  total  alcoholic 
precipitate  to  obtain  the  weight  of  the  dextrin. 

Free  Acid. — Dissolve  10  grams  of  honey  in  water  and  titrate 
with  0.1  N  NaOH  and  phenolphthalein.  Express  results  in  terms 
of  cc.  of  0.1  N  NaOH  required  to  neutralize  100  grams  of  the 
sample. 

Glucose.  —QUALITATIVE  TEST. — Dilute  the  honey  with  an  equal 
volume  of  water,  then  add  a  few  cc.  of  iodine  solution  (1  gram  of 
iodine,  3  grams  of  KI,  50  cc.  of  water).  In  the  presence  of  glucose 
the  solution  turns  red  or  violet,  the  depth  and  character  of  the 
color  depending  upon  the  quality  and  nature  of  the  glucose  em- 
ployed. A  blank  test  with  a  pure  honey  of  about  the  same  color 
should  be  made  in  order  to  secure  an  accurate  color  comparison. 
Should  the  honey  be  dark  and  the  percentage  of  glucose  very 
small,  precipitate  the  dextrin  which  may  be  present  by  adding 
several  volumes  of  95%  alcohol.  Let  stand  until  the  precipitate 
settles  (do  not  filter),  decant  the  liquid,  dissolve  the  residue  of 
dextrin  in  hot  water,  cool  and  apply  the  above  test  to  this  solution. 
A  negative  result  is  not  proof  of  the  absence  of  glucose,  as  some 
glucose,  especially  of  high  conversion,  does  not  give  any  reaction 
with  iodine. 

QUANTITATIVE  TEST. — An  approximate  determination  can  be 
made  by  Browne's  formula  as  follows:  Multiply  the  difference 
in  the  polarizations  of  the  invert  solution  at  20°  C.  and  at  87°  C. 
by  77  and  divide  this  product  by  the  per  cent  of  invert  sugar 
after  inversion  found  in  the  sample.  Multiply  the  quotient  by 
100  and  divide  the  product  by  26.7,  to  obtain  the  per  cent  of  honey 
in  the  sample;  100  per  cent  minus  per  cent  of  honey  gives  per  cent 
of  glucose. 

Commercial  Invert  Sugar. — (A)  BRYAN'S  MODIFICATION  OF 
FIBRE'S  QUALITATIVE  TEST. — Dissolve  1  gram  of  resorcinol  in 
100  cc.  of  cone.  HC1.  Introduce  10  cc.  of  50%  honey  solution  into 


424  TECHNICAL  METHODS  OF  ANALYSIS 

a  test  tube  and  add  5  cc.  of  ether.  Shake  gently  and  let  stand 
for  some  time  until  the  ether  layer  is  clear.  Transfer  2  cc.  of 
this  clear  ether  solution  to  a  small  test  tube  and  add  a  large  drop 
of  the  resorcinol  solution.  Shake  and  note  the  color  immediately. 
In  the  presence  of  artificial  invert  sugar,  the  resorcinol  assumes 
immediately  an  orange-red  color,  turning  to  dark  red. 

(B)  FEDER  ANILINE  CHLORIDE  TEST. — To  100  cc.  of  c.  P. 
aniline  add  30  cc.  of  25%  HC1.  Introduce  5  grams  of  the  honey 
into  a  porcelain  dish  and  add  2.5  cc.  of  the  aniline  reagent.  A 
bright  red  color  indicates  the  presence  of  commercial  invert 
sugar. 

Diastase. — Mix  1  part  of  honey  with  2  parts  of  sterile  water. 
Treat  10  cc.  of  this  solution  with  1  cc.  of  1%  soluble  starch  solu- 
tion and  digest  at  45°  C.  for  an  hour.  At  the  end  of  this  time 
test  the  mixture  with  1  cc.  of  iodine  solution  (1  gram  of  iodine, 
2  grams  of  KI,  300  cc.  of  water).  Treat  another  10  cc.  portion  of 
the  honey  solution,  mixed  with  1  cc.  of  the  soluble  starch  solution, 
without  heating  to  45°  C.,  with  the  reagent  and  compare  the  colors 
produced.  If  the  original  honey  had  not  been  heated  sufficiently 
to  kill  the  diastase,  an  olive-green  or  brown  coloration  will  be 
produced  in  the  mixture  that  has  been  heated  at  45°  C.  Heated 
or  artificial  honey  becomes  blue. 


MAPLE  PRODUCTS 

General. — The  procedures  given  herewith  (unless  otherwise 
indicated)  are  the  tentative  methods  of  the  Association  of  Official 
Agricultural  Chemists.* 

Preparation  of  Sample. — (A)  MAPLE  SYRUP. — Determine  the 
moisture  as  given  below.  If  it  is  less  than  35%  and  there  is  some 
mineral  sediment,  pour  the  clear  syrup  into  a  beaker,  washing  the 
sediment  also  into  the  beaker  with  water.  Then  concentrate 
the  syrup  by  boiling  to  a  moisture  content  of  about  35%  (b.  p. 
104°  C.).  Set  aside  until  cool,  or  preferably  let  the  covered 
material  stand  overnight,  and  pour  off  the  clear  liquid  for  the 
analytical  work.  Where  no  sediment  is  present,  the  sample 

*  See  J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis  (1916),  page 
136. 


ANALYSIS  OF  FOODSTUFFS  425 

is  ready  for  analysis  after  careful  mixing.  Where  sugar  has 
crystallized  out,  warm  to  dissolve  the  sugar  before  starting  the 
analysis.  It  is  desirable,  in  order  to  compare  results  upon  dif- 
ferent samples,  to  reduce  all  results  other  than  moisture  to  a  dry 
substance  basis  as  determined  in  the  clear  syrup. 

(B)  MAPLE    SUGAR,    MAPLE    CREAM,  ETC. — Determine    the 
moisture  as  described  below  in  the  sample  in  its  original  condition 
by  thoroughly  mixing,  if  semi-plastic,  or  by  rubbing  up  in  a  mortar 
representative  portions  of  the  product,  if  solid.     For  all  other 
analytical   determinations   use   a  solution   prepared   as  follows: 
Weigh  roughly  100  grams  of  the  product  into  a  beaker  and  dissolve 
by  boiling  with  200  cc.  of  water.     Decant  the  resulting  syrup 
while  hot  through  a  muslin  filter,  concentrate  by  boiling  to  a 
moisture  content  of  35%  (b.  p.  104°  C.);   cool,  or  preferably  let 
the  covered  material  stand  overnight;  set  aside  until  clear,  and 
use  this  clear  syrup  for  analysis.     It  is  desirable,  in  order  to  com- 
pare results  upon  different  samples,  that  all  results  except  moisture 
be  expressed  upon  the  dry  basis. 

Moisture. — Weigh  2  grams  of  the  sample  into  a  tared  flat- 
bottom  platinum  dish  having  a  diameter  of  about  60  mm.  and  con- 
taining 10-15  grams  of  fine  quartz  sand  which  has  been  pre- 
viously washed,  dried  and  ignited,  and  a  small  glass  stirring  rod. 
Add  5-10  cc.  of  water  and  incorporate  thoroughly  with  the  sand 
and  syrup  or  sugar  mixture  by  means  of  the  rod.  Dry  the  dish 
and  contents  to  constant  weight  in  a  vacuum  oven  at  a  tem- 
perature not  exceeding  70°  C. 

Polarization.— (A)  DIRECT  AT  20°  C.;  (B)  INVERT  AT  20°  C.— 
Make  these  determinations  as  described  under  the  determination 
of  Sucrose  in  the  Absence  of  Raffinose  by  Polarization  before  and 
after  Inversion  with  HC1,  page  400. 

(C)  INVERT  AT  87°  C. — Proceed  as  described    under  Com- 
mercial Glucose,  Method  2,  on  page  416. 

Reducing  Sugars  as  Invert  Sugar. — (A)  BEFORE  INVERSION. — 
Proceed  as  directed  on  page  403,  using  the  Munson  and  Walker 
method.  Employ  an  aliquot  of  the  solution  used  for  the  direct 
polarization  (as  above)  and  use  only  neutral  lead  acetate  for  clar- 
ification. 

(B)  AFTER  INVERSION. — Proceed  as  above,  using  an  aliquot  of 
the  solution  used  for  the  invert  polarization. 


426  TECHNICAL  METHODS  OF  ANALYSIS 

Sucrose. — (A)  BY  POLARIZATION. — Proceed  as  described  on 
page  400  under  the  determination  of  Sucrose  in  the  Absence  of 
Raffinose  by  Polarization  before  and  after  Inversion  with  HC1. 

(B)  REDUCING  SUGARS  BEFORE  AND  AFTER  INVERSION. — 
Follow  the  Munson  and  Walker  procedure  on  page  403,  clarifying 
with  neutral  lead  acetate. 

Total  Ash. — Follow  the  procedure  on  page  413. 

Soluble  and  Insoluble  Ash. — See  page  414. 

Alkalinity  of  Soluble  and  Insoluble  Ash. — See  page  414. 

Lead  Number  (Winton). — (A)  REAGENT:  Standard  Basic  Lead 
Acetate  Solution. — Boil  430  grams  of  normal  lead  acetate  and 
130  grams  of  PbO  (or  560  grams  of  Home's  dry  basic  lead  acetate) 
for  thirty  minutes,  with  1  liter  of  water,  cool,  let  settle  and  dilute 
the  supernatant  liquid  to  sp.  gr.  1.25.  To  a  measured  amount  of 
this  solution  add  four  volumes  of  water  and  filter  if  not  perfectly 
clear.  The  solution  should  be  standardized  each  time  a  set  of 
determinations  is  made.  If  the  directions  for  preparing  the  basic 
lead  acetate  are  not  carried  out  carefully,  the  use  of  Home's 
dry  basic  lead  acetate  is  preferable. 

(B)  DETERMINATION  OF  LEAD  IN  THE  BLANK. — Transfer  25  cc. 
of  the  standard  basic  lead  acetate  to  a  100  cc.  flask,  add  a  few 
drops  of  acetic  acid  and  make  up  to  the  mark  with  water.     Shake 
and  determine  Pb  as  PbS04  in  10  cc.  of  the  solution,  as  directed 
below.     The  use  of  the  acid  is  imperative  in  this  case  to  keep  the 
lead  in  solution  when  diluted  with  water. 

(C)  DETERMINATION. — Transfer  25  grams  of  the  sample  to  a 
100  cc.  flask  by  means  of  water.     Add  25  cc.  of  the  standard  basic 
lead  acetate  and  shake;  fill  to  the  mark,  shake  and  let  stand  for 
at  least  three  hours  before  filtering.     Pipette  10  cc.  of  the  clear 
filtrate  into  a  250  cc.  beaker,  add  40  cc.  of  water  and  1  cc.  of  cone. 
H2SO4,  shake  and  add  100  cc.  of  95%  alcohol.     Let  stand  over- 
night, filter  on  a  tared  Gooch  crucible,  wash  with  95%  alcohol, 
dry  in  a  water  oven,  and  ignite  in  a  muffle  or  over  a  Tirrill  burner. 
Apply  the  heat  gradually  at  first,  and  if  a  flame  is  used,  set  the 
Gooch  crucible  inside  of  a  platinum  crucible.     Cool  and  weigh. 
Subtract  the  weight  of  PbSC>4  so  found  from  the  weight  of  PbSO4 
found  in  the  blank  above  and  multiply  by  the  factor  27.325.    The 
use  of  this  factor  gives  the  lead  number  directly  without  the  vari- 
ous calculations  otherwise  required. 


ANALYSIS  OF  FOODSTUFFS  427 

Malic  Acid  Value  (Cowles  Method). — Weigh  6.7  grams  of  the 
sample  into  a  200  cc.  beaker,  add  5  cc.  of  water,  then  2  cc.  of  a  10% 
calcium  acetate  solution  and  stir.  Add  gradually,  and  with 
constant  stirring,  100  cc.  of  95%  alcohol,  and  agitate  the  solution 
until  the  precipitate  settles;  or  let  stand  until  the  supernatant 
liquid  is  clear.  Filter  off  the  precipitate  and  wash  with  75  cc. 
of  85%  alcohol.  Dry  the  filter  paper  and  ignite  in  a  platinum 
dish.  Add  10  cc.  of  0.1  N  HC1  and  warm  gently  until  all  the  lime 
dissolves.  Cool  and  titrate  back  with  0.1  N  NaOH  and  methyl 
orange.  The  difference  in  cc.  divided  by  10  represents  the  malic 
acid  value  of  the  sample.  Previous  to  use  the  reagents  should 
be  tested  by  a  blank  determination  and  any  necessary  corrections 
applied. 

BUTTER  AND   BUTTER  SUBSTITUTES 
(BUTTERINE,   OLEOMARGARINE,  ETC.) 

General. — Butter  fat  is  the  fat  of  milk  or  butter.  It  has  a 
peculiar  and  complex  composition,  the  characteristic  constituent 
being  the  radicle  of  butyric  acid.  Butter  consists  of  a  mixture 
of  about  80-90%  of  butter  fat  with  variable  proportions  of  water, 
curd  and  salt.  Coloring  matter  is  often  added  and  Na2COs 
is  sometimes  employed  to  prevent  rancidity.  In  the  United 
States  the  legal  title  for  all  butter  substitutes  is  Oleomargarine 
(in  England  and  several  other  countries  it  is  Margarine).  In 
preparing  these  substitutes  various  fats  are  used,  including  lard 
and  tallow.  The  proper  consistency  is  often  obtained  by  adding 
sesame,  peanut  or  cottonseed  oil.  The  fat  is  then  usually  incor- 
porated with  milk  and  salt,  and  colored.  Sometimes  more  or 
less  real  butter  is  added;  and  palm  oil  and  purified  cocoanut  oil 
have  also  been  used. 

Preparation  of  Sample. — If  large  quantities  of  butter  are  to  be 
sampled,  use  butter  trier  or  sampler.  Melt  completely  the  por- 
tions thus  drawn,  100-150  grams,  in  a  closed  vessel  at  as  low  a 
temperature  as  possible  and,  when  melted,  shake  the  whole 
violently  for  some  minutes,  cooling  at  the  same  time,  until  the 
mass  is  homogeneous  and  sufficiently  solidified  to  prevent  the 
separation  of  the  water  and  fat.  Then  pour  a  portion  into  the 
vessel  from  which  it  is  to  be  weighed  for  analysis.  It  should 


428  TECHNICAL  METHODS  OF  ANALYSIS 

nearly  or  quite  fill  the  vessel  and  should  be  kept  in  a  cool  place 
until  analyzed. 

Moisture. — Place  1.5-2.5  grams  in  a  dish  with  a  flat  bottom 
having  a  surface  of  at  least  20  sq.  cm.,  dry  at  the  temperature  of 
boiling  water  and  weigh  hourly  until  it  ceases  to  lose  weight. 
The  use  of  clean  dry  sand  or  asbestos  is  admissible.  . 

Fat  (Ether  Extract). — (a)  INDIRECT  METHOD. — Dissolve  in 
the  dish  with  absolute  ether  or  petroleum  ether  the  dry  butter 
obtained  in  the  moisture  determination  (in  which  no  absorbent  was 
used),  transfer  to  a  weighed  Gooch  crucible  with  the  aid  of  a  wash 
bottle  filled  with  the  solvent  and  wash  until  free  from  fat.  Dry 
the  crucible  and  contents  at  the  temperature  of  boiling  water 
until  the  weight  is  constant  and  calculate  the  fat  by  difference. 

(6)  DIRECT  METHOD. — From  the  dry  butter  obtained  in  deter- 
mining the  moisture,  either  wither  without  the  use  of  an  absorbent, 
extract  the  fat  with  anhydrous  alcohol-free  ether,  receiving  the 
solution  in  a  weighed  flask.  v  Evaporate  the  ether,  dry  the  extract 
at  the  temperature  of  boiling  water,  and  weigh  hourly  until  it 
ceases  to  lose  weight. 

Casein,  Ash,  and  Chlorine. — Cover  the  crucible  containing 
the  residue  from  the  fat  determination  by  the  Indirect  Method 
(a)  above  and  heat,  gently  at  first,  gradually  raising  the  temper- 
ature to  just  below  redness.  The  cover  may  then  be  removed  and 
the  heat  continued  until  the  contents  of  the  crucible  are  white.  The 
loss  in  weight  represents  casein,  and  the  residue  in  the  crucible 
mineral  matter.  In  this  mineral  matter,  dissolved  in  water 
slightly  acidulated  with  HNOs,  determine  chlorine  either  gravi- 
metrically  or  volumetrically. 

Salt. — Weigh  in  a  counterpoised  beaker  5-10  grams  of  the 
material,  using  portions  of  about  1  gram  from  different  parts 
of  the  sample.  Add  about  20  cc.  of  hot  water  and,  after  it  is 
melted,  transfer  the  whole  to  a  separatory  funnel.  Insert  the 
stopper  and  shake  for  a  few  minutes.  Let  stand  until  the  fat 
has  all  collected  on  top  of  the  water,  then  draw  off  the  latter  into 
a  flask,  being  careful  to  let  none  of  the  fat  globules  escape.  Again 
add  hot  water  to  the  beaker  and  repeat  the  extraction  10-15 
times,  using  each  time  10-20  cc.  of  water.  The  washings  will 
contain  all  but  a  mere  trace  of  the  NaCl  originally  present  in  the 
butter.  Determine  its  amount  in  the  whole  or  an  aliquot  of  the 


ANALYSIS  OF  FOODSTUFFS  429 


liquid  by  the  volumetric  AgNOs  method  with  K^CrCU  as  indi- 
cator. 

CALCULATION.—  1  cc.  0.1  N  AgNO3  =  0.00585  gram  Nad. 

Examination  of  Fat.  —  (a)  PREPARATION  OF  SAMPLE.  —  Melt 
the  butter  and  keep  it  in  a  dry  place  at  about  60°  C.  for  two  or 
three  hours,  until  the  water  and  curd  have  entirely  separated. 
Filter  the  clear  supernatant  fat  through  a  dry  filter  paper  in  a  hot- 
water  funnel  or  in  an  oven  at  about  60°  C.  Should  the  filtered 
liquid  fat  not  be  perfectly  clear,  it  must  be  refiltered. 

(6)  REICHERT-MEISSL  NUMBER.  —  Determine  the  Reichert- 
Meissl  number  as  described  under  Animal  and  Vegetable  Oils, 
page  243. 

(c)  SPECIFIC  GRAVITY.  —  Determine  with  a  pycnometer  the 
sp.  gr.  at  40°  C.  compared  with  water  at  the  same  temperature. 

NOTES.  —  (1)  The  average  Reichert-Meissl  number  of  pure  butter  fat  is 
26.  To  calculate  the  approximate  amount  of  butter  fat  in  a  butter  sub- 
stitute, divide  the  Reichert-Meissl  number  of  the  separated  fat  by  26  and 
multiply  by  the  percentage  of  total  fat  in  the  butter  substitute. 

(2)  U.  S.  Standard  for  Butter:  It  shall  contain  not  less  than  82.5%  of 
butter  fat. 

U.  S.  Standard  for  Butter  Fat:    It  shall  have  a  Reichert-Meissl  number 

40°  C 
of  not  less  than  24  and  the  sp.  gr.  at  4QO  c  shall  be  not  less  than  0.905. 

Renovated  Butter  and  Oleomargarine.  —  (a)  FOAM  TEST 
(SPOON  TEST)  —  Heat  2-3  grams  of  the  sample,  either  in  a  spoon  or 
a  dish,  over  a  free  flame.  True  butter  foams  abundantly,  whereas 
process  butter  will  bump  and  sputter  without  foaming.  Oleo- 
margarine behaves  like  process  butter,  but  the  chemical  tests 
will  determine  whether  the  sample  is  oleo  or  butter.  • 

(6)  MELTED  FAT  TEST.  —  Melt  50-100  grams  of  the  sample 
at  50°  C.  The  curd  from  butter  will  settle,  leaving  a  clear  super- 
natant fat;  with  renovated  butter,  the  supernatant  fat  remains 
more  or  less  turbid. 

NOTES.  —  (1)  For  the  examination  of  butter  for  artificial  coloring,  see 
Leach:  "  Food  Inspection  and  Analysis." 

(2)  The  above  methods  are  those  of  the  Association  of  Official  Agricultural 
Chemists. 


430  TECHNICAL  METHODS  OF  ANALYSIS 


COCOA,  CHOCOLATE  AND  CACAO  PRODUCTS 

General. — Plain  or  bitter  chocolate  (chocolate  liquor)  accord- 
ing to  the  Federal  Standard  (Bureau  of  Chemistry,  Circular  19) 
is  the  solid  or  plastic  mass  obtained  by  grinding  cacao  nibs  without 
the  removal  of  fat  or  other  constituents,  except  the  germs;  and 
contains  not  over  3%  of  ash  insoluble  in  water,  3.5%  of  crude 
fiber,  9%  of  starch,  and  not  less  than  45%  of  cocoa  fat.*  By 
extraction  of  part  of  the  fat  cocoa  is  obtained.  The  fat  in  cocoa 
generally  runs  from  18  to  24%. 

Sweetened  chocolate  is  made  by  adding  sucrose  (and  some- 
times cocoa  butter,  spices,  etc.)  to  bitter  chocolate,  and  according 
to  Bureau  of  Chemistry,  Circular  19,  it  should  contain,  on  a  sugar 
and  fat-free  basis,  no  higher  percentage  of  either  ash,  fiber,  or 
starch  than  is  found  in  the  sugar  and  fat-free  residue  of  bitter 
chocolate. 

Chocolate  is  further  modified  by  the  addition  of  milk  or 
milk  solids  and  is  sold  as  "  Milk  Chocolate/'  either  sweetened 
or  unsweetened.  According  to  Food  Inspection  Decision  136, 
both  sweetened  and  unsweetened  milk  chocolates  should  contain 
at  least  12%  of  milk  solids.  (For  determination  see  page  427.) 

For  direct  comparison  of  different  kinds  of  chocolate  and 
cocoa  it  is  best  to  convert  the  results  of  analysis  to  a  "  moisture-, 
fat-,  and  sugar-free  basis."  This  is  accomplished  by  dividing 
the  analytical  figures  by  1 — (M-f-F+S),  where  M,  F,  and  S  are 
the  percentages  of  moisture,  fat  and  sugar,  respectively,  each 
expressed  as  a  decimal. 

The  following  procedures  where  marked  Official  or  Tentative 
are  those  of  the  Association  of  Official  Agricultural  Chemists. 

Preparation  of  Sample  (Tentative). — Mix  powdered  products 
thoroughly  and  preserve  in  tightly  stoppered  bottles.  Chill  sweet 
or  bitter  chocolate  until  hard  and  reduce  to  a  finely  granular 
condition  by  grating  or  shaving.  Mix  thoroughly  and  preserve 
in  a  tightly  stoppered  bottle  in  a  cool  place. 

Moisture  (Official). — Dry  about  2  grams  in  a  flat  dish  (prefer- 
ably platinum,  although  nickel  or  aluminum  is  allowable)  at  the 

*  To  convert  the  analysis  of  a  cocoa  or  chocolate  to  the  "45%  fat  basis," 

multiply  the  analytical  results  by  — — — — ,  where  F=  %  fat  found  by  analysis. 

100  —  r . 


ANALYSIS  OF  FOODSTUFFS  431 

temperature  of  boiling  water  for  ten  hours.  Cool  in  desiccator 
and  weigh.  Then  dry  again  for  one  hour,  or  until  there  is  only  a 
slight  change  in  weight. 

NOTE. — In  the  case  of  sweetened  chocolate  and  cocoa  it  is  preferable  to 
use  3-4  grams  for  moisture  and  ash  determination.  f 

Ash  (Official). — Char  the  residue  from  the  moisture  determina- 
tion in  the  platinum  dish  and  burn  until  free  from  carbon  at  not 
exceeding  a  dull  red  heat.  If  impossible  thus  to  burn  the  carbon 
off,  exhaust  the  charred  mass  with  hot  water,  collecting  the  insol- 
uble residue  on  a  filter.  Burn  the  residue  in  the  dish  until  the 
ash  is  white  or  nearly  white,  and  then  add  the  filtrate  to  the  ash 
and  evaporate  to  dryness.  Heat  at  low  redness  until  the  ash  is 
white  or  grayish  white,  cool  and  weigh. 

Ash  Insoluble  in  Acid  (Tentative). — Boil  the  ash  above 
obtained  with  25  cc.  of  10%  HC1  for  five  minutes.  Filter  on  a 
Gooch  crucible  or  ashless  filter.  Wash  with  hot  water,  ignite  and 
weigh. 

Soluble  and  Insoluble  Ash  (Tentative). — Ash  the  material 
as  directed  above,  employing  sufficient  sample  to  contain  approx- 
imately 1  gram  of  water-,  sugar-,  and  fat-free  material.  Add 
water  to  the  ash,  heat  nearly  to  boiling,  filter  through  a  quanti- 
tative paper  and  wash  with  hot  water  until  the  combined  filtrate 
and  washings  measure  about  60  cc.  Return  the  filter  paper  and 
contents  to  the  platinum  dish,  ignite  carefully  and  weigh.  Cal- 
culate percentages  of  water-soluble  and  water-insoluble  ash. 

Alkalinity  of  Soluble  Ash  (Tentative).  —  Cool  the  filtrate 
from  the  above  and  titrate  with  0.1  N  HC1  and  methyl  orange. 
Express  the  alkalinity  in  terms  of  the  number  of  cc.  of  0.1  N  acid 
per  gram  of  sample. 

Alkalinity  of  Insoluble  Ash  (Tentative). — Add  excess  of  0.1  N 
HC1  (usually  10-15  cc.)  to  the  ignited  insoluble  ash  obtained 
above  in  the  platinum  dish.  Heat  to  boiling  over  an  asbestos 
plate,  cool  and  titrate  the  excess  of  HC1  with  0.1  N  NaOH  and 
methyl  orange.  Express  the  alkalinity  in  terms  of  cc.  of  0.1  N 
acid  required  per  gram  of  sample. 

Total  Nitrogen  (Official). — Determine  nitrogen  by  the  Kjeldahl 
or  Gunning  or  Kjeldahl-Gunning- Arnold  method  as  described  on 
page  64. 


432  TECHNICAL   METHODS  OF  ANALYSIS 

Crude  Fiber  (Tentative). — Determine  crude  fiber  according  to 
the  method  on  page  393;  in  cases  of  dispute  use  the  Official 
Method  of  Bulletin  107,  revised  (Bureau  of  Chemistry) . 

For  the  crude  fiber  determination  employ  sufficient  sample  to 
contain  approximately  1  gram  of  water-,  sugar-,  and  fat-free 
material.  Both  filtrations  should  be  made  upon  paper,  the. 
washed  fiber  either  being  weighed  on  a  tared  'filter  in  the  usual 
way  or  rinsed  from  the  paper  into  a  tared  Gooch  crucible,  and 
then  dried  and  weighed. 

NOTE. — The  residue  after  the  fat  extraction  may  be  used  directly  for 
crude  fiber  determination  in  the  analysis  of  commercial  cocoa  and  other  finely 
ground  or  pulverized  cocoa  products.  If,  however,  the  material  is  at  all 
granular,  it  should  be  reduced  to  an  impalpable  powder,  otherwise  results  will 
be  much  too  high.  The  pulverization  may  be  satisfactorily  performed  by 
grinding  with  ether  as  described  later  under  the  determination  of  starch, 
treating  the  extracted  residue  with  hot  H2SO4  (1.25%  solution)  and  proceeding 
from  that  point  in  the  usual  way. 

Crude  Starch,  Direct  Acid  Hydrolysis  (Tentative).* — Weigh 
4  grams  of  sample,  if  unsweetened,  or  10  grams  if  sweetened,  into 
a  small  porcelain  mortar,  add  25  cc.  of  ether  and  grind.  (See 
note.)  After  the  coarser  material  has  settled,  decant  the  ether, 
together  with  fine  suspended  matter,  upon  an  11  cm.  paper  of 
sufficiently  fine  texture  to  retain  crude  starch.  Repeat  this 
treatment  until  no  more  coarse  material  remains.  After  the  ether 
has  evaporated  from  the  filter,  transfer  the  fat-free  residue  to  the 
mortar  by  means  of  a  jet  of  cold  water  and  rub  to  an  even  paste, 
filtering  on  the  paper  previously  employed.  Repeat  the  process 
until  all  sugar  is  removed.  In  case  of  sweetened  products  the 
filtrate  should  measure  at  least  500  cc.  With  unsweetened  mate- 
rial less  washing  is  necessary.  Determine  the  crude  starch  in  the 
extracted  residue  as  follows : 

'  Wash  the  residue  from  the  filter  into  a  500  cc.  Erlenmeyer 
flask  with  200  cc.  of  water.  To  the  solution  so  prepared,  either 
with  sweetened  or  unsweetened  goods,  add  20  cc.  of  dil.  HC1 
(5  :  4)  and  heat  for  2J  hours  in  the  flask  with  a  reflux  condenser. 
Cool  and  nearly  neutralize  with  NaOH.  Add  5  cc.  of  basic  lead 
acetate  solution  and  dilute  to  exactly  250  cc.  Filter,  and  to  100 
cc.  of  the  filtrate  add  1  cc.  of  H2SO4  (60%).  Filter  off  the  PbSO4 
*  The  crude  starch  by  this  method  will  include  pentosans  and  other  carbo- 
hydrate bodies  present  which  are  converted  into  reducing  sugars  by  HC1. 


ANALYSIS  OF  FOODSTUFFS  433 

and  determine  reducing  sugars  in  25  cc.  of  the  filtrate  by  the 
Munson  and  Walker  procedure  as  directed  on  page  403.  The 
weight  of  dextrose  multiplied  by  0.90  gives  the  weight  of  starch. 

NOTE. — If  the  fat  is  to  be  determined,  use  3  grams  of  the  residue  from  the 
fat  extraction  (see  below)  for  the  starch  determination  and  calculate  back 
to  the  original  sample,  correcting  also  for  moisture. 

Pure  Starch,  Diastase  Method  (Tentative). — Remove  fat 
and  sugar  from  4  grams  of  material,  if  unsweetened,  and  10  grams 
if  sweetened,  as  directed  under  Crude  Starch.  Wash  the  wet 
residue  into  a  350  cc.  beaker  with  100  cc.  of  water,  heat  over 
asbestos  to  boiling  with  constant  stirring,  and  continue  boiling 
and  stirring  for  thirty  minutes.  Replace  the  water  lost  by  evap- 
oration and  immerse  the  beaker  in  a  water  bath  kept  between 
55-60°  C.;  cool  to  the  temperature  of  the  bath,  add  20  cc.  of 
freshly  prepared  malt  extract  *  and  digest  the  mixture  for  two 
hours  with  occasional  stirring.  Boil  again  for  thirty  minutes, 
dilute,  cool  and  digest  as  before  with  another  20  cc.  portion  of  malt 
extract.  Heat  again  to  boiling,  cool,  transfer  to  a  250  cc.  flask, 
add  3  cc.  of  alumina  cream,  make  up  to  the  mark  and  filter  through 
dry  paper.  The  residue  on  the  paper  should  show  no  signs  of 
starch  when  treated  with  weak  iodine  solution  and  examined 
microscopically. 

Conduct  the  hydrolysis  of  200  cc.  of  the  filtrate  with  20  cc.  of 
HC1  for  2 . 5  hours  and  determine  the  reducing  power  of  an  aliquot 
of  the  solution  as  directed  under  Crude  Starch.  (Omit  the  addition 
of  the  lead  acetate  and  the  H2SO4.)  Correct  for  the  dextrose 
due  to  added  malt  extract  as  determined  by  an  accompanying 
blank  analysis  upon  20  cc.  of  malt  extract  carried  through  the 
same  procedure. 

Fat  (Tentative). — Dry  2  grams  or  more  of  sample  over  H2S04 
in  a  vacuum  desiccator  until  practically  all  moisture  is  removed. 
(Products  rich  in  fat  show  a  tendency  to  cake  at  the  temperature 
of  boiling  water.  Hence,  drying  by  means  of  heat  must  be 
avoided.)  Extract  with  anhydrous  ether  in  a  continuous  extractor 
until  no  more  fat  is  removed  (generally  eight  to  sixteen  hours). 
Grind  and  repeat  the  extraction  (four  to  eight  hours  is  generally 
enough).  Evaporate  the  ether  and  dry  the  residue  to  constant 
weight  at  100°  C. 

*Malt  Extract.— Digest  10  grams  of  freshly  and  finely  ground  malt  for 
two  or  three  hours  at  room  temperature  with  200  cc.  of  water,  and  filter. 


434  TECHNICAL  METHODS  OF  ANALYSIS 

NOTE. — The  rapid  centrifugal  method,  though  useful  and  accurate  under 
ordinary  conditions,  is  unreliable  during  the  summer  months  or  in  warm 
latitudes  and  has  not  been  approved. 

Sucrose  and  Lactose  (Tentative). — Prepare  the  sample  by 
chilling  well  and  shaving  as  finely  as  possible  with  a  knife.  Trans- 
fer 26  grams  of  this  material  to  an  8-ounce  nursing  bottle,  add  about 
100  cc.  of  petroleum  ether  and  shake  for  five  minutes.  Cen- 
trifugalize  until  the  solvent  is  clear.  Draw  off  by  suction  and 
repeat  the  treatment  with  petroleum  ether.  Place  the  bottle 
containing  the  de-fatted  residue  in  a  warm  place  until  residual 
traces  of  petroleum  ether  are  practically  expelled.  Add  100  cc.  of 
water,  shake  until  all  chocolate  is  loosened  from  the  sides  and 
bottom  of  the  bottle  and  then  shake  three  minutes  longer.  Add 
basic  lead  acetate  solution  from  a  burette  to  complete  precipitation, 
then  sufficient  water  to  make  the  total  volume  of  the  liquid  110  cc. 
Mix  thoroughly  and  filter  through  a  folded  filter.  Make  a  direct 
polariscopic  reading  in  a  200  mm.  tube.  Call  this  A.  Precip- 
itate the  excess  of  Pb  from  solution  with  anhydrous  K2C204,  a 
little  at  a  time,  avoiding  excess.  Filter  out  the  precipitate. 
Introduce  50  cc.  of  lead-free  filtrate  into  a  100  cc.  flask  and  add 
25  cc.  of  water.  Then  add,  little  by  little,  while  rotating  the  flask, 
5  cc.  of  cone.  HC1.  After  mixing,  heat  the  flask  in  a  water  bath 
at  70°  C.  The  temperature  of  the  solution  in  the  flask  should 
read  67-69°  C.  in  two  and  one-half  to  three  minutes.  Maintain 
the  temperature  as  near  69°  C.  as  possible  for  seven  to  seven  and 
one-half  minutes,  making  the  total  time  of  heating  ten  minutes. 
Remove  the  flask  and  cool  the  contents  rapidly  to  20°  C.  and  dilute 
to  100  cc.  Polarize  this  solution  in  a  tube  provided  with  a 
lateral  branch  and  a  water  jacket  maintaining  a  temperature  of 
20°  C.  Multiply  the  invert  reading  by  2  to  correct  for  dilution. 
Call  this  B.  From  the  figures  obtained  calculate  the  percentages 
of  sucrose  (S)  and  lactose  (L)  by  the  following  formulas: 

(A-B)  (110+x) 
S=-  — , 

142M-- 


ANALYSIS  OF  FOODSTUFFS  435 

i 

In  the  first  formula  t  is  the  temperature  at  which  readings  were 
made  and  x  is  obtained  from  the  equation : 

0.2244  (A-2ld) 


1-  0.00204  (A  -21d)' 
and  d  in  this  equation  is  obtained  from 


. 

142.66-^ 

NOTE.  —  Incase  the  determination  of  sucrose  is  not  desired,  the  amount  of 
lactose  may  be  determined  by  the  Defren-O'Sullivan  Method  (see  page  405). 
In  the  case  of  sweetened  products  the  percentage  of  lactose  thus  found  should 
be  corrected  by  subtracting  0.7%  for  invert  sugar  formed  from  the  sucrose. 

Casein  in  Milk  Chocolate  (Tentative).  —  It  is  unnecessary  to 
de-fat  the  chocolate.  Weigh  10  grams  of  sample  into  a  500  cc. 
Erlenmeyer  flask  and  add  exactly  250  cc.  of  1%  Na2C2C>4  solution. 
Heat  to  boiling  and  boil  gently  for  a  few  minutes,  then  cool,  add 
5  grams  of  MgCOs  and  filter.  Determine  nitrogen  in  50  cc.  of 
this  filtrate.  Pipette  100  cc.  of  the  filtrate  into  a  200  cc.  volu- 
metric flask  and  dilute  almost  to  the  mark  with  water.  Then 
precipitate  the  casein  by  addition  of  2  cc.  of  glacial  acetic  acid 
or  1  cc.  of  cone.  H2SO4.  Make  to  volume,  shake,  filter,  and 
determine  nitrogen  in  100  cc.  of  the  filtrate.  The  difference 
between  the  two  nitrogen  determinations  gives  the  nitrogen 
derived  from  the  casein,  which,  multiplied  by  6.38,  gives  the 
amount  of  casein  present  in  2  grams  of  sample  . 

NOTE.  —  Casein  is  approximately  80%  of  the  total  proteins  in  milk;  hence 
to  find  the  total  milk  protein,  divide  by  0.8  the  percentage  of  casein  obtained 
above. 

Theobromine  and  Caffeine.  —  Boil  10  grams  of  the  powdered 
sample  and  5  grams  of  calcined  MgO  for  thirty  minutes  with  300 
cc.  of  water;  filter  by  suction  on  a  Buchner  funnel,  using  a  round 
disk  of  filter  paper.  Transfer  the  material  and  paper  to  the 
original  flask,  add  150  cc.  of  water,  boil  for  fifteen  minutes,  filter 
as  before  and  repeat  the  operation  of  boiling  with  150  cc.  of  water, 


436  TECHNICAL  METHODS  OF  ANALYSIS 

and  filter.  Wash  twice  with  hot  water,  evaporate  the  united 
filtrates  (with  ignited  quartz  sand  if  sugar  be  present)  to  complete 
dryness  in  a  Hoffmeister  Schalchen,  or  other  suitable  thin  glass 
dish  of  about  300  cc.  capacity;  grind  the  dish  with  contents  to  a 
coarse  powder  in  a  mortar;  transfer  to  the  inner  tube  of  a  Weber 
extractor,*  dry  thoroughly  in  a  water  oven  and  extract  with  CHC13 
for  eight  hours  in  a  weighed  flask.  Distill  off  the  CHCls  and  dry 
the  residue  to  constant  weight  at  100°  C.  Treat  the  residue  in 
the  flask  for  some  hours  at  room  temperature  with  50  cc.  of  ben- 
zene. Filter  through  a  small  paper  into  a  tared  dish,  evaporate 
to  dryness  and  dry  to  constant  weight  at  100°  C.,  thus  obtaining 
the  amount  of  caffeine. 

Determine  theobromine  as  follows:  Add  to  the  residue  and 
filter  paper  150  cc.  of  water,  enough  NHUOH  to  make  the  solution 
slightly  alkaline  and  an  excess  of  0.1  N  AgNOs,  accurately  meas- 
ured. Boil  to  half  volume,  add  75  cc.  of  H^O  and  repeat  boiling. 
If  any  NHs  remains,  repeat  the  adding  of  water  and  boiling  until 
the  solution  is  perfectly  neutral.  Filter  off  the  insoluble  silver 
theobromine  compound  and  wash  with  hot  water.  To  the  fil- 
trate and  washings  add  5  cc.  of  a  saturated  solution  of  iron  alum 
and  a  few  cc.  of  HNOs  (free  from  the  lower  oxides  of  N).  Titrate 
the  excess  AgNOs  with  0.1  N  KSCN  until  a  permanent  light  brown 
color  appears.  Subtract  the  amount  of  AgNOs  thus  determined 
from  the  original  amount  added  and  calculate  the  difference  to 
theobromine. 

CALCULATION.— 1  cc.  0.1  N  AgNOs  =  0.01801  gram  theo- 
bromine. 

Other  Nitrogenous  Substances. — Add  the  percentages  of 
nitrogen  present  as  theobromine  and  caffeine,  subtract  the  sum 
from  the  per  cent  of  total  N  and  multiply  the  remainder  by  6.25. 

CALCULATIONS. — Theobromine  X  0.31 1 1  =  Nitrogen. 
Caffeine  X  0.2886          =  Nitrogen. 

Other  Nitrogen  Free-Substances. — To  show  a  complete  anal- 
ysis, subtract  from  100%  the  sum  of  the  percentages  of  moisture, 
ash,  theobromine,  caffeine,  other  nitrogenous  substances,  pure 
starch,  and  fat,  and  report  the  difference  as  "  other  nitrogen-free 
substances." 

*  Any  other  form  of  extractor  which  permits  of  hot  extraction  may  be  used. 


ANALYSIS  OF  FOODSTUFFS  437 

Fat  Constants. — Separate  the  fat  in  a  manner  similar  to  that 
described  above  under  Sucrose  and  Lactose  and  determine  the 
melting  point,  refractive  index  (at  40°  C.),  saponification  number, 
iodine  number  and  Reichert-Meissl  number. 

NOTES. — (1)  Melting  point  determinations  on  this  material  do  not  become 
normal  until  the  fat  has  been  kept  for  at  least  twenty-four  hours  in  a  cool 
place,  preferably  in  a  desiccator. 

(2)  The  constants  for  fat  extracted  from  pure  cocoa  are  as  follows: 

Melting  point 23-28°  C. 

Refractive  index  at  40°  C 1 . 4566-1 . 4579 

Iodine  number 32-41 . 7 

Reichert-Meissl  number 0 . 2-0 . 8 

Saponification  number 192-200 

Milk  Fat  in  Milk  Chocolate. — In  the  case  of  milk  chocolate  the 
.extracted  fat  will  consist  of  cocoa  fat  and  butter.  As  the  Reichert- 
Meissl  number  of  cocoa  fat  is  approximately  0.5  and  that  of  butter 
28.25,  the  approximate  percentage  of  butter  fat  in  the  total  fat 
can  be  calculated  after  determining  its  Reichert-Meissl  number. 

If  A  =  grams  of  butter  fat  in  5  grams  of  mixed  fat, 

B  =  5  —  A  =  grams  of  cocoa  fat  in  5  grams  of  mixed  fat, 
arid     C  =  Reichert-Meissl  number  of  extracted  fat ; 

28.25  A  +0.55     27.75A  +2.5 
then  C=-  -  =  -  — , 


C-0.5 

and  A"5T' 

C— 0  5 

Whence,  per  cent  butter  fat  =  per  cent  total  fat  X—      — . 

27.75 

Milk  Solids  in  Milk  Cocoa  or  Chocolate. — The  milk  solids  are 
calculated  as  the  sum  of  the  butter  fat,  total  milk  proteins,  lac- 
tose, and  milk  ash.  The  amount  of  milk  ash  is  calculated  by 
taking  5%*  of  the  sum  of  the  butter  fat,  milk  proteins,  and 
lactose. 

*  According  to  Leach:  "Food  Inspection    and  Analysis"  this  would  be 
5.9%,  but  the  Food  Laboratories  of  the  U.  S.  Dept  of  Agriculture  use  5%. 


438  TECHNICAL  METHODS  OF  ANALYSIS 

As  a  check  on  the  above  calculations,  it  may  be  noted  that  the 
average  composition  of  milk  solids  is  approximately  as  follows: 

Per  Cent 

Total  protein 29.9 

Lactose 35 . 5 

Butter  fat 28.4 

Ash 5.5 

Citric  acid 0.7 

100.0 
Casein 23 . 7 

REFERENCE. — J.  Assoc.   Official    Agr.     Chemists,   Methods  of  Analysis 
(1916),  page  327;  Leach:   "  Food  Inspection  and  Analysis." 


FEED  STUFFS  AND  MIXED  GRAINS 

Preparation  of  Sample. — Grind  the  sample  so  that  it  will  pass 
through  a  sieve  having  circular  holes  1  mm.  in  diameter.  This  is 
very  important  in  the  case  of  mixed  grains.  A  suitable  mill  is 
the  grinding  and  pulverizing  mill  059  made  by  the  Enterprise 
Mfg.  Co.,  Philadelphia.  The  mill  should  be  screwed  down  tightly 
and  so-called  spice  grinders  used  in  it.  Pass  the  material  through 
the  mill,  sieve  it  on  the  millimeter  sieve,  and  re-grind  the  residue 
until  it  all  passes  the  sieve.  If  it  is  impossible  to  grind  it  fine 
enough  to  go  through  the  sieve,  pound  up  the  residue  in  an  iron 
mortar.  Finally  mix  the  ground  sample  very  thoroughly  before 
removing  portions  for  analysis. 

In  the  case  of  soft  or  sticky  feeds  that  cannot  be  ground,  reduce 
the  sample  to  as  fine  a  state  as  possible. 

NOTE. — For  occasional  samples  the  No.  0  mill  is  satisfactory,  although  this 
is  not  made  to  run  by  power.  The  Bureau  of  Chemistry  at  Washington  uses 
the  Enterprise  Mill,  serial  2962,  which  is  run  by  a  three-quarter  horsepower 
motor. 

1  Moisture. — Dry  a  portion  of  the  ground  material,  representing 
about  2  grams  of  dry  substance,  at  the  temperature  of  boiling 
water  to  constant  weight  (approximately  five  hours)  in  a  current 
of  dry  hydrogen  or  in  vacuo.  If  the  substance  is  in  a  glass  vessel 
the  latter  should  not  be  in  contact  with  the  boiling  water. 


ANALYSIS  OF  FOODSTUFFS  439 

Ash. — Char  about  2  grams  of  the  dry  material  in  a  weighed 
platinum  dish  and  burn  until  free  from  carbonate  at  the  lowest 
possible  heat  (not  above  dull  redness).  If  a  carbon-free  ash  can- 
not be  obtained  in  this  manner,  exhaust  the  charred  mass  with 
hot  water.  Collect  the  insoluble  residue  on  a  filter,  ignite  it  in 
the  dish  until  the  ash  is  white  or  nearly  so,  then  add  the  filtrate 
to  the  ash  in  the  dish  and  evaporate  to  dryness.  Heat  the  whole 
to  low  redness  till  the  ash  is  white  or  grayish  white,  cool  in  a  desic- 
cator and  weigh. 

Crude  Protein. — Determine  the  nitrogen  by  the  Kjeldahl 
method  or  the  Gunning  method  as  described  on  page  64.  Mul- 
tiply the  percentage  of  N  by  6.25  to  obtain  crude  protein. 

Albuminoid  Nitrogen. — (A)  STUTZER'S  REAGENT. — Dissolve 
100  grams  of  pure  copper  sulfate  in  5  liters  of  water,  add  2.5  cc. 
of  glycerol  and  then  dil.  NaOH  solution  until  the  liquid  is  just 
alkaline.  Filter,  rub  the  precipitate  up  with  water  containing 
5  cc.  of  glycerol  per  liter,  and  wash  by  decantation  or  filtration 
until  the  washings  are  no  longer  alkaline.  Rub  the  precipitate 
up  again  in  a  mortar  with  water  containing  10%  of  glycerol, 
thus  preparing  a  uniform  gelatinous  mass  that  can  be  measured 
with  a  pipette.  Determine  the  quantity  of  Cu(OH)2  per  cc.  of 
this  mixture. 

(B)  DETERMINATION. — Place  0.7  gram  of  the  sample  in  a 
beaker,  add  100  cc.  of  water  and  heat  to  boiling;  or,  in  case  of  sub- 
stances rich  in  starch,  heat  on  the  water  bath  for  ten  minutes.  Add 
a  quantity  of  the  Stutzer's  reagent  containing  about  0.5  gram  of  the 
Cu(OH)2,  stir  thoroughly,  filter  when  cold,  wash  with  cold  water 
and,  without  removing  the  precipitate  from  the  filter,  determine 
the  nitrogen  according  to  the  Kjeldahl,  Gunning,  or  Kjeldahl- 
Gunning-Arnold  method,  as  described  on  page  64,  adding  suf- 
ficient K2S  solution  to  completely  precipitate  all  of  the  Cu  and  Hg. 
The  filter  paper  used  must  be  essentially  free  from  N. 

If  the  material  (such  as  seeds,  seed  residue,  or  oil  cake)  is  rich 
in  alkaline  phosphates,  add  1-2  cc.  of  cone,  potash  or  soda  alum 
solution,  free  from  NHs,  then  the  Cu(OH)2  and  mix  well  by 
stirring.  If  this  is  not  done,  copper  phosphate  and  free  alkali 
may  be  formed  and  the  protein-copper  precipitate  partially  dis- 
solved in  the  alkaline  liquid. 


440  TECHNICAL  METHODS  OF  ANALYSIS 

Amido  Nitrogen. — Subtract  the  amount  of  albuminoid  N  from 
the  amount  of  total  N  to  obtain  the  amido  N. 

Crude  Fat  (Ether  Extract). — (A)  REAGENT. — Prepare  anhy- 
drous ether  as  follows:  Wash  the  commercial  ether  with  2-3 
successive  portions  of  water.  Add  solid  NaOH  or  KOH  and  let 
stand  until  most  of  the  water  has  been  extracted.  Decant  into  a 
dry  bottle.  Add  carefully  cleaned  metallic  sodium  cut  into  small 
pieces  and  let  stand  until  there  is  no  further  evolution  of  hydrogen. 
The  ether  thus  dehydrated  must  be  kept  over  metallic  sodium  in  a 
lightly  stoppered  bottle  to  allow  any  accumulated  hydrogen  to 
escape.  It  may  be  drawn  off  with  a  pipette  as  required. 

(B)  DETERMINATION  BY  DIRECT  METHOD. — Large  quantities 
of  soluble  carbohydrates  may  interfere  with  the  complete  extraction 
of  the  fat.      In  such  cases  extract  with  water  before  proceeding 
with  the   determination.     Extract  about  2  grams  of  material, 
dried  as  previously  described,  with  the  anhydrous  ether  for  six- 
teen hours.     Dry  the  extract  at  the  temperature  of  boiling  water 
for  thirty  minutes,  cool  in  a  desiccator  and  weigh.     Continue  the 
alternate  drying  and  weighing  at  thirty-minute  intervals  to  con- 
stant weight.     For  most  feeds  a  period  of  one  to  one  and  one-half 
hours  is  required. 

(C)  INDIRECT  METHOD. — Determine  the  moisture  as  previously 
directed,  then  extract  the  dried  substance  for  sixteen  hours  with 
anhydrous  ether,  dry  again  and  regard  the  loss  in  weight  as  ether 
extract. 

Crude  Fiber. — Determine  the  crude  fiber  as  directed  on  page 
393. 

Carbohydrates. — In  feed  stuffs,  free  from  sugar,  and  in  mixed 
grains  the  carbohydrates  are  generally  taken  by  difference.  Add 
together  the  moisture,  ash,  protein,  fat  and  crude  fiber  and  sub- 
tract the  sum  from  100%  for  the  carbohydrates. 

Total  Sugars.* — (A)  PREPARATION  OF  SOLUTION. — Place  10 
grams  of  the  material  in  a  250  cc.  graduated  flask.  If  the  sub- 
stance has  an  acid  reaction,  add  1-3  grams  of  CaCOs  and  boil  on  a 
steam  bath  for  one  hour  with  150  cc.  of  50%  alcohol  by  volume, 
using  a  small  funnel  in  the  neck  of  the  flask  to  condense  the  vapor. 
Cool  and  let  stand  several  hours,  preferably  overnight.  Make 
up  to  volume  with  neutral  95%  alcohol,  mix  thoroughly,  let 
* -Particularly  applicable  to  cattle  foods. 


ANALYSIS  OF  FOODSTUFFS  441 

settle,  transfer  200  cc.  to  a  beaker  with  a  pipette  and  evaporate 
on  the  steam  bath  to  a  volume  of  20-30  cc.  Do  not  evaporate  to 
dryneas;  a  little  alcohol  in  the  residue  does  no  harm.  Transfer 
to  a  100  cc.  graduated  flask  and  rinse  the  beaker  thoroughly  with 
water,  adding  the  rinsings  to  the  contents  of  the  flask.  Add 
enough  saturated  neutral  lead  acetate  solution  to  produce  a  floc- 
culent  precipitate.  Shake  thoroughly  and  let  stand  fifteen  min- 
utes. Make  up  to  the  mark  with  water,  mix  thoroughly  and 
filter  through  a  dry  filter.  Add  sufficient  anhydrous  Na2COs 
to  the  filtrate  to  precipitate  all  the  Pb.  Again  filter  through 
a  dry  filter  and  test  the  filtrate  with  a  little  anhydrous  Na2COs 
to  make  sure  that  all  the  Pb  has  been  removed. 

(B)  REDUCING   SUGARS. — Determine  the  reducing  sugars  by 
the  Munson  and  Walker  Method  (see  page  403),  employing  the 
Soxhlet  modification  of  Fehling's  solution  and  using  25  cc.  of  the 
solution  prepared  as  above  directed  (representing  2  grams  of  the 
sample).     Express  the  results  as  dextrose  or  invert  sugar.     (See 
note.) 

(C)  SUCROSE. — Introduce  50  cc.  of  the  solution  prepared  as 
above  directed  into  a  100  cc.  graduated  flask;  add  a  piece  of  litmus 
paper,  neutralize  with  acetic  acid,  add  5  cc.  of  cone.  HC1  and  let 
the  inversion  proceed  at  room  temperature  (for  twenty-four  hours 
at  a  temperature  of  20-25°  C.  or  for  ten  hours,  if  the  temperature 
be  above  25°  C.).    When  inversion  is  complete,  transfer  the  solu- 
tion to  a  beaker.     Neutralize  with  Na2COs,  return  the  solution  to 
the  100  cc.  flask,  dilute  to  the  mark  with  water,  filter  if  necessary 
and  determine  reducing  sugars  in  50  cc.  of  the  solution  (represent- 
ing 2  grams  of  the  sample),  as  directed  under  Reducing  Sugars 
above,  and  calculate  the  result  as  invert  sugar.     Subtract  the  per 
cent  of  reducing  sugars  before  inversion  from  the  per  cent  of  total 
sugar    after    inversion,   both   calculated    as    invert    sugar,    and 
multiply  the  difference  by  0.95  to  obtain  the  per  cent  of  sucrose 
present. 

NOTE — Since  the  insoluble  material  of  grain  or  cattle  food  occupies 
some  space  in  the  flask  as  originally  made  up,  it  is  necessary  to  correct  for  this 
volume.  Results  of  a  large  number  of  determinations  on  various  materials 
have  shown  the  average  volume  of  10  grams  of  material  to  be  7.5  cc.  and 
therefore  to  obtain  the  true  amount  of  sugars  present  all  results  must  be 
multiplied  by  the  factor  0.97  (since  7.5  cc.  is  3%  of  250  cc.). 


442  TECHNICAL  METHODS  OF  ANALYSIS 

Starch  (Direct  Acid  Hydrolysis,  Modified  Sachsse  Method.)— 
By  this  method  there  will  be  included  as  starch  the  pentosans 
and  other  carbohydrate  bodies  present  which  undergo  hydrolysis 
and  inversion  to  reducing  sugars  on  boiling  with  HC1. 

PROCEDURE. — Stir  a  quantity  of  the  sample  representing  2.5-3 
grams  of  the  dry  material  in  a  beaker  with  50  cc.  of  cold  water 
for  one  hour.  Transfer  to  a  filter  and  wash  with  250  cc.  of  cold 
water.  Heat  the  insoluble  residue  for  two  and  one-half  hours 
with  200  cc.  of  water  and  20  cc.  of  dil.  HC1  (5  :  4)  in  a  flask  pro- 
vided with  a  reflux  condenser.  Cool  and  nearly  neutralize  with 
NaOH.  Add  the  proper  clarifying  agent  and  complete  the  volume 
to  250  cc.  Filter  and  determine  the  dextrose  in  an  aliquot  of  the 
filtrate  as  directed  by  the  Munson  and  Walker  Method  (page  403), 
or  the  Allihn  Method  (page  407). 

The  weight  of  dextrose  obtained,  multiplied  by  0.90,  gives  the 
weight  of  starch. 

NOTE. — The  factor  0.90  is  the  theoretical  ratio  between  starch  and  glucose, 
but,  according  to  Noyes  and  other  investigators,  the  factor  0.93  more  nearly 
approaches  the  actual  yield. 

Pentosans. — The  determination  of  pentosans  is  seldom  neces- 
sary. No  official  method  has  yet  been  adopted.  The  tentative 
method  of  the  Association  of  Official  Agricultural  Chemists  is 
described  under  Furfural  Value  of  Cotton  Cellulose  on  page  366. 

Galactan. — The  same  remarks  apply  to  galactan  as  to  pen- 
tosans. The  tentative  method  is  described  in  J.  Assoc.  Official 
Agr.  Chemists,  Methods  of  Analysis  (1916),  page  118. 

Water-soluble  Acidity  (Tentative). — Weigh  10  grams  of  the 
sample  into  a  shaking  bottle.  Add  200  cc.  of  water  and  shake  for 
fifteen  minutes.  Filter  the  extract  through  a  folded  filter,  pipette 
out  200  cc.  (equivalent  to  1  gram),  dilute  with  50  cc.  of  water  and 
titrate  with  0.1  N  NaOH  and  phenolphthalein.  State  the  result 
in  terms  of  cc.  of  0.1  N  NaOH  required  for  neutralization. 

REFERENCE. — The  above  are  essentially  the  official  methods  of  the  Assoc. 
Official  Agr.  Chemists  (except  those  marked  Tentative)  described  in  its  Jour- 
nal, Methods  of  Analysis  (1916),  pages  79-120.  There  have  been,  slight 
changes* made  to  conform  to  the  usage  of  this  laboratory. 


ANALYSIS  OF  FOODSTUFFS  443 

MILK  AND  CREAM 
MILK 

General. — The  sp.  gr.  of  pure  milk  at  60°  F.  generally  ranges 
from  1.027-1.035.  Its  average  composition  is  approximately  as 

follows : 

Per  Cent 

Butter  Fat 3.6 

Solids  not  Fat: 

Casein 3.0 

Other  nitrogenous  sub- 
stances  0.8  \         9.1 

Lactose 4.5 

Citric  Acid 0.1 

Ash 0.7 

Total  Solids 12.7 

According  to  the  above  figures,  the  composition  of  the  solids 

should  be  as  follows: 

Per  Cent 

Casein 23.7 

Lactose 35 . 5 

Fat 28.4 

Ash 5.5 

Total  Protein 29.9 

It  will  be  seen  that  casein  is  about  80  per  cent  of  the  total  protein. 
The  U.  S.  federal  standard  for  pure  milk  (Bureau  of  Chem., 

Circular  19)  is  as  follows: 

Per  Cent 

Solids  not  Fat minimum  8 . 5 

Milk  Fat minimum  3 . 25 

Skimmed  milk  should  contain  not  less  than  9.25%  of  milk 
solids. 

The  usual  determinations  in  ascertaining  the  nutritive  values 
of  milk  are  Specific  Gravity,  Total  Solids,  Fat,  Protein,  Lactose, 
and  Ash.  The  following  methods,  unless  otherwise  indicated, 
are  the  official  methods  of  the  Association  of  Official  Agricultural 
Chemists. 


444  TECHNICAL  METHODS  OF  ANALYSIS 

Specific  Gravity.* — Determine  the  sp.  gr.  at  60°  F.  with  a 
pycnometer,  first  shaking  the  sample  well. 

Total  Solids. — Heat  3-5  grams  of  the  milk  at  the  temperature 
of  boiling  water  until  it  ceases  to  lose  weight,  using  a  tared,  flat- 
bottomed  dish  of  not  less  than  5  cm.  diameter.  If  desired,  previ- 
ously place  15-20  grams  of  pure,  dry  sand  in  the  dish.  Cool  in 
a  desiccator  and  weigh  rapidly  to  avoid  absorption  of  hygro- 
scopic moisture. 

Ash. — Weigh  about  20  grams  of  the  milk  in  a  tared  porcelain 
dish,  add  6  cc.  of  HNOs,  evaporate  to  dryness  and  ignite  at  a 
temperature  just  below  redness  until  the  ash  is  free  from  carbon. 

Protein. — Place  about  5  grams  of  the  milk  in  a  Kjeldahl  diges- 
tion flask  and  determine  (without  evaporation)  the  total  N  by 
the  Kjeldahl  or  Gunning  or  the  Kjeldahl-Gunning- Arnold  method 
(page  64).  Multiply  the  percentage  of  N  by  6.38  to  obtain  the 
percentage  of  N  compounds  or  total  protein. 

Casein. — This  determination  should  be  made  while  the  milk 
is  fresh  or  nearly  so.  If  it  cannot  be  made  within  24  hours,  add 
1  part  of  formaldehyde  to  2500  parts  of  the  milk  and  keep  in  a 
cool  place. 

METHOD  No.  1. — Place  10  grams  of  the  milk  in  a  beaker 
'with  90  cc.  of  water  at  40-42°  C.  and  add  at  once  1.5  cc.  of  10% 
acetic  acid.  Stir  and  let  stand  3-5  minutes.  Then  decant  and 
filter,  wash  by  decantation  2-3  times  with  cold  water  and  trans- 
fer the  precipitate  to  the  filter.  Wash  once  or  twice  on  the  filter. 
The  filtrate  should  be  clear,  or  very  nearly  so.  If  the  first  por- 
tions of  the  filtrate  are  not  clear,  repeat  the  filtration,  after  which 
complete  the  washing  of  the  precipitate.  Determine  N  in  the 
washed  precipitate  and  filter  paper  as  directed  above,  multiply 
by  6.38  and  calculate  the  percentage  of  casein. 

In  samples  of  milk  which  have  been  preserved,  the  acetic  acid 
should  be  added  in  small  portions,  a  few  drops  at  a  time,  with 
stirring,  and  the  addition  continued  until  the  liquid  above  the 
precipitate  becomes  clear,  or  very  nearly  so. 

METHOD  No.  2. — To  10  grams  of  the  milk  add  50  cc.  of  water 

at  40°  C.,  then  2  cc.  of  alum  solution,  saturated  at  40°  C.  or 

higher.     Let  the  precipitate  settle,  transfer  to  a  filter  and  wash 

with  cold  water.     Determine  N  in  the  precipitate  and  filter  paper 

*  Not  included  in  the  A.  0.  A.  C,  method. 


ANALYSIS  OF  FOODSTUFFS  445 

as  directed  above,  multiply  by  6.38  and  calculate  the  percentage  of 
casein. 

Lactose. — Dilute  25  grams  of  the  milk  with  400  cc.  of  water 
in  a  500  cc.  volumetric  flask.  Add  10  cc.  of  Fehling's  copper 
sulfate  solution  (Soxhlet  modification)  and  about  7.5  cc.  of  KOH 
solution  of  such  strength  that  1  volume  is  just  sufficient  to  pre- 
cipitate completely  the  Cu  from  1  volume  of  the  Fehling's  solu- 
tion. (Instead  of  KOH  of  this  strength,  8.8  cc.  of  0.5  N  NaOH 
solution  may  be  used.)  After  the  addition  of  the  alkali  solution, 
the  mixture  must  still  have  an  acid  reaction  and  contain  copper 
in  solution. 

Dilute  the  solution  to  the  mark,  mix,  filter  through  a  dry 
filter  and  determine  lactose  in  an  aliquot  of  the  filtrate  by  the 
Munson  and  Walker  method  (page  403). 

Fat  (Roese-Gottlieb  Method).— Weigh  10-11  grams  of  the 
milk  into  a  Rohrig  tube  or  some  similar  apparatus,  add  1.25  cc. 
of  cone.  NELtOH  (2  cc.  if  the  sample  is  sour)  and  mix  thoroughly. 
Add  10  cc.  of  95%  alcohol  by  volume  and  mix  well.  Then  add 
25  cc.  of  washed  ether  and  shake  vigorously  for  30  seconds,  then 
25  cc.  of  petroleum  ether  (re-distilled  slowly  at  a  temperature  below 
60°  C.)  and  shake  again  for  30  seconds.  Let  stand  20  minutes, 
or  until  the  upper  liquid  is  practically  clear.  Draw  off  as  much 
as  possible  of  the  ether-fat  solution  (usually  0.5-0.8  cc.  will  be 
left)  into  a  weighed  flask  through  a  small,  quick-acting  filter. 
(The  flask  should  always  be  weighed  with  a  similar  one  as  a  counter- 
poise.) Re-extract  the  liquid  remaining  in  the  tube,  this  time 
with  only  15  cc.  of  each  ether,  shake  vigorously  30  seconds  with 
each  and  let  settle.  Draw  off  the  clear  solution  through  the 
small  filter  into  the  same  flask  as  before  and  wash  the  tip  of  the 
spigot,  the  funnel  and  the  filter  with  a  few  cc.  of  a  mixture  of  the 
two  ethers  in  equal  parts.  For  absolutely  exact  results  the 
re-extraction  must  be  repeated.  This  third  extraction  yields 
usually  not  more  than  about  1  mg.  of  fat  (about  0.02%  on  a  4-gram 
charge)  if  the  previous  ether-fat  solutions  have  been  drawn  off 
closely.  Evaporate  the  ethers  slowly  on  the  steam  bath,  then 
dry  the  fat  in  a  boiling  water  oven  to  constant  weight. 

Confirm  the  purity  of  the  fat  by  dissolving  in  a  little  petroleum 
ether.  Should  a  resin  remain,  remove*  the  fat  completely  with 
petroleum  ether,  dry  the  residue,  weigh  and  deduct  the  weight. 


446  TECHNICAL  METHODS  OF  ANALYSIS 

Finally  correct  this  weight  by  a  blank    determination    on  the 
reagents  used. 

Fat  (Babcock  Method).— (I)  APPARATUS. 

(a)  Standard  Babcock  test  bottles. — The  standard  Babcock 
test  bottles  for  milk  and  cream  shall  be  as  follows : 

(1)  8%,  18  GRAM,  6-lNCH   MILK  TEST  BOTTLE.— The 

total  per  cent  graduation  shall  be  8.  The  total 
height  of  the  bottle  shall  be  150-165  mm.  (5|- 
6i  inches) .  The  capacity  of  the  bulb  up  to  the 
junction  with  the  neck  shall  be  not  less  than 
45  cc.  The  graduated  portion  of  the  neck 
shall  have  a  length  of  not  less  than  63.5  mm. 
(2.5  inches)  and  the  neck  shall  be  cylindrical 
for  at  least  9  mm.  below  the  lowest  and  above 
the  highest  graduation  marks.  The  gradu- 
ations shall  represent  whole  per  cents,  halves 
and  tenths  of  a  per  cent. 

(2)  50%,  9  GRAM,   6-lNCH  CREAM   TEST  BOTTLE.— 

The  total  per  cent  graduation  shall  be  50.  The 
total  height  of  the  bottle  shall  be  150-165  mm. 
(5|-6|  inches).  The  capacity  of  the  bulb  up 
to  the  junction  with  the  neck  shall  be  not  less 
than  45  cc.  The  graduated  portion  of  the  neck 
shall  have  a  length  of  not  less  than  63.5  mm. 
(2.5  inches)  and  the  neck  shall  be  cylindrical 
for  at  least  9  mm.  below  the  lowest  and  above 
the  highest  graduation  marks.  The  graduations 
shall  represent  five  per  cents,  whole  and  halves 
of  a  per  cent. 

(3)  50%,   9  GRAM,  9-lNCH  CREAM  TEST  BOTTLE.— 

Same  as  (2)  except  that  the  total  height  of  the 
bottle  shall  be  210-225  mm.     (8J-8f  inches.) 
(6)  Centrifuge. 

(c)  Pipettes. — Graduated  to  deliver  17.6  cc.  of  water  at 

20°  C.  in  5-8  seconds. 

(d)  Graduates. — Capacity  17.5  cc.  or  a  Swedish  acid  bottle 

delivering  that  amount. 
(II)  CALIBRATION  OF  APPARATUS. 

(a)  Graduation. — The  unit  of  graduation  for  all  Babcock 


ANALYSIS  OF  FOODSTUFFS  447 

glassware  shall  be  the  true  cc.  (0.998877  gram  of 
water  at  4°  C.).  With  bottles,  the  capacity  of  each 
per  cent  on  the  scale  shall  be  0.20  cc.  With  pipettes 
and  graduates,  the  delivery  shall  be  the  intent  of 
the  graduation;  and  the  graduation  shall  be  read 
with  the  bottom  of  the  meniscus  in  line  with  the 
mark. 

(6)  Testing. — The  method  for  testing  Babcock  bottles 
shall  be  calibration  with  mercury  (13.5471  grams  of 
clean,  dry  mercury  at  20°  C.,  to  be  equal  to  5%  on 
the  scale),  the  bottle  being  previously  filled  to  zero 
with  mercury.  (The  mercury  and  cork,  alcohol  and 
burette,  and  alcohol  and  brass  plunger  methods  may 
be  employed  for  the  rapid  testing  of  Babcock  bottles, 
but  the  accuracy  of  all  questionable  bottles  shall  be 
determined  by  calibration  with  mercury.) 
The  method  for  testing  pipettes  and  graduates  shall  be 
calibration  by  measuring  in  a  burette  the  quantity 
of  water  (at  20°  C.)  delivered. 

(c)  Limit  of  error. — For  standard  Babcock  milk  bottles  the 
error  at  any  point  of  the  scale  shall  not  exceed 
0.1%.  For  standard  Babcock  cream  bottles  the 
error  at  any  point  of  the  scale  shall  not  exceed  0.5%. 
For  standard  milk  pipettes  the  error  shall  not  exceed 
0.05  cc.  For  acid  measures  the  error  shall  not 
exceed  0.2  cc. 
(Ill)  DETERMINATION. 

Pipette  17.6  cc.  of  the  carefully  mixed  sample  into  a  test 
bottle  and  add  17.5  cc.  of  commercial  H2SO4  (sp. 
gr.  1.82-1.83).  Mix  and,  when  the  curd  is  dis- 
solved, centrifugalize  for  4  minutes  at  the  required 
speed  for  the  machine  used.  Add  boiling  water, 
filling  to  the  neck  of  the  bottle,  and  whirl  for  1 
minute;  again  add  boiling  water  so  as  to  bring  the 
fat  within  the  scale  on  the  neck  of  the  bottle,  and, 
after  whirling  for  1  minute  more,  read  the  length 
of  the  fat  column,  making  the  reading  57-60°  C., 
at  which  temperature  the  fat  is  wholly  liquid.  The 
reading  gives  directly  the  per  cent  of  fat  in  the  milk. 


448  TECHNICAL  METHODS  OF  ANALYSIS 

Gelatin  (Qualitative  Test— Tentative).— To  10  cc.  of  the  milk 
add  an  equal  volume  of  acid  Hg(NOa)2  solution  (Hg  dissolved  in 
twice  its  weight  of  cone.  HNOs  and  this  solution  diluted  to  25 
times  its  volume  with  water),  shake  the  mixture,  add  20  cc.  of 
water,  shake  again,  let  stand  5  minutes  and  filter.  If  much  gel- 
atin is  present,  the  nitrate  will  be  opalescent  and  cannot  be  obtained 
quite  clear.  To  a  portion  of  the  filtrate  contained  in  a  test-tube, 
add  an  equal  volume  of  saturated  aqueous  picric  acid  solution. 
A  yellow  precipitate  will  be  produced  in  the  presence  of  any  con- 
siderable amount  of  gelatin,  while  smaller  amounts  will  be  indi- 
cated by  a  cloudiness.  In  the  absence  of  gelatin  the  filtrate  will 
remain  perfectly  clear. 

Preservatives. — For  these  tests  see  J.  Assoc.  Off.  Agr.  Chem. 
Methods  of  Analysis,  1916,  page  141.  To  test  for  salicylic  or 
benzoic  acid,  first  acidify  100  cc.  of  the  milk  with  5  cc.  of  HC1 
(1  :  3),  shake  until  curdled,  filter  and  proceed  with  the  clear  filtrate. 

Coloring  Matter  (Leach  Method — Tentative). — Warm  about 
150  cc.  of  milk  in  a  casserole  over  a  flame  and  add  about  5  cc.  of 
acetic  acid,  then  slowly  continue  the  heating  nearly  to  the  boiling 
point  while  stirring.  Gather  the  curd,  when  possible,  into  one 
mass  with  a  stirring  rod  and  pour  off  the  whey.  If  the  curd  breaks 
up  into  small  flecks,  separate  from  the  whey  by  straining  through 
a  sieve  or  colander.  Press  the  curd  free  from  adhering  liquid, 
transfer  to  a  small  flask  and  macerate  for  several  hours,  prefer- 
ably overnight,  in  about  50  cc.  of  ether,  the  flask  being  tightly 
corked  and  shaken  at  intervals.  Decant  the  ether  extract  into 
an  evaporating  dish,  remove  the  ether  by  evaporation  and  test 
the  fatty  residue  for  annatto  as  directed  on  page  392. 

The  curd  of  an  uncolored  milk  is  perfectly  white  after  complete 
extraction  with  ether,  as  is  also  that  of  a  milk  colored  with  annatto. 
If  the  extracted  fat-free  curd  is  distinctly  colored  an  orange  or 
yellowish  color,  a  coal  tar  dye  is  indicated.  In  many  cases,  upon 
treating  a  lump  of  a  fat-free  curd  in  a  test-tube  with  a  little  strong 
HC1  the  color  changes  to  pink,  indicating  the  presence  of  a  dye 
similar  to  aniline  yellow  or  butter  yellow  or  perhaps  one  of  the 
acid  azo  yellows  or  oranges.  In  such  cases,  separate  and  identify 
the  coloring  matter  present  in  the  curd  as  directed  on  page  389. 
If  aniline  yellow,  butter  yellow,  or  other  oil-soluble  dye  is  present, 
the  greater  part  will  be  found  in  the  ether  extract  containing  the 


ANALYSIS  OF  FOODSTUFFS  449 

fat.     In  such  cases  proceed  as  directed  on  page  391  under  Oil- 
soluble  Dyes. 

In  some  cases  the  presence  of  coal  tar  dyes  can  be  detected  by 
treating  about  10  cc.  of  the  milk  directly  with  an  equal  volume 
of  cone.  HC1  in  a  procelain  casserole,  giving  the  dish  a  slight  rotary 
motion.  In  the  presence  of  some  dyes  the  separated  curd  acquires 
a  pink  coloration. 

CREAM 

Total  Solids. — Follow  the  same  procedure  as  for  Milk,  using 
2-3  grams  of  the  sample. 

Ash,  Protein,  and  Lactose. — Proceed  as  above  under  Milk. 

Fat. — Follow  the  method  given  above  under  Milk.  For  the 
extraction  method,  weigh  4-5  grams  of  the  homogeneous  sample 
into  a  Rohrig  tube  or  similar  apparatus,  dilute  with  water  to  about 
10.5  cc.  and  proceed  as  directed. 

For  the  Babcock  method,  weigh  9  or  18  grams,  depending 
upon  the  fat  content,  into  a  standard  Babcock  cream  bottle  and 
proceed  as  directed. 

Gelatin. — Follow  the  same  procedure  as  for  Milk. 

Coloring  Matter. — Follow  the  procedure  on  page  389,  par- 
ticularly looking  for  oil-soluble  dyes  and  annatto. 

Preservatives.^-Proceed  as  directed  on  page  448. 

REFERENCE. — J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis  (1916- 
17),  pages  287-293. 

CONDENSED  OR  EVAPORATED  MILK 

General. — The  common  meaning  of  "  condensed  milk  "  in 
this  country  is  milk  which  has  been  condensed  and  preserved 
with  cane  sugar.  Milk  which  has  been  condensed  without  added 
sweetening  is  often  termed  "  evaporated  cream,"  although  this 
term  is  a  misnomer. 

The  U.  S.  Standard  for  condensed  milk  requires  not  less  than 
25.5%  of  milk  solids  and  not  less  than  7.8%  of  milk  fat  (Food 
Inspection  Decision  158). 

In  the  case  of  unsweetened  condensed  milk,  dilute  40  grams 
of  the  homogeneous  sample  with  60  grams  of  water  and  make  the 


450  TECHNICAL  METHODS  OF  ANALYSIS 

determinations  as  directed  under  Milk  and  Cream,  (page  443) 
correcting  the  results  for  the  dilution. 

The  following  procedures  are  to  be  used  on  sweetened  products. 

Preparation  of  Sample.— Warm  the  sample  to  30-35°  C., 
transfer  to  a  dish  sufficiently  large  to  stir  thoroughly  and  make 
the  whole  mass  homogeneous.  Weigh  100  grams  into  a  500  cc. 
volumetric  flask  and  dilute  to  the  mark  with  water.  If  the  milk 
will  not  dissolve,  weigh  out  each  portion  for  analysis  separately. 

Total  Solids  and  Moisture. — Pipette  10  cc.  of  the  above  solu- 
tion into  a  small  weighed  platinum  dish  containing  15-20  grams 
of  pure,  dry  sand  or  asbestos  fiber,  which  has  previously  been 
ignited  and  weighed  with  the  dish.  Dry  to  constant  weight  at 
the  temperature  of  boiling  water,  cool  in  a  desiccator  and  weigh 
rapidly.  Consider  the  difference  between  the  percentage  of  total 
solids  and  100%  to  be  moisture. 

Ash. — Ignite  the  residue  from  the  total  solids  carefully,  cool 
and  weigh. 

Protein. — Pipette  10  cc.  of  the  prepared  solution  into  a  Kjeldahl 
flask  and  determine  nitrogen  (without  evaporation)  by  the  Kjel- 
dahl or  Gunning  or  Kjeldahl-Gunning- Arnold  method  as  described 
on  page  64.  Multiply  the  N  by  6.38  to  obtain  the  protein. 

Lactose  (Milk  Sugar). — Dilute  100  cc.  of  the  prepared  solu- 
tion in  a  250  cc.  volumetric  flask  to  about  200  cc.  Add  6  cc.  of 
Fehling's  copper  sulfate  solution  (Soxhlet  modification)  and  dilute 
to  the  mark.  Filter  through  a  dry  filter  and  determine  lactose 
by  the  Munson  and  Walker  Method  (page  403). 

Fat. — (1)  RESE-GOTTLIEB  METHOD. — Weigh  4-5  grams  of 
the  original  homogeneous  sample  into  a  Rohrig  tube  or  similar 
apparatus,  dilute  with  water  to  about  10.5  cc.  and  proceed  as 
directed  under  Milk  and  Cream  (page  445). 

(2)  ADAMS  METHOD. — Prepare  strips  of  soft  white  filter 
paper  about  4X12  inches,  of  the  quality  of  S.  and  S.  No.  597,  by 
soaking  2  or  3  hours  in  alcohol  and  then,  after  thoroughly  drying 
in  the  oven,  extract  several  hours  with  ether  or  until  no  residue 
is  left  from  the  ether  as  it  comes  through.  Distribute  5  cc.  of 
a  40%  solution  of  the  condensed  milk  carefully  over  the  whole 
surface  of  the  thoroughly  dried  paper.  (This  is  best  done  by 
attaching  one  end  of  the  paper  to  some  object  and  holding  the 
other  end  out  straight  so  that  the  pipette  can  be  emptied  by  pass- 


ANALYSIS  OF  FOODSTUFFS  451 

ing  the  point  back  and  forth  over  the  whole  surface.)  To  dry  the 
paper,  suspend  it  over  a  copper  wire  in  the  drying  oven,  where 
it  will  thoroughly  dry  out  in  2  hours,  or  much  more  rapidly  than 
if  coiled  up  or  put  in  a  tube.  After  drying,  roll  up  in  a  coil,  wind 
with  thread  or  small  copper  wire,  place  in  the  Soxhlet  extractor, 
and  extract  with  ether  for  not  less  than  8  hours.  .Remove  the 
coil  from  the  extractor,  loosen  the  wire  or  thread  and  let  the  ether 
evaporate.  Suspend  in  500  cc.  of  water  for  2  hours,  then  return 
the  coil  to  the  oven,  dry  as  before,  and  extract  again  for  not  less 
than  5  hours. 

Sucrose. — Determine  sucrose  "  by  difference,"  deducting  from 
100%  the  sum  of  the  moisture,  ash,  protein,  lactose  and  fat. 

Milk  Solids. — These  are  the  total  solids,  minus  the  sucrose. 

REFERENCES. — The  above  are  the  official  methods  of  the  Association  of 
Official  Agr.  Chem.  as  published  in  its  Journal,  II,  Methods  of  Analysis 
(1916-17),  page  293,  except  the  Adams  Method  for  Fat,  which  is  described  in 
Leach:  "  Food  Inspection  and  Analysis  "  (1914  ed.),  page  154. 

CHEESE 

General. — The  U.  S.  Government  standard  for  cheese  accord- 
ing to  Circular  No.  19  is  as  follows:  Cheese  is  made  from  milk 
or  cream  by  coagulating  the  casein  with  rennet  or  lactic  acid, 
with  or  without  the  addition  of  ripening  ferments  and  seasoning, 
and  contains  in  the  water-free  substance  not  less  than  50%  of 
milk  fat.  It  may  also  contain  added  coloring  matter. 

Cheese  is  sometimes  adulterated  by  preserving  with  boric 
acid  or  borax.  (See  page  284  for  detection.) 

The  following  procedures,  unless  otherwise  indicated,  are 
the  official  methods  of  the  Association  of  Official  Agricultural 
Chemists. 

Sampling. — When  the  cheese  can  be  cut,  take  a  narrow  wedge- 
shaped  segment  reaching  from  the  outer  edge  to  the  center.  Cut 
into  strips  and  pass  three  times  through  a  sausage  machine. 
When  the  cheese  cannot  be  cut,  take  the  sample  with  a  cheese 
trier.  If  only  one  plug  can  be  obtained,  take  it  perpendicular  to 
the  surface  of  the  cheese  at  a  point  one-third  the  distance  from  the 
edge  to  the  center,  extending  either  entirely  or  half-way  through. 
When  possible,  draw  3  plugs:  1  from  the  center,  1  from  a  point 


452  TECHNICAL  METHODS  OF  ANALYSIS 

near  the  outer  edge,  and  1  from  a  point  half-way  between  the 
other  two.  For  inspection  purposes  reject  the  rind,  but  for  inves- 
tigations requiring  the  absolute  amount  of  fat  in  cheese  include 
the  rind  in  the  sample.  Either  grind  the  plugs  in  a  sausage  machine 
or  cut  very  finely  and  mix  carefully,  preferably  the  former. 

Moisture  (Tentative). — Place  2-3  grams  of  very  short  fiber 
asbestos  (long  fiber  may  be  made  suitable  by  rubbing  through  a 
fine  sieve)  in  a  flat-bottomed  platinum  dish,  6-7  cm.  in  diameter, 
and  pres's  the  asbestos  down  firmly.  Place  in  the  dish  a  glass  rod 
about  5  mm.  in  diameter  and  slightly  longer  than  the  diameter  of 
the  dish.  Ignite,  cool  and  weigh  the  dish  and  contents.  Then 
weigh  into  the  dish  4-5  grams  of  sample,  prepared  as  above,  and 
mix  the  cheese  and  asbestos  intimately  with  the  glass  rod  until 
the  mass  is  homogeneous.  Leave  the  mass  in  as  loose  a  condi- 
tion as  possible  to  facilitate  drying.  Dry  the  mixture  in  an  oven 
at  100°  C.  and  weigh  at  intervals  of  one  to  one  and  one-half  hours 
until  the  weight  becomes  constant.  (Three  weighings  are  usually 
sufficient.) 

Ash. — Ignite  the  residue  from  the  moisture  determination 
cautiously  to  avoid  spattering  and  remove  the  heat  while  the  fat 
is  burning  off.  When  the  flame  has  died  out,  complete  the  burning 
in  a  muffle  at  low  redness.  Cool  in  a  desiccator  and  weigh  the 
ash. 

Salt. — Dissolve  the  ash  from  the  above  determination  in  water 
slightly  acidified  with  HNOs,  and  determine  the  chlorine,  either 
gravimetrically  as  AgClj  or  volumetrically  by  the  chromate  method 
as  on  page  492.  Calculate  to  NaCl. 

CALCULATION.— AgCl  X  0.4078         =  NaCl. 

1  cc.  0.1  N  AgNO3  =  0.005846  gram  NaCl. 

Nitrogen. — Determine  nitrogen  by  the  Kjeldahl  or  Gunning  or 
Kjeldahl-Gunning- Arnold  method  as  on  page  64,  using  about  2 
grams  of  cheese,  and  multiply  the  per  cent  of  N  by  6.38  to  obtain 
the  per  cent  of  nitrogen  compounds. 

Acidity  (Tentative). — To  10  grams  of  finely  divided  cheese 
add  water  at  40°  C.  until  the  volume  equals  105  cc.  Shake  vigor- 
ously and  filter.  Titrate  25  cc.  portions  of  the  filtrate,  representing 
2.5  grams  of  sample,  with  0.1  N  NaOH  and  phenolphthalein. 
Express  results  in  terms  of  lactic  acid. 

CALCULATION. — 1  cc.  0.1  N  NaOH  =  0.009  gram  lactic  acid. 


ANALYSIS  OF  FOODSTUFFS  453 

Coloring  Matters  (Tentative). — Proceed  according  to  page  389. 

Fat.  (A)  PREPARATION  OF  SAMPLE  (TENTATIVE). —  (1)  Alka- 
line extraction. — Treat  about  300  grams  of  cheese,  cut  into  frag- 
ments the  size  of  a  pea,  with  700  cc.  of  5%  KOH  solution  at  20°  C. 
in  alarge,  wide-necked  flask.  Shake  vigorously  to  dissolve  the 
casein.  In  five  to  ten  minutes  the  casein  will  be  dissolved  and  the 
fat  will  rise  to  the  surface  in  lumps.  Collect  into  as  large  a  mass  as 
possible  by  shaking  gently.  Pour  cold  water  into  the  flask  until  the 
fat  is  driven  up  into  the  neck  and  remove  with  a  pipette.  Wash 
the  fat  thus  obtained  with  just  sufficient  water  to  remove  any 
alkali.  The  fat  is  not  perceptibly  attacked  by  the  alkali  in  this 
treatment  and  is  practically  all  separated  in  a  short  time.  It  is 
then  prepared  for  chemical  analysis  by  filtering  through  a  dry 
filter  paper  in  a  hot  water  funnel  at  about  60°  C.  Refilter,  if 
necessary,  and  dry. 

(2)  Acid  extraction — Pass  the  cheese  through  a  grinding 
machine;  transfer  to  a  large  flask  and  cover  with  warm  water, 
using  1  cc.  for  every  gram  of  cheese.  Shake  thoroughly  and  add 
H2SO4  (sp.  gr.  1.82-1.825)  slowly  and  in  small  quantities,  shaking 
after  each  addition.  The  total  amount  of  acid  used  should  be  the 
same  as  the  amount  of  water.  Remove  the  fat,  which  separates 
after  standing  a  few  minutes,  by  means  of  a  separatory  funnel, 
wash  free  from  acid,  filter  and  dry  as  above. 

(B)  EXAMINATION  OF  FAT. — Make  such  tests  as  are  necessary 
on  the  fat  by  procedures  described  on  pages  230,  241,   and  243. 
As  a  general  rule  the  sp.    gr.,   refractive  index,  iodine  number, 
and  Reichert-Meissl  number  will  be  sufficient. 

(C)  QUANTITATIVE   ESTIMATION. — Cover   the  perforations  on 
the  bottom  of  an  extraction  tube  with  dry  asbestos  and  place  on 
this  a  mixture  containing  equal  parts  of  anhydrous  CuSCU  and 
pure  dry  sand  to  a  depth  of  about  5  cm.,  packing  loosely.  Cover  the 
upper  surface  of  this  mixture  with  a  layer  of  asbestos.     Place  on 
this  2-5  grams  of  the  sample  and  extract  with  anhydrous  ether 
for  five  hours  in  a  continuous  extraction  apparatus.     Remove  the 
cheese  and  grind  it  with  pure  sand  in  a  mortar  to  a  fine  powder. 
Return  the  mixed  cheese  and  sand  to  the  extraction  tube,  wash  out 
the  mortar  with  ether,  add  the  washings  to  the  tube  and  continue 
the  extraction  for  at  least  ten  hours.     Dry  the  fat  at  105°  C.,  cool 
in  desiccator  and  weigh. 


454  TECHNICAL  METHODS  OF  ANALYSIS 

REFERENCE.  —  J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis 
(1916),  page  296. 

VINEGAR 

Preparation  of  Sample. — Before  starting  the  analysis  note  the 
appearance,  color,  odor  and  taste.  For  microscopical  examina- 
tion employ  the  original  sample,  but  for  chemical  analysis  filter 
if  turbid. 

Calculation  of  Results. — Express  all  results  in  grams  per  100 
cc.,  unless  otherwise  noted. 

Specific  Gravity. — Determine  the  sp.  gr.  at  15.5°  C.  by  means 
of  a  pycnometer,  a  small  accurately  graduated  hydrometer,  or  a 
Westphal  plummet  on  the  analytical  balance.  If  a  pycnometer  is 
used,  it  should  be  warmed  quickly  to  room  temperature  after 
filling  and  before  weighing,  to  prevent  the  error  due  to  collection 
of  moisture  on  the  outside.  A  small  hole  filed  in  the  cap  will 
permit  the  necessary  expansion  in  the  volume  of  the  liquid. 

Alcohol. — Measure  100  ce.  of  the  sample  into  a  round-bottom 
distilling  flask  and  make  faintly  alkaline  with  saturated  NaOH 
solution.  Add  a  small  scrap  of  paraffin,  distill  nearly  50  cc.  and 
make  up  the  distillate  to  50  cc.  at  the  temperature  of  the  sample. 
Filter  if  necessary  and  determine  the  sp.  gr.  with  a  pycnometer. 
Calculate  the  grams  of  alcohol  per  100  cc.  from  standard  alcohol 
tables  *  bearing  in  mind  that  the  alcohol  strength  of  the  distillate 
is  twice  that  of  the  original  vinegar. 

GlyceroL — When  it  is  necessary  to  determine  the  amount  of 
glycerol,  use  the  method  described  in  J.  Assoc.  Official  Agr. 
Chemists,  Methods  of  Analysis  (1916),  page  253. 

Total  Solids  (Tentative). — Measure  10  cc.  of  filtered  vinegar 
into  a  weighed  flat-bottomed  platinum  dish  of  50  mm.  bottom 
diameter.  Evaporate  on  a  boiling  water  bath  to  a  thick  syrup  t 
and  dry  for  exactly  2.5  hours  in  the  drying  oven  at  the  temperature 
of  boiling  water.  Cool  in  a  desiccator  and  weigh. 

NOTE.— It  is  essential  to  use  a  flat-bottomed  dish.  We  have  found,  how- 
ever, that  silica  dishes  may  be  used  in  place  of  platinum. 

*  Leach:  "Food  Inspection  and  Analysis,"  3d  Ed.,  page  661,  4th  Ed. 
page  690;  Van  Nostrand's  "  Chemical  Annual";  J.  Assoc.  Official  Agr. 
Chemists,  Methods  of  Analysis  (1916),  page  194;  Bureau  of  Standards, 
Circular  19. 

fThis  should  require  30  minutes. 


ANALYSIS  OF  FOODSTUFFS  455 

Total  Reducing  Substances  before  Inversion.— Proceed  accord- 
ing to  Munson  and  Walker's  Method  (page  403),  using  10  or 
20  cc.  of  the  sample;  express  results  as  grams  of  invert  sugar  per 
100  cc.  Malt  vinegar  should  be  clarified  with  sodium  phospho- 
tungstate.  In  the  case  of  malt  vinegar,  express  the  results  as 
dextrose;  in  all  other  cases,  as  invert  sugar. 

Reducing  Sugars  before  Inversion,  after  Evaporation. — 
Evaporate  50  cc.  on  the  water  bath  to  5  cc.  Add  25  cc.  of  water 
and  evaporate  to  5  cc.  Again  add  25  cc.  of  water  and  evaporate 
to  5  cc.  Transfer  to  a  100  cc.  volumetric  flask,  make  up  to  the 
mark  and  proceed  as  in  the  preceding  paragraph,  using  a  quantity 
equivalent  to  10  or  20  cc.  of  the  sample. 

Reducing  Sugars  after  Inversion. — Proceed  as  in  the  preceding 
paragraph  and,  after  the  last  evaporation  to  5  cc.,  transfer  to  a 
100  cc.  flask  with  70  cc.  of  water.  Clarify  with  basic  lead  acetate 
solution  and  alumina  cream,  and  invert  the  solution  with  HC1 
as  described  on  page  400  under  the  Determination  of  Sucrose  in 
the  Absence  of  Raffinose  by  Polarization  before  and  after  Inver- 
sion. Nearly  neutralize  with  NaOH  solution,  make  up  to  the 
mark  and  determine  the  reducing  sugars  by  the  Munson  and 
Walker  method  (page  403),  taking  an  aliquot  equivalent  to  10 
or  20  cc.  of  the  sample. 

Lead  Precipitate. — To  10  cc.  of  the  sample  in  a  test  tube  add 
2  cc.  of  20%  lead  acetate  solution,  shake  and  let  stand  30  minutes. 
Describe  the  precipitate  as  turbid,  light,  normal,  heavy  or  very 
heavy. 

Polarization. — If  the  lead  precipitate  is  normal,  add  to  50  cc. 
of  the  sample  5  cc.  of  basic  lead  acetate  solution.  Shake  and  let 
stand  30  minutes;  filter  and  polarize,  preferably  in  a  200  mm.  tube, 
correcting  for  dilution.  If  basic  lead  acetate  gives  only  a  turbidity, 
add  to  the  sample,  already  treated  with  basic  lead  acetate,  10  cc. 
of  alumina  cream,  shake,  let  stand  30  minutes,  filter  and  polarize, 
correcting  for  dilution.  (See  pages  397-399.) 

In  the  case  of  malt  vinegar,  treat  100  cc.  of  the  sample  with 
5  cc.  of  10%  phosphotungstic  acid  solution  and  filter.  To  50  ec. 
of  the  filtrate  add  5  cc.  of  the  basic  lead  acetate  solution,  filter 
and  polarize,  correcting  the  reading  obtained  for  dilution.  (See 
also  Leach:  "Food  Inspection  and  Analysis"  (1911  Edition),  pages 
578  and  769). 


456  TECHNICAL  METHODS  OF  ANALYSIS 

Ash.— Measure  25  cc.  into  a  weighed  platinum  dish.  Evapo- 
rate to  dryness  on  the  steam  bath  and  heat  to  a  char  at  low  heat. 
Treat  the  charred  portion  with  a  few  cc.  of  water  and  filter  through 
a  quantitative  filter.  Ignite  the  filter  paper  and  carbon  in  the 
platinum  dish  at  low  heat.  Add  the  filtrate  and  evaporate  to 
dryness.  Ignite  gently  and  weigh.  At  no  time  allow  the  temper- 
ature to  exceed  a  dull  red. 

NOTE. — Useful  information  may  often  be  obtained  by  noting  the  odor 
given  off  by  the  solids  during  charring. 

Soluble  and  Insoluble  Ash  and  Alkalinity. — Add  to  the  above 
ash  10-15  cc.  of  water,  bring  nearly  to  a  boil  and  filter  through 
a  9  cm.  quantitative  filter.  Wash  with  successive  portions  of 
hot  water  until  the  filtrate  measures  about  60-75  cc.  Dry  and 
ignite  the  filter  with  the  undissolved  residue  at  low  red  heat  in 
the  platinum  dish.  Cool,  weigh  and  calculate  as  insoluble  ash. 
Subtract  from  the  total  ash  to  obtain  the  soluble  ash.  Cool  the 
filtrate  and  titrate  with  0.1  N  HC1  and  methyl  orange.  Express 
the  alkalinity  of  the  soluble  ash  as  the  number  of  cc.  of  0.1  N  HC1 
per  100  cc.  of  sample. 

Soluble  and  Insoluble  Phosphoric  Acid. — Determine  the  P20s 
in  the  water-soluble  and  water-insoluble  portions  of  the  ash  by 
the  official  method  for  Fertilizers,  (page  525),  dissolving  the  water- 
insoluble  portion  in  about  50  cc.  of  boiling  HNOa  (1  :  9).  Express 
results  as  milligrams  of  P205  per  100  cc.  of  vinegar. 

Total  Acids. — Dilute  10  cc.  of  the  sample  with  recently  boiled 
and  cooled  water  until  it  appears  very  slightly  colored  and  titrate 
with  0.5  N  NaOH  and  phenolphthalein.  Calculate  results  to 
acetic  acid.  For  most  purposes  it  is  customary  to  report  as  Total 
Acidity,  Calculated  as  Acetic  Acid. 

CALCULATION. — 1  cc.  of  0.5  N  NaOH  =  0.0300  gram  acetic  acid. 

NOTE. — Instead  of  using  0.5  N  NaOH  to  titrate  10  cc.,  the  10  cc.  may  be 
diluted  in  a  graduated  flask  to  250  cc  and  50  cc.  of  this  solution  titrated  with 
0.1  N  NaOH-  (1  cc.  0.1  N  NaOH  =  0.00600  gram  acetic  acid). 

Fixed  Acids. — Measure  10  cc.  into  a  200  cc.  porcelain  casserole. 
Evaporate  just  to  dryness,  add  5-10  cc.  of  water,  and  again  evapo- 
rate. Repeat  until  at  least  five  evaporations  have  taken  place 
and  no  odor  of  acetic  acid  can  be  detected.  Add  about  200  cc. 


ANALYSIS  OF  FOODSTUFFS  457 

of  recently  boiled,  distilled  water  and  titrate  with  0.1  N  NaOH 
and  phenolphthalein.  Express  the  result  as  malic  acid. 

CALCULATION. — 1  cc.  0.1  N  NaOH  =  0.0067  gram  malic  acid. 

Volatile  Acids. — Calculate  the  fixed  acid  as  acetic  and  sub- 
tract from  the  total  acid,  also  calculated  as  acetic.  Report  the 
difference  as  Volatile  Acids,  Calculated  as  Acetic  Acid. 

Esters.* — Dilute  200  cc.  of  the  sample  with  25  cc.  of  water  and 
distill  slowly  into  a  graduated  200  cc.  flask  until  nearly  filled 
to  the  mark.  Complete  the  volume  and  mix  well.  Exactly 
neutralize  50  cc.  of  the  distillate  to  phenolphthalein  with  0.1  N 
NaOH,  and  add  a  measured  excess  of  25-50  cc.  of  the  0.1  N  NaOH 
over  the  amount  required  for  neutralization.  Either  boil  for  one 
hour  with  a  reflux  condenser,  or  let  stand  overnight  in  a  stoppered 
flask,  and  then  heat  with  a  tube  condenser  for  one-half  hour  below 
the  boiling  point.  Cool,  and  titrate  the  excess  of  NaOH  with 
0.1  N  acid  and  phenolphthalein.  Multiply  the  number  of  cc.  of 
0.1  N  NaOH  consumed  in  the  saponification  by  0.0088,  thus 
obtaining  the  grams  of  esters,  calculated  as  ethyl  acetate.  Mul- 
tiply this  by  2  to  bring  to  the  basis  of  100  cc.  Also  report  the 
ester  number,  which  is  the  milligrams  of  KOH  required  to  saponify 
the  esters  in  1  gram  of  the  sample.  For  this  purpose  1  gram  of 
vinegar  may  be  considered  equivalent  to  1  cc. 

Formic  Acid  (Fincke  Method). — To  100  cc.  of  the  sample  add 
0.4-0.5  gram  of  tartaric  acid  and  distill  with  steam.  Pass  the 
outflowing  stream  through  a  boiling  mixture  of  15  grams  of  CaCOs 
and  100  cc.  of  water  and  keep  this  volume  constant  throughout 
the  process.  Keep  the  volume  of  the  solution  in  the  sample  flask 
down  to  30-40  cc.  by  heating  with  a  small  Tirrill  flame.  Collect 
1000  cc.  of  distillate.  Discard  the  distillate,  disconnect  the 
apparatus,  filter  the  CaCOs  mixture  and  wash  with  a  little  hot 
water.  Make  the  filtrate  slightly  acid  with  HC1,  add  10-15  cc. 
of  mercuric  chloride  solution  (10  grams  of  HgCb  and  3  grams  of 
NaCl  to  100  cc.).  Heat  in  a  boiling  water  bath  for  two  hours, 
filter  on  a  weighed  Gooch  crucible,  wash  the  precipitate  thoroughly 
with  cold  water,  then  with  a  little  alcohol  and  finally  with  ether. 
Dry  in  a  boiling  water  oven  for  thirty  'minutes,  cool  in  a  desic- 
cator and  weigh  as  mercurous  chloride.  Calculate  to  formic  acid. 

*  This  is  not  a  method  of  the  Association  of  Official  Agricultural 
Chemists. 


458  TECHNICAL  METHODS  OF  ANALYSIS 

CALCULATION. — Hg2Cl2  X  0.097  =  formic  acid. 

NOTES. — (1)  The  determinations  usually  required  on  a  sample  of  vinegar, 
are  sp.  gr.,  total  solids,  and  total  acidity  calculated  as  acetic  acid. 

(2)  For  other  determinations  than  above   described    (alcohol  precipitate, 
pentosans,  tartaric  acid,  free  mineral  acid,  dextrin,  spices,  coloring  matters, 
preservatives,  etc.)  see  J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis 
(1916;  page  253. 

(3)  This  method  conforms  to  the  requirements  of  the  Massachusetts 
Board  of  Health's  Regulations  for  Testing  Vinegar. 

(4)  The  Massachusetts  standards  for  Cider  Vinegar  (Chapter  145,  Gen- 
eral Acts  of  the  Legislature,  1918)  are  as  follows:   "  It  shall  contain  no  added 
or  artificial  coloring  and  not  less  than  4  grams  of  acetic  acid  in  100  cc.  "  These 
are  the  same  requirements  as  the  Federal  standard  (Circular  19)  which  in 
addition  states  that  it  shall  be  laevo-rotatory;  that  not  more  than  50%  of  the 
solids  shall  be  reducing  sugars;    that  the  ash  shall  not  be  less  than  0.25  gram 
in  100  cc.;  and  that  the  water-soluble  ash  from  100  cc.  shall  contain  not  less 
than  10  mg.  of  ?2O5  and  require  not  less  than  30  cc.  of  0.1  N  acid  to 
neutralize  its  alkalinity. 

(5)  The  above  methods,  unless  otherwise    indicated,  are  the  tentative 
methods  of  the  Association  of  Official  Agricultural  Chemists  (J.  Assoc.  Official 
Agr.  Chemists,  Methods  of  Analysis  (1916),  page  253). 


LEMON  AND  ORANGE  EXTRACTS 

Specific  Gravity. — Determine  the  sp.  gr.  at  15.5°  C.  with  a 
pycnometer,  compared  with  H^O  at  the  same  temperature. 

Alcohol. — Dilute  50  cc.  of  the  extract,  measured  at  15.5°  C., 
in  a  200  cc.  volumetric  flask  nearly  to^the  mark.  Let  stand  until 
the  oil  separates  to  a  clear  layer  on  top  (or  if  necessary,  centrifugal- 
ize).  Then  make  up  to  the  mark  at  15.5°  C.,  using  the  lower 
meniscus  of  the  oil.  Pour  the  mixture  into  a  dry  Erlenmeyer 
flask  containing  5  grams  of  light  MgCOs,  stopper,  shake  well  and 
filter  quickly  through  a  large  dry  folded  filter.  Determine  the 
alcohol  in  the  filtrate  as  follows: 

(a)  BY  WEIGHT. — Place  150  cc.  of  the  filtrate,  measured  at 
15.5°  C.,  in  a  300-500  cc.  distilling  flask.  Attach  the  flask  to  a 
vertical  condenser  and  distill,  catching  the  distillate  in  a  100  cc. 
graduated  flask.  Stop  the  distillate  when  nearly  100  cc.  have  been 
distilled.  Make  up  to  the  mark  with  water  at  15.5°  C.  and  mix 
thoroughly.  Determine  the  sp.  gr.  accurately  with  a  pycnometer. 
Ascertain  from  standard  alcohol  tables  the  percentage  of  alcohol 
by  weight  corresponding  to  the  sp.  gr.  of  the  distillate.  Multiply 


ANALYSIS  OF  FOODSTUFFS  459 

this  figure  by  the  weight  of  the  distillate  (its  volume  Xsp.  gr.) 
and  divide  by  the  weight  of  the  sample  in  the  aliquot  taken,  i.e., 
37. 5  X  its  sp.  gr. 

(6)  BY  VOLUME. — From  the  sp.  gr.  of  the  distillate,  obtained  as 
above,  ascertain  the  per  cent  of  alcohol  by  volume  from  the  alcohol 
tables.  Multiply  this  figure  by  the  volume  of  distillate  and  divide 
by  the  volume  of  the  original  sample,  i.e.,  37.5. 

NOTES. — (1)  References  to  standard  alcohol  tables  are  given  on  page  454. 

(2)  In  case  alcohol  tables  are  used  which  are  based  on  a  gravity  at  some 
other  temperature  than  15.5°  C.,  the  sp.  gr.  of  the  original  sample  and  of  the 
alcohol  distillate  must  both  be  determined  at  the  same  temperature  as  that 
on  which  the  tables  are  based. 

Glycerol. — Evaporate  100  cc.  of  the  extract  *  in  a  porcelain 
dish  on  a  water  bath  to  a  volume  of  about  10  cc.,  treat  the 
residue  with  about  5  grams  of  fine  sand  and  3-4  cc.  of  milk  of 
lime  (containing  about  15%  of  CaO)  for  each  gram  of  extract 
present,  and  evaporate  almost  to  dryness.  Treat  the  moist 
residue  with  50  cc.  of  90%  alcohol  by  volume,  remove  the  sub- 
stance adhering  to  the  sides  of  the  dish  with  a  spatula,  and  rub 
the  whole  mass  to  a  paste.  Heat  the  mixture  on  the  water  bath, 
with  constant  stirring,  to  incipient  boiling  and  decant  the  liquid 
through  a  filter  into  a  small  flask.  Wash  the  residue  repeatedly 
by  decantation  with  10  cc.  portions  of  hot  90%  alcohol  until  the 
filtrate  amounts  to  about  150  cc.  Evaporate  the  filtrate  to  a 
syrupy  consistency  in  a  porcelain  dish,  on  a  hot,  but  not  boiling, 
water  bath;  transfer  the  residue  to  a  small  glass  stoppered  grad- 
uated cylinder  with  20  cc.  of  absolute  alcohol  and  add  three  por- 
tions of  10  cc.  each  of  absolute  ether,  thoroughly  shaking  after 
each  addition.  Let  stand  until  clear,  then  pour  off  through  a 
filter  and  wash  the  cylinder  and  filter  with  a  mixture  of  1  part 
of  absolute  alcohol  and  1.5  parts  of  absolute  ether,  pouring  the 
wash  liquor  also  through  the  filter.  Evaporate  the  filtrate  to  a 
syrupy  consistency,  dry  for  one  hour  at  the  temperature  of  boiling 
water,  weigh,  ignite  and  weigh  again.  The  loss  on  ignition  gives 
the  weight  of  glycerol. 

*  If  100  cc.  contain  more  than  0.4  gram  of  glycerol,  use  a  smaller  amount. 


460  TECHNICAL  METHODS   OF  ANALYSIS 

Lemon  and  Orange  Oils. — (a)  BY  POLARIZATION  (MITCHELL). 
— Polarize  the  extract  at  20°  C.  without  dilution  in  a  200  mm.  tube 
and  divide  the  reading  in  degrees  Ventzke  by  3.2,  in  the  case  of 
lemon  extract,  and  by  5.2,  in  the  case  of  orange  extract.  In  the 
absence  of  other  optically  active  substances,  the  result  will  be 
the  percentage  of  oil  by  volume.  A  small  amount  of  cane  sugar  is 
occasionally  present ;  if  so,  determine  it  as  directed  under  Sucrose 
and  correct  the  reading  accordingly. 

(6)  BY  PRECIPITATION  (MITCHELL). — Pipette  20  cc.  of  the 
extract  into  a  Babcock  milk  bottle;  add  1  cc.  of  dil.  HC1  (1  :  1); 
then  add  25-28  cc.  of  water  previously  warmed  to  60°  C,;  mix 
and  let  stand  in  water  at  60°  for  five  minutes;  whirl  in  a  centrifuge 
for  five  minutes;  fill  with  warm  water  to  bring  the  oil  into  the 
graduated  neck  of  the  flask;  repeat  the  whirling  for  two  minutes; 
stand  the  flask  in  water  at  60°  C.  for  a  few  minutes  and  read 
the  per  cent  of  oil  by  volume.  In  case  oil  of  lemon  is  present  in 
amounts  over  2%,  add  to  the  percentage  of  oil  found  0.4%,  to  cor- 
rect for  the  oil  retained  in  solution.  If  less  than  2%  and  more 
than  1%  is  present,  add  0.3%  for  correction. 

To  obtain  the  per  cent  by  weight  from  the  per  cent  by  volume, 
as  found  by  either  of  the  above  methods,  multiply  the  volume 
percentage  by  0.86*  and  divide  the  result  by  the  sp.  gr.  of  the 
original  extract. 

Total  Aldehydes  (Chace  Method). — (a)  REAGENTS. 

(1)  Aldehyde-free  Alcohol. — Allow  alcohol  (95%  by  volume), 
containing  5   grams    of  m-phenylenediamine   hydrochloride   per 
liter,  to  stand  for  twenty-four  hours  with  frequent  shaking.     Boil 
under  a  reflux  condenser  for  at  least  eight  hours  (longer  if  neces- 
sary),   let  stand  overnight  and    distill,  rejecting    the  first  10% 
and  the  last   5%  which  come  over.     Keep  in  a  dark,  cool  place 
in  well-filled  bottles.  25  cc.  of  this  alcohol  on  standing  for  twenty 
minutes  in  a  cooling  bath  at  14-16°  C.  with  20  cc.  of  fuchsin 
solution  should  develop  only  a  faint  pink  coloration.     If  a  stronger 
color  is  developed,  treat  it  again  with  m-phenylenediamine  hydro- 
chloride. 

(2)  Sulfite-fuchsin  Solution. — Dissolve  0.5    gram    of    fuchsin 
in  250  cc.  of  water,  add  an  aqueous  solution  of  862  containing 
16  grams  of  the  gas  and  let  stand  until  colorless  or  nearly  so. 

*  This  is  for  lemon  oil;  use  0.85  for  orange. 


ANALYSIS  OF  FOODSTUFFS  461 

Then  make  up  to  1  liter  with  distilled  water.  This  solution  should 
stand  twelve  hours  before  using.  It  should  be  kept  in  a 
refrigerator  and  discarded  after  three  days. 

(3)  Standard  Citral  Solution. — Use  0.5  or  1.0  mg.  of  c.  P.  citral 
per  cc.  in  50%  by  volume  of  aldehyde-free  alcohol. 

(6)  MANIPULATION. — Weigh  in  a  stoppered  weighing  bottle 
approximately  25  grams  of  extract,  transfer  to  a  50  cc.  volumetric 
flask,  and  make  up  to  the  mark  at  room  temperature  with  alde- 
hyde-free alcohol.  Measure  at  room  temperature  2  cc.  of  this 
solution  into  a  comparison  tube.  Add  25  cc.  of  the  aldehyde- 
free  alcohol  (previously  cooled  to  14-16°  C.),  then  20  cc.  of  the 
sulfite-fuchsine  solution  (also  cooled)  and  finally  make  up  to  the 
50  cc.  mark  with  more  aldehyde-free  alcohol.  Mix  thoroughly, 
stopper,  and  keep  at  14-16°  C.  for  fifteen  minutes.  Prepare  a 
standard  for  comparison  at  the  same  time  and  in  the  same  manner, 
using  2  cc.  of  the  standard  citral  solution,  and  compare  the  colors 
developed.  Calculate  the  amount  of  citral  present.  Repeat  the 
determination,  using  a  quantity  sufficient  to  give  the  sample 
approximately  the  strength  of  the  standard.  From  this  result 
calculate  the  amount  of  citral  in  the  sample.  If  the  comparisons 
are  made  with  Nessler  tubes,  standards  containing  1,  1.5,  2,  2.5, 
3,  3.5,  and  4  mg.,  respectively,  of  citral  should  be  prepared  and 
the  trial  comparisons  made  against  these,  the  final  comparison 
being  made  with  standards  between  1.5  and  2.5  mg.  with  0.25  mg. 
increments. 

NOTE. — It  is  absolutely  essential  to  keep  the  reagents  and  the  comparison 
tubes  at  the  required  temperature.  Comparisons  should  be  made  within  one 
minute  after  removing  the  tubes  from  the  bath.  Give  the  samples  and 
standards  identical  treatment. 

Citral   (Hiltner  Method). — (a)  REAGENTS. 

(1)  m-Phenylenediamine  Hydrochloride  Solution. — Prepare  a  1% 
solution    of  m-phenylenediamine    hydrochloride   in    95%    ethyl 
alcohol.     Decolorize  if  necessary  by  shaking  with  fuller's  earth 
and  filter  through  a  double  filter.     The  solution  should  be  bright 
and  clear,  free  from  suspended  matter,  and  practically  colorless. 
It  is  well  to  prepare  only  enough  solution  for  the  day's  work,  as 
it  darkens  on  standing. 

(2)  Alcohol. — For    the    analysis    of    lemon  extracts,  90-95% 
alcohol  should  be  used,  but  for  terpeneless  extracts  alcohol  of 


462  TECHNICAL  METHODS  OF  ANALYSIS 

40-50%  strength  is  sufficient.  Filter  to  remove  any  suspended 
matter.  The  alcohol  need  not  be  purified  from  aldehyde.  If 
not  practically  colorless,  render  slightly  alkaline  with  NaOH  and 
distill. 

(6)  MANIPULATION. — All  of  the  operations  may  be  carried 
on  at  room  temperature.  Weigh  25  grams  of  the  extract  into  a 
50  cc.  graduated  flask  and  make  up  to  the  mark  with  alcohol. 
Stopper  the  flask  and  mix  the  contents  thoroughly.  Pipette  2  cc. 
of  this  solution  into  a  Nessler  tube,  add  10  cc.  of  ra-phenylene- 
diamine  hydrochloride  reagent  and  complete  the  volume  to  50  cc. 
with  alcohol.  Compare  at  once  the  color  with  that  of  the  standard 
prepared  at  the  same  time,  using  2  cc.  of  standard  citral  solution 
and  10  cc.  of  the  m-phenylenediamine  reagent,  and  diluting  to 
volume  with  alcohol.  From  the  result  of  this  first  determination 
calculate  the  amount  of  standard  citral  solution  that  should  be 
used  in  order  to  give  approximately  the  same  citral  strength  of 
the  sample  under  examination,  then  repeat  the  comparison  against 
the  new  standard. 

Total  Solids. — Evaporate  nearly  to  dryness  10  cc.  of  the  sam- 
ple in  a  flat  platinum  dish  on  a  water  bath  at  a  low  temperature. 
Heat  the  residue  for  two  and  one-half  hours  in  a  drying  oven  at  the 
temperature  of  boiling  water,  cool  and  weigh. 

Ash. — Burn  the  residue  from  10  cc.  of  the  extract  to  a  white 
ash  at  the  lowest  possible  heat,  cool  and  weigh. 

Sucrose. — Neutralize  the  normal  weight  of  the  extract,  evap- 
orate to  dryness,  wash  several  times  with  ether,  dissolve  in  water 
and  determine  sucrose  in  the  usual  manner  by  means  of  a  polari- 
scope  (page  400),  or  by  copper  reduction  (page  402). 

Methyl  Alcohol  (Riche  and  Bardy). — Test  the  distillate  ob- 
tained in  the  determination  of  Alcohol  above  for  methyl  alcohol  as 
follows:  Place  10  cc.  in  a  small  flask  with  15  grams  of  iodine  and 
2  grams  of  red  phosphorus.  Keep  in  ice  water  for  ten  to  fifteen 
minutes  until  action  has  ceased.  Distill  off  on  the  water  bath 
the  methyl  and  ethyl  iodides  formed  into  about  30  cc.  of  water. 
Wash  with  dilute  NaOH  to  eliminate  free  iodine,  separate  the 
heavy  oily  liquid  which  settles  and  transfer  to  a  flask  containing 
5  cc.  of  aniline.  If  the  action  is  too  violent,  place  the  flask  in 
cold  water;  if  too  slow,  warm  the  flask.  After  one  hour,  boil  the 
product  with  water  and  add  about  20  cc.  of  15%  NaOH  solution. 


ANALYSIS  OF  FOODSTUFFS  463 

When  the  bases  rise  to  the  top  as  an  oily  layer,  fill  the  flask  up  to 
the  neck  with  water  and  draw  them  off  with  a  pipette.  Oxidize 
1  cc.  of  the  oily  liquid  by  adding  10  grams  of  a  mixture  of  100 
parts  of  clean  sand,  2  of  common  salt  and  3  of  cupric  nitrate. 
Mix  thoroughly,  transfer  to  a  glass  tube  and  heat  to  90°  C.  for 
eight  to  ten  hours.  Exhaust  the  product  with  warm  alcohol, 
filter  and  make  up  to  100  cc.  with  alcohol.  In  the  presence  of 
ethyl  alcohol  free  from  methyl  alcohol  the  liquid  has  a  red  tint, 
but  in  the  presence  of  1%  of  methyl  alcohol  it  has  a  distinct  violet 
shade;  with  2.5%  the  shade  is  very  distinct,  and  still  more  so 
with  5%.  To  detect  more  minute  quantities  of  methyl  alcohol, 
dilute  5  cc.  of  the  colored  liquid  to  100  cc.  with  water,  and  dilute 
5  cc.  of  this  again  to  400  cc.  Heat  the  liquid  thus  obtained  in  a 
porcelain  dish  and  immerse  in  it  a  fragment  of  white  merino 
yarn  (free  from  sulfur)  for  thirty  minutes.  If  the  ethyl  alcohol 
is  pure,  the  wool  will  remain  white,  but  if  methyl  alcohol  is  present, 
it  will  become  violet,  and  the  depth  of  the  tint  will  give  a  fairly 
approximate  indication  of  the  proportion  of  methyl  alcohol 
present. 

NOTE. — The  presence  of  methyl  alcohol  and  its  approximate  amount 
may  also  be  ascertained  by  determining  the  refraction  at  20°  C.  with  the  im- 
mersion refractometer.  (See  J.  Assoc.  Official  Agr.  Chemists,  Methods  of 
Analysis  (1916),  page  247.) 

Detection  of  Coloring  Matter. — (a)  LEMON  AND  ORANGE  PEEL 
COLOR  (ALBRECH  METHOD). — Place  a  few  cc.  of  the  extract  in  a 
test-tube  and  add  slowly  3—4  volumes  of  cone.  HC1.  Place  a  few 
cc.  of  the  extract  in  a  second  tube  and  add  several  drops  of  cone. 
NH4OH.  If  the  color  is  due  to  the  presence  of  lemon  or  orange 
peel  only,  it  is  materially  deepened  in  both  cases. 

(6)  TURMERIC. — Evaporate  25-50  cc.  of  the  extract  upon  a 
small  piece  of  filter  paper,  dry  at  low  temperature,  and  moisten 
with  a  weak  solution  of  boric  acid  containing  a  small  amount  of 
HC1.  Upon  drying  a  second  time  a  cherry  red  color,  changing  to 
green  when  spotted  with  NELiOH,  develops  in  the  presence  of 
turmeric. 

REFERENCE. — J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis 
(1916),  page  261. 


464  TECHNICAL  METHODS  OF  ANALYSIS 


ORANGE  OIL  AND  LEMON  OIL 

Specific  Gravity. — Determine  the  sp.  gr.  at  15.5°  C.  with  a 
Westphal  balance. 

Refractive  Index. — Determine  the  refractive  index  at  20°  C. 
with  the  Abbe  refractometer. 

Optical  Rotation. — Determine  the  rotation  at  20°  C.  with  any 
standard  instrument,  using  a  50  mm.  water-jacketed  tube  and 
sodium  light.  The  results  should  be  stated  in  angular  degrees  on  a 
100  mm.  basis.  If  instruments  having  the  sugar  scale  are  used, 
the  reading  on  orange  oil  is  above  the  range  of  the  scale,  but  read- 
ings may  be  obtained  by  the  use  of  standard  laevo-rotatory  quartz 
plates  or  by  the  use  of  a  25  mm.  tube.  The  true  rotation  cannot 
be  obtained  by  diluting  the  oil  with  alcohol  and  correcting  pro- 
portionately. 

Citral  (Hiltner  Method). — Proceed  as  directed  under  Lemon 
and  Orange  Extracts  (page  461),  weighing  2  grams  of  lemon  oil  or 
8  grams  of  orange  oil  into  a  100  cc.  volumetric  flask,  diluting  to 
100  cc.  with  95%  alcohol  by  volume  and  using  2  cc.  of  this  solution 
for  the  comparison. 

Total  Aldehydes. — Weigh  a  small  quantity  of  the  sample  into  a 
small  stoppered  flask  and  dilute  with  aldehyde-free  alcohol  in  the 
proportion  of  2  grams  of  lemon  oil  or  4  grams  of  orange  oil  to  100 
cc.  of  solution.  Determine  the  total  aldehydes  as  described  on 
page  460  for  Orange  and  Lemon  Extracts  (Chace  Method), 
expressing  the  result  as  citral. 

REFERENCE. — J.  Assoc.  Official  Agr.  Chemists,  Methods  of  Analysis 
(1916),  page  264. 


OIL  OF  PEPPERMINT 

Specific  Gravity. — Determine  the  sp.  gr.  at  20°  C.  with  a 
Westphal  balance. 

Refractive  Index. — Determine  the  refractive  index  with  the 
Abbe  refractometer  at  25°  C. 

Specific  Rotation,  [a]™. — Determine  the  angle  of  refraction  by 
means  of  the  polariscope.  Have  the  temperature  exactly  20°  C. 


ANALYSIS  OF  FOODSTUFFS  465 

and  use  a  sodium  light.*   Calculate  the  specific  rotation,  [a]??,  from 
the  following  formula : 

20_^  100 

-ZXsp.gr.at200d 

where   a  =  angle  of  refraction, 
and      L  =  length  of  tube  in  mm. 

Dimethyl  Sulfide. — Distill  1  cc.  from  25  cc.  of  oil  and  pour  the 
distillate  on  an  aqueous  solution  of  HgCk.  A  white  film  forming 
after  a  short  time  at  the  zone  of  contact  indicates  dimethyl  sulfide, 
which  is  found  in  non-rectified  oils. 

Menthyl  Esters.— Saponify  8-10  grams  of  oil  by  boiling  for 
one  hour  with  25  cc.  of  0.5  N  alcoholic  KOH  in  a  flask  provided 
with  a  reflux  condenser.  After  cooling,  titrate  with  0.5  N  HC1 
and  phenolphthalein. 

Multiply  the  number  of  cc.  of  KOH  consumed  in  the  saponi- 
fication  by  9.9  and  divide  the  product  by  tfee  weight  of  oil  taken. 
This  gives  percentage  of  esters  as  menthyl  acetate. 

Total  Menthol. — Wash  the  residual  oil  from  the  ester  deter- 
mination with  water  a  number  of  times,  transfer  to  an  acetyliza- 
tion  flask  (preferably  a  flask  with  a  ground  glass  tube  condenser), 
add  .10  cc.  of  acetic  anhydride  and  1  gram  of  anhydrous  sodium 
acetate,  and  boil  gently  for  one  hour.  Cool,  wash  the  acetylized 
oil  with  water,  and  then  with  very  dilute  NaOH  solution,  until 
the  mixture  is  slightly  alkaline  to  phenolphthalein.  Separate  the 
oil  from  any  water  in  a  separatory  funnel,  pour  into  a  small  flask, 
add  a  few  pieces  of  fused  CaCk,  let  stand  for  several  hours,  and 
filter. 

Weigh  out  3-6  grams  of  this  dry  oil  in  an  Erlenmeyer  flask 
and  saponify  by  boiling  for  one  hour  with  50  cc.  of  0.5  N  alcoholic 
KOH.  After  cooling,  titrate  the  excess  alkali  with  0.5  N  HC1. 

Each  cc.  of  0.5  N  alcoholic  KOH  corresponds  to  0.0781  gram 
of  menthol,  or  0.0991  gram  of  menthyl  acetate.  In  order,  there- 
fore, to  obtain  the  percentage  of  menthol  in  the  original  oil  (not 
acetylized  but  freed  from  ester),  it  is  necessary  to  deduct  0.0210 

*  In  case  the  reading  is  taken  with  the  Ventzke  Saccharimeter,  using  gas  or 
other  white  light,  calculate  the  saccharimeter  reading  to  angular  reading  by 
multiplying  the  former  by  0.3468. 


466  TECHNICAL  METHODS  OF  ANALYSIS 

gram  (the  difference  between  0.0781  and  0.0991)  for  every  cc.  of 
0.5  N  alkali  consumed. 

The   following  formula,   therefore,   gives  the  total   menthol 
content  (free  and  ester) : 

7.81a 


P  = 


S-0.0210a' 


where   P  =  total  menthol  content; 
S  =  grams  of  acetylized  oil ; 
and        a  =  cc.  of  0.5  N  alkali  consumed. 

By  subtracting   the   amount   of   ester   as   first   determined,   the 
amount  of  free  menthol  is  obtained. 

NOTE. — The  chemistry  of  the  foregoing  method  is  as  follows: 

Menthol  is  a  saturated  secondary  alcohol  of  the  following  structural  formula. 

H3C       CH3 


CH 

I 
CH 


HiC\.       xCHa 

CH 

I 
CH3 

The  ester  has  the  formula: 

H3C       CH8 


Y 

CH 


CH 
H2Cf//\CHO-C2H30 


CH 

I 

CHi 


ANALYSIS  OF  FOODSTUFFS  467 

In  the  ester  determination  the  acetate  radical  is  removed  and  menthol 
formed  by  saponification.  The  menthol  is  then  all  transformed  to  the  ester 
by  the  action  of  acetic  anhydride  and  sodium  acetate.  This  compound  is 
then  saponified  back  to  menthol,  and  the  amount  of  alkali  consumed  gives  the 
amount  of  menthol  by  the  above  calculation. 

REFERENCES. — United  States  Pharmacopoeia;  United  States  Dispensa- 
tory; Gildemeister  and  Hoffmann:  "  The  Volatile  Oils." 


PEPPERMINT,  SPEARMINT  AND  WINTERGREEN  EXTRACTS 

Alcohol. — Since  these  extracts  usually  contain  only  about  1% 
of  oil,  the  alcohol  can  in  most  cases  be  calculated  from  the  sp.gr. 
of  the  extract.  If,  however,  the  extract  is  high  in  solids,  deter- 
mine the  alcohol  as  follows : 

Add  25  cc.  of  the  extract  to  75  cc.  of  a  saturated  solution 
of  NaCl  in  a  separatory  funnel  and  extract  twice  with  50  cc.  por- 
tions of  petroleum  ether  (b.  p.  40-60°  C.).  Collect  the  petroleum 
ether  extract  in  a  second  separatory  funnel  and  wash  twice  with 
two  separate  25  cc.  portions  of  saturated  brine.  Combine  the 
original  salt  solution  with  the  washings,  add  a  little  powdered 
pumice,  and  distill  into  a  100  cc.  volumetric  flask.  When  almost 
100  cc.  have  been  distilled,  make  up  to  the  mark  at  a  definite 
temperature  and  determine  the  alcohol  from  the  sp.  gr.  as  de- 
scribed on  page  458. 

NOTE. — A  50%  solution  of  CaCl2  may  be  used  in  place  of  saturated  brine. 

Oil  (Modified  Howard  Method).— Pipette  10  cc.  of  the  extract 
into  a  Babcock  milk  bottle,  add  1  cc.  of  CS2,  mix  thoroughly,  and 
then  add  25  cc.  of  cold  water  and  1  cc.  of  cone.  HC1.  Close  the 
mouth  of  the  bottle  and  shake  vigorously.  Centrifugalize  for 
six  minutes  and  remove  all  but  3-^4  cc.  of  the  supernatant  liquid, 
which  should  be  practically  clear,  by  aspirating  through  a  glass 
tube  of  small  bore.  Connect  the  stem  of  the  bottle  with  a  filter 
pump,  immerse  for  three  minutes  in  water  kept  at  about  70°  C., 
remove  from  the  bath  every  fifteen  seconds  and  shake  vigorously. 
Continue  in  the  same  manner  for  forty-five  seconds,  using  a 
boiling  water  bath.  Remove  from  the  bath  and  shake  while 
cooling.  Disconnect  from  the  suction  and  fill  the  bottle  to  the 
neck  with  saturated  NaCl  solution  at  room  temperature.  Cen- 
trifugalize for  two  minutes  and  read  the  volume  of  the  separated 


468  TECHNICAL  METHODS  OF  ANALYSIS 

oil  from  the  top  of  the  meniscus.  Multiply  the  reading  by  2  to 
obtain  the  per  cent  of  oil  by  volume. 

In  the  case  of  wintergreen  use  as  a  floating  medium  a  mixture 
of  1  volume  of  cone.  H2SO4  and  3  volumes  of  saturated  Na2S04 
solution. 

Methyl  Salicylate  in  Wintergreen  Extracts  (Modified  Hort- 
vet  and  West  Method). — Mix  10  cc.  of  the  extract  with  10  cc.  of 
10%  KOH  solution.  Heat  on  the  steam  bath  until  the  volume  is 
reduced  about  one-half.  Add  a  distinct  excess  of  HC1  (1  :  1), 
cool  and  extract  with  3  portions  of  ether,  40,  30  and  20  cc.,  respect- 
ively. Filter  the  extract  through  a  dry  filter  into  a  weighed  dish. 
Wash  the  paper  with  10  cc.  of  ether  and  allow  the  nitrate  and 
washings  to  evaporate  spontaneously.  Dry  in  a  desiccator  con- 
taining H2&04  and  weigh.  Multiply  the  weight  of  salicylic  acid 
thus  found  by  9.33  to  obtain  the  per  cent  by  volume  of  winter- 
green  oil  in  the  sample.  (Sp.  gr.  of  wintergreen  oil  =  1.178.) 

REFERENCE. — The  above  are  tentative  methods  of  the  Association  of 
Official  Agricultural  Chemists  as  published  in  its  Journal,  Methods  of 
Analysis  (1916),  page  268. 

VANILLA  EXTRACT 

Specific  Gravity. — Determine  at  15.5°  C.  by  means  of  a  West- 
phal  balance. 

Alcohol. — Weigh  into  a  distilling  flask  20-25  grams  of  the 
sample  and  dilute  with  100  cc.  of  water.  Distill  into  a  100  cc. 
volumetric  flask  through  a  vertical  condenser,  stopping  the  dis- 
tillation just  short  of  100  cc.  Make  up  to  volume  at  15.5°  C. 
and  determine  the  sp.  gr.  of  this  distillate  accurately  with  a  pyc- 
nometer  at  the  same  temperature.  Determine  the  per  cent  of 
alcohol  by  weight  and  by  volume  as  described  on  page  458. 

Determination  and  Identification  of  Vanillin  and  Coumarin. — 
The  determination  of  vanillin,  coumarin,  normal  lead  number  and 
residual  color  in  the  filtrate  are  all  to  be  made  on  one  weighed 
portion,  using  50  grams  of  the  sample.  For  the  determination  of 
coumarin  and  vanillin  employ  the  modified  Hess  and  Prescott 
method  as  follows: 

Weigh  50  grams  of  the  extract  directly  into  a  tared  250  cc. 
beaker  with  marks  showing  volumes  of  80  and  50  cc.  Dilute  to 


ANALYSIS  OF  FOODSTUFFS  469 

80  cc.  and  evaporate  to  50  cc.  in  a  water  bath  kept  at  70°  C. 
Dilute  again  to  80  cc.  with  water  and  evaporate  to  50  cc.  Trans- 
fer to  a  100  cc.  volumetric  flask,  rinsing  the  beaker  with  hot  water, 
add  25  cc.  of  8%  lead  acetate  solution,  make  up  to  the  mark  with 
water,  shake,  and  let  stand  eighteen  hours  (overnight)  at  37- 
40°  C.  This  can  best  be  obtained  by  means  of  an  incubating  oven. 
Decant  on  a  small  dry  filter,  pipette  off  50  cc.  of  filtrate,  and 
extract,  shaking  four  times  in  a  separatory  funnel,  using  50  cc.  of 
ether  first  and  then  15  cc.  three  times.  Wash  the  combined  ether 
solutions  four  or  five  times  with  2%  NHs  solution,  using  10  cc.  the 
first  time  and  5  cc.  thereafter.  Slightly  acidulate  the  combined 
ammoniacal  solutions  with  dil.  HC1,  cool  and  extract  in  a  sepa- 
ratory funnel  with  4  portions  of  ether,  using  about  40  cc.  in  all. 
Evaporate  the  ethereal  solutions  at  room  temperature,  dry  over 
cone.  H2S04  (more  quickly  accomplished  in  a  vacuum  desiccator) 
and  weigh.  If  the.  residue  is  considerably  discolored  or  gummy, 
re-extract  in  the  dry  state  with  boiling  petroleum  ether  (b.  p. 
40°  C.  or  below)  not  less  than  fifteen  times;  evaporate  the  solvent, 
dry  and  weigh.  The  residue  should  now  be  white,  crystalline 
vanillin  with  a  m.  p.  of  approximately  80°  C.  A  small  amount  of 
this  residue  dissolved  in  2  drops  of  cone.  HC1,  upon  the  addition 
of  a  crystal  of  resorcinol,  should  develop  a  pink  color. 

Evaporate  the  original  ether  extract  of  the  sample,  after  removal 
of  the  vanillin  with  NHiOH,  at  room  temperature,  and  dry  over 
cone.  H2SO4.  The  residue,  if  pure  coumarin,  should  melt  at 
approximately  67°  C.,  and  should  respond  to  Leach's  test  for 
coumarin  as  follows:  A  small  portion  of  the  residue  dissolved  in 
not  more  than  0.5  cc.  of  hot  water  should  develop  a  brown  pre- 
cipitate upon  the  addition  of  a  few  drops  of  0.1  N  iodine  solution. 
This  precipitate  finally  gathers  in  green  flocks,  leaving  a  clear 
brown  solution.  The  reaction  is  especially  marked  if  the  reagent 
is  applied  with  a  glass  rod  to  a  few  drops  of  the  solution  on  a  white 
plate  or  tile. 

NOTES. — (1)  For  extracting  the  coumarin  and  the  vanillin,  use  ether 
washed  with  water  at  least  twice  to  remove  alcohol. 

(2)  The  method  is  not  applicable  to  cone,  preparations  in  which  the  amount 
of  vanillin  and  coumarin  present  exceeds  the  quantity  dissolved  by  100  cc.  of 
H2O  at  20°  C.  In  such  cases  use  a  smaller  amount  of  the  sample  and  dilute 
to  50  cc. 


470  TECHNICAL  METHODS  OF  ANALYSIS 

Normal  Lead  Number.  —  To  an  aliquot  of  10  cc.  of  the  filtrate 
from  the  lead  acetate  precipitate  obtained  above,  add  25  cc.  of 
water,  0.5-1.0  cc.  of  cone.  H2SO4  and  100  cc.  of  95%  alcohol. 
Let  stand  overnight,  filter  on  a  Gooch  crucible,  wash  with  95% 
alcohol,  dry  at  a  moderate  heat  and  ignite  at  low  redness  for  three 
minutes,  taking  care  to  avoid  the  reducing  flame.  (It  is  better 
to  place  the  Gooch  crucible  inside  a  platinum  crucible  during  the 
ignition.)  Cool  in  a  desiccator  and  weigh.  Calculate  the  normal 
lead  number  from  the  following  formula  : 


In  the  above  formula  P  =  normal  lead  number  (grams  of 
metallic  Pb  in  the  precipitate  from  100  cc.  of  the  sample);  S  = 
grams  of  PbS(>4  corresponding  to  25  cc.  of  the  standard  lead 
acetate  solution  as  determined  in  a  blank  analysis  made  on  water 
containing  4-5  drops  of  glacial  acetic  acid;  and  W  =  grams  of 
PbSC>4  in  10  cc.  of  the  filtrate  from  the  lead  acetate  precipitate  as 
just  described. 

Residual  Color  in  Filtrate  after  Precipitation  with  Lead  Acetate. 
—  Determine  the  color  value  in  terms  of  red  and  yellow  of  a  por- 
tion of  the  filtrate  from  the  lead  acetate  precipitate  obtained  in 
the  determination  of  vanillin  and  coumarin,  using  a  1-inch  Lovi- 
bond  cell.  Multiply  the  reading  by  2,  thus  reducing  the  results 
to  the  basis  of  the  original  extract.  In  case  the  actual  read- 
ing of  the  solution  is  greater  than  5  red  and  15  yellow,  as  may 
happen  if  the  extract  is  highly  colored  with  caramel,  use  the  0.5 
or  0.25  inch  cell  and  multiply  the  readings  by  4  or  by  8,  respect- 
ively. 

Divide  the  figures  for  red  and  yellow,  respectively,  by  the  cor- 
responding figures  obtained  by  measurement  of  the  original 
extract  and  multiply  the  quotients  by  100,  thus  obtaining  the  per- 
centages of  the  two  colors  remaining  in  the  lead  acetate  filtrate. 

Calculate  also  the  ratio  of  red  to  yellow  in  both  extract  and 
lead  filtrate. 

NOTE.  —  Determine  the  color  value  of  the  original  extract  as  follows: 
Pipette  2  cc.  into  a  50  cc.  graduated  flask  and  make  up  to  the  mark  with  a 
mixture  of  equal  parts  95%  alcohol  by  volume  and  water.  Determine  the 
color  value  of  this  diluted  extract  in  terms  of  red  and  yellow  by  means  of  the 


ANALYSIS  OF  FOODSTUFFS  471 

Lovibond  tintometer,  using  the  1-inch  cell.  To  obtain  the  color  value  of  the 
original  extract  multiply  the  figures  for  each  color  by  25. 

Per  Cent  of  Color  Insoluble  in  Amyl  Alcohol  (Marsh  Test). — 

Pipette  25  cc.  of  the  extract  into  a  porcelain  dish  and  Qvaporate 
just  to  dryness  on  the  steam  bath.  Transfer  to  a  50  cc.  flask  by 
means  of  95%  alcohol  by  volume  and  water,  using  a  total  of 
26.3  cc.  of  95%  alcohol.  Dilute  to  the  mark  with  water.  Trans- 
fer 25  cc.  of  this  solution  to  a  separatory  funnel.  Add  25  cc.  of 
the  Marsh  reagent  and  shake  lightly  to  avoid  emulsification.  Let 
the  layers  separate  and  repeat  the  shaking  and  standing  twice 
again.  After  the  layers  have  separated  clearly,  run  off  the  lower 
aqueous  layer  into  a  25  cc.  cylinder  and  make  up  the  volume  with 
50%  (by  volume)  alcohol.  Compare  in  a  colorimeter  with  the 
remaining  25  cc.  portion  which  has  not  been  extracted  and  express 
the  results  as  percentage  of  color  insoluble  in  amyl  alcohol. 

Marsh  Reagent. — Mix  100  cc.  of  amyl  alcohol,  3  cc.  of  sirupy 
phosphoric  acid  and  3  cc.  of  water.  Shake  immediately  before 
using.  If  the  reagent  becomes  colored  on  standing,  the  amyl 
alcohol  should  be  redistilled  over  5%  phosphoric  acid. 

Total  Solids. — Determine  the  total  solids  on  10  grams  of  the 
sample  by  evaporating  in  a  dish  containing  a  weighed  amount  of 
quartz  sand  as  described  on  page  410. 

Ash. — Evaporate  10  grams  of  the  extract,  char  and  ignite 
until  free  of  carbon  at  the  lowest  possible  heat,  not  exceeding  dull 
redness. 

Sucrose. — Place  200  cc.  of  the  extract  in  a  porcelain  dish, 
exactly  neutralize  to  litmus  paper  with  approximately  N  NaOH 
and  evaporate  to  about  a  quarter  of  the  original  volume.  Trans- 
fer to  a  200  cc.  volumetric  flask,  add  sufficient  normal  lead  acetate 
to  clarify  and  dilute  to  the  mark  with  water.  If  necessary,  add 
also  1-2  cc.  of  alumina  cream  before  dilution.  Shake  and  filter 
through  a  folded  filter.  Polarize  the  filtrate  at  20°  C.  in  a  200  mm. 
tube.  Free  about  half  of  this  filtrate  from  Pb  by  treating  with 
dry  K2C2O4  added  a  little  at  a  time.  Shake  after  each  addition 
and  avoid  an  excess.  Filter  through  a  dry  paper,  pipette  50  cc. 
of  the  lead-free  filtrate  into  a  100  cc.  volumetric  flask  and  add  25 
cc.  of  water.  Then  add  little  by  little,  while  rotating  the  flask, 
5  cc.  of  cone.  HC1.  Heat  the  flask,  after  mixing,  in  a  water  bath 
at  70°  C.  The  temperature  of  the  solution  in  the  flask  should 


472  TECHNICAL  METHODS  OF  ANALYSIS 

reach  67-69°  C.  in  two  and  one-half  to  three  minutes.  Maintain  a 
temperature  of  approximately  69°  C.  during  seven  to  seven  and 
one-half  minutes,  making  the  total  time  of  heating  ten  minutes. 
Remove  the  flask,  cool  the  contents  rapidly  to  20°  C.,  and  dilute 
to  100  cc.  Polarize  this  solution  at  20°  C.,  and  multiply  the 
invert  reading  by  2  to  correct  for  dilution.  (If  it  is  necessary  to 
polarize  at  a  temperature  other  than  20°  C.,  both  direct  and  invert 
polarizations  and  dilution  to  volume  should  be  made  at  exactly 
the  same  temperature.)  Calculate  the  sucrose  by  the  following 
formula : 

_     100  (A  -B]  26 

/\ 


T 
142.66-4; 

2 

where  S  =  per  cent  of  sucrose; 

A  —  direct  reading; 

B  =  invert  reading; 
and        T= temperature  at  which  readings  are  made. 

NOTE. — In  calculatL-g  the  percentage  of  sucrose,  the  relation  of  the 
amount  of  sample  to  the  normal  weight  (26.048  grams  per  100  cc.)  must  be 
taken  into  consideration.  This  is  corrected  for  in  the  above  formula  by  the 
second  fraction. 

Vanilla  Resins  (Qualitative  Tests). — Evaporate  50  cc.  of  the 
extract  in  a  glass  dish  on  a  water  bath  until  the  alcohol  is  removed 
and  make  up  to  about  the  original  volume  with  hot  water.  If 
alkali  has  not  been  used  in  the  manufacture,  the  resins  will  appear 
as  a  flocculent  red  to  brown  residue.  Acidify  with  acetic  acid, 
let  stand  a  short  time,  collect  the  resins  on  a  filter,  wash  with 
water  and  reserve  the  filtrate  for  further  tests. 

Place  a  portion  of  the  filter  with  the  attached  resins  in  a  few  cc. 
of  dil.  KOH  solution.  The  resins  are  dissolved,  giving  a  deep 
red  solution.  Acidify  and  the  resins  are  reprecipitated. 

Dissolve  a  portion  of  the  resins  in  alcohol.  To  one  fraction 
add  a  few  drops  of  FeCls  solution;  no  striking  coloration  should 
be  produced.  To  another  portion  add  HC1 ;  little  change  in  color 
should  result. 

To  a  portion  of  the  filtrate  obtained  above,  add  a  few  drops 
of  lead  subacetate  solution.  A  very  bulky  precipitate  should 


ANALYSIS  OF  FOODSTUFFS  473 

result  and  the  filtrate  from  this  precipitate  should  be  practically 
colorless. 

Test  another  portion  of  the  filtrate  from  the  resin  for  tannin 
with  a  solution  of  gelatin.  Tannin  should  be  present  in  varying 
but  small  quantities  and  should  not  be  present  in  great  excess. 

Glycerol. — Heat  to  boiling  in  a  flask  100  cc.*  of  the  extract  and 
treat  with  successive  small  portions  of  milk  of  lime  (containing 
about  15%  of  CaO)  until  it  becomes  first  darker  and  then  lighter 
in  color.  When  cool  add  200  cc.  of  95%  alcohol,  let  the  precipitate 
subside,  filter,  and  wash  with  95%  alcohol.  Evaporate  the  fil- 
trate in  a  porcelain  dish  on  the  water  bath  to  about  10  cc.  and 
proceed  as  in  the  determination  of  Glycerol  in  Lemon  Extract, 
page  459. 

NOTES. — (1)  This  method  embodies  the  tentative  and  official  methods  and 
recommendations  of  the  Association  of  Official  Agricultural  Chemists. 

(2)  The  limits  of  composition  of  pure  standard  vanilla  extracts  as  set 
forth  in  Bureau  of  Chemistry  Bulletin  163,  page  89  are  as  follows: 

(a)  Percentage  of  vanillin  should  be  not  less  than  0.10  nor  more  than  0.35. 

(6)  Normal  lead  number  should  be  not  less  than  0.40  nor  more  than  0.80. 

(c)  The  percentage  of  color  insoluble  in  acidified  amyl  alcohol  (Marsh's 
reagent)  should  be  not  more  than  35  and  will  seldom  exceed  25%. 

*  The  amount  of  glycerol  in  the  sample  taken  for  analysis  should  be  be- 
tween 0.10  and  0.40  gram. 


CHAPTER  XI 
MISCELLANEOUS  ANALYSES 

LEATHER 

Preparation  of  Sample. — Reduce  the  sample  for  analysis  to  as 
fine  a  state  of  division  as  practicable,  either  by  cutting  or  grinding. 

Moisture. — Dry  10  grams  for  sixteen  hours  between  95°  and 
100°  C.  Cool  in  a  desiccator  and  keep  the  dish  or  weighing  bottle 
tightly  covered  while  weighing.  Report  the  loss  in  weight  as 
moisture. 

Fat  and  Oil. — Extract  completely  5-10  grams  of  the  air-dry 
sample  in  a  Soxhlet  apparatus  with  petroleum  ether*  boiling  below 
80°  C.  Evaporate  off  the  ether  and  dry  the  extract  to  approx- 
imately constant  weight. 

Or,  if  preferred,  extract  30  grams  of  leather  as  described  above. 
In  the  latter  case,  the  extracted  leather,  when  freed  of  solvent, 
may  be  used  for  the  determination  of  water-soluble  material. 

Ash. — Incinerate  10-15  grams  in  a  tared  dish  at  a  dull  red  heat 
until  carbon  is  consumed.  If  it  is  d  fficult  to  burn  off  all  the  car- 
bon, treat  the  ash  with  hot  water,  filter  through  an  ashless  filter 
and  ignite  the  filter  and  residue  in  the  dish.  Then  add  the 
filtrate,  evaporate  to  dryness  and  ignite.  Cool  in  a  desiccator 
and  weigh  the  mineral  matter. 

Water-soluble  Matter. — Digest  30  grams  of  fat-free  leather 
with  water  in  a  percolator  overnight,  then  extract  with  water  at 
50°  C.  for  three  hours,  using  successive  small  portions.  The  total 
volume  of  solution  should  be  2  liters.  Pipette  out  100  cc.  into  a 
weighed  flat-bottom  dish  of  a  diameter  of  2.75-3  inches.  Evapo- 
rate to  dryness  and  dry  to  constant  weight  at  100-105°  C.  From 
this  weight  calculate  the  per  cent  of  water-soluble  material. 

*  The  extraction  will  require  8-12  hours,  depending  upon  the  amount  of 
fat.  If  convenient,  let  the  extraction  run  overnight.  Place  a  layer  of  fat- 
free  cotton  above  and  below  the  ground  leather  in  the  extractor. 

474 


MISCELLANEOUS  ANALYSES  475 

Glucose. — Place  200  cc.  of  the  water  extract  prepared  above 
in  a  500  cc.  flask,  add  25  cc.  of  a  saturated  solution  of  normal  lead 
acetate ;  shake  frequently  five  to  ten  minutes,  and  filter  through  a 
dry  filter.  Keep  funnels  and  beakers  covered  to  prevent  evapo- 
ration. Add  to  the  filtrate  an  excess  of  solid  K2C2O4.  Mix 
frequently  for  fifteen  minutes  and  filter,  returning  the  filtrate 
until  it  runs  through  clear.  Pipette  150  cc.  of  this  clear  filtrate 
into  a  500  cc.  Erlenmeyer  flask.  Add  5  cc.  of  cone.  HC1  and  boil 
under  a  reflux  condenser  for  two  hours.  Cool,  add  a  small  piece  of 
litmus  paper  and  neutralize  with  anhydrous  Na2CO3.  Transfer 
to  a  200  cc.  graduated  flask  and  dilute  to  volume.  Filter  through  a 
dry  double  filter,  rejecting  the  first  filtrate.  The  final  filtrate 
must  be  clear.  Determine  the  dextrose  immediately  in  50  cc.  of 
this  solution,  using  the  Munson  and  Walker  method  as  described 
under  Total  Reducing  Sugars  on  page  403.  Calculate  the  results 
to  the  original  leather  and  report  as  "  glucose,  calculated  as 
dextrose." 

In  making  the  determination  place  25  cc.  of  the  CiiSO4  solution 
and  25  cc.  of  the  alkaline  tartrate  solution  in  a  400  cc.  beaker. 
Add  50  cc.  of  the  prepared  leather  solution,  heat  to  boiling  in 
exactly  four  minutes,  and  boil  for  two  minutes.  The  burner 
should  be  adjusted  by  a  preliminary  trial  so  that  these  conditions 
are  fulfilled.  Filter  immediately  without  diluting  through  a 
weighed  Gooch  crucible  containing  an  asbestos  mat.  Wash  thor- 
oughly with  hot  water,  then  with  alcohol,  and  finally  with  ether. 
Dry  for  one-half  hour  at  the  temperature  of  boiling  water  and 
weigh  as  Cu2O. 

NOTE. — If  the  above  conditions  of  dilution,  etc.,  are  all  fulfilled,  50  cc.  of 
the  clarified  and  neutralized  solution  will  correspond  to  0.5  gram  of  the  orig- 
inal leather  (assuming  exactly  30  grams  taken  for  the  water-soluble  deter- 
mination) . 

Nitrogen. — Determine  N  on  0.7  gram  of  leather  by  the  Gun- 
ning modification  of  the  Kjeldahl  method  as  described  on  page  65. 
Multiply  the  nitrogen  by  5.62  to  obtain  the  amount  of  "  hide 
substance." 

Chromium  in  Chrome  Leather. — For  this  determination  see 
page  478. 

Free  Mineral  Acid. — Most  leathers  when  moistened  are  acid 
to  litmus  but  this,  unless  extremely  marked,  is  no  evidence  of  free. 


476  TECHNICAL  METHODS  OF  ANALYSIS 

mineral  acid.  A  marked  acid  reaction,  however,  especially  in 
the  presence  of  much  sulfate,  is  suspicious.  On  the  other  hand, 
even  if  the  leather  contains  free  H2S04,  the  ash  will  usually  be 
alkaline,  since  acid  is  driven  off  on  ignition  and  a  portion  of  the 
sulfates  is  reduced  to  sulfides,  and  even  to  carbonates  or  free  bases, 
especially  in  the  case  of  lime  salts.  There  is  no  method  which 
will  give  with  certainty  a  true  figure  for  free  H2S04.  The  two 
methods  which  are  probably  the  best  are  described  below: 

(1)  JEAN  METHOD. — Dry  10  grams  or  more  of  finely  divided 
leather  at  not  over  95°  C.  (drying  in  a  vacuum  desiccator  is  prefer- 
able) and  extract  with  absolute  alcohol  in  a  Soxhlet  extractor, 
placing  about  0.5  gram  of  Na^COs  powder  in  the  flask  to  combine 
with  any  acid  dissolved  by  the  alcohol.     Extract  until  the  alcohol 
comes  over  colorless.     Distill  off  the  alcohol,  transfer  to  a  platinum 
dish  and  ignite  to  a  char.     Leach  out  with  hot  water,   filter,   and 
determine  the  total  SOs  in  the  solution  by  acidifying  first  with 
HC1  and  then  adding  to  the  boiling  solution  an  excess  of  BaC^ 
solution.     Filter  and  weigh  the  BaSO4  in  the  usual  way.     Calcu- 
late to  H2SO4. 

CALCULATION.— BaSO4  X  0.4202  =  H2SO4. 

NOTE. — The  alcohol  used  must  be  absolute  and  freshly  prepared  by 
distilling  from  quick-lime.  The  method  is  based  on  the  fact  that  H^SCX  is 
soluble  in  absolute  alcohol,  but  sulfates  are  not.  For  this  reason  also  the 
leather  must  be  dried,  but  extreme  drying,  and  especially  the  use  of  a  high 
temperature,  must  be  avoided,  as  this  will  cause  the  acid  to  attack  and  com- 
bine with  organic  constituents  of  the  leather. 

If  the  above  conditions  are  complied  with,  a  positive  result  may  be  taken 
as  proof  of  the  presence  of  free  acid;  but  a  negative  result  is  not  conclusive 
evidence  that  acid  is  not  present,  even  in  injurious  quantities,  since  it  has  been 
proved  that  even  a  long  extraction  may  fail  to  remove  all  the  acid  from  the 
leather. 

(2)  PROCTOR  AND  SEARLE  METHOD. — Moisten  2-3  grams  of 
leather  in  a  platinum  dish  with  exactly  25  cc.  of  accurately  stand- 
ardized 0.1  N  Na2COs  solution;  evaporate  to  dryness  and  char  at  a 
gentle  heat  until  thoroughly  carbonized.   This  drives  off  practically 
all  organic  sulfur,  while  the  reduction  of  sulfates  is  very  slight.  Pul- 
verize the  carbonaceous  mass  with  a  glass  rod  and  leach  with  boiling 
water,  filtering  through  a  small  quantitative  filter  paper.     Dry 
the  filter  paper  and  return  it  to  the  mass  in  the  dish,  and  ignite 
the  whole  until  all  or  nearly  all  carbon  has  disappeared.     Cool 


MISCELLANEOUS  ANALYSES  477 

and  treat  the  ash  with  25  cc.  of  0.1  N  HC1,  accurately  standard- 
ized against  the  0.1  N  Na2COs.  Wash  the  whole  into  the  beaker 
containing  the  filtrate  of  the  charred  mass  and  add  methyl  orange. 
If  the  liquid  now  shows  an  acid  reaction,  titrate  with  0.1  N  alkali 
and  calculate  the  titration  to  KkSCU  (unless  it  is  known  that  the 
acid  is  HC1).  If  the  reaction  is  alkaline,  H^SCU  is  absent,  and  no 
notice  need  be  taken  of  the  alkalinity. 

NOTE. — The  two  above  methods  for  free  acid  are  chiafly  of  value  in  com- 
paring different  leathers,  although  if  carefully  carried  out  they  give  results 
which  are  reasonably  accurate.  Probably  the  most  accurate  method  at  pres- 
ent known  is  that  of  Wuensch,  but  it  is  a  troublesome  and  time-consuming 
procedure.  It  is  described  in  H.  R.  Proctor:  "  Leather  Industries  Laboratory 
Book  of  Analytical  and  Experimental  Methods/'  1908  edition,  page  371. 

REFERENCE. — The  above  procedures,  with  the  exception  of  those  for  free 
mineral  acid,  are  essentially  the  methods  of  the  American  Leather  Chemists' 
Association. 


CHROMIUM  IN  CHROME  SALTS  AND  LEATHERS 

General. — The  most  accurate  method  for  the  determination  of 
chromium  in  chrome  salts  is  to  oxidize  to  the  chromate  condition 
and  then  determine  the  latter  either  gravimetrically,  by  precip- 
itation as  PbCrC>4,  or  volumetrically. 

Chrome  Liquors  (Chrome  Tanning  Liquors,  Chromium  Ace- 
tate, etc.). — (a)  ONE  BATH  CHROME  LIQUORS  (USED  IN  TAN- 
NING).*— Dilute  a  weighed  quantity  of  the  liquor  with  water 
to  a  definite  volume,  so  that  the  dilution  contains  from  0.15  to 
0.25%  of  Cr2O3.  Pipette  10  cc.  of  this  solution  into  a  300  cc. 
Erlenmeyer  flask  and  add  about  50  cc.  of  water  and  2  grams  of 
Na2(>2.  Boil  gently  one-half  hour,  adding  water  if  necessary  to 
keep  the  volume  from  falling  below  about  15  cc.  Cool,  neutralize 
with  cone.  HC1  and  add  5  cc.  excess.  Again  cool  and  add  10  cc. 
of  10%  KI  solution.  After  one  minute  run  in  from  a  burette  0.1 
N  thiosulfate  until  the  iodine  color  nearly  disappears,  then  add  a 
few  cc.  of  starch  solution  and  titrate  to  the  disappearance  of  the 
blue.  Calculate  to  C^Os. 

CALCULATION.— 1  cc.  of  0.1  N  thiosulfate  =  0.002533  gram 
Cr2O3. 

*  J.  Am.  Leather  Chem.  Assoc.  14,  page  667  (1919). 


478  TECHNICAL  METHODS  OF  ANALYSIS 

(6)  CHROMIUM  ACETATE  SOLUTIONS  (USED  IN  MORDANTING). — 

Weigh  out  about  10  cc.  accurately  and  dilute  to  100  cc.  in  a 
volumetric  flask.  Mix  thoroughly  and  pipette  10  cc.  into  a 
300  cc.  Erlenmeyer  flask.  Then  proceed  as  above. 

(c)  ALTERNATIVE  METHOD. — If  the  material  is  free  from  sul- 
f  ates,  the  C^Oa  may  be  determined  gravimetrically  as  follows  : 

Oxidize  with  peroxide  as  above.  Filter  out  any  insoluble 
matter.  Heat  nearly  but  not  quite  to  boiling.  Make  acid  with 
acetic  acid  and  add  an  excess  of  lead  acetate  solution  containing  a 
few  drops  of  acetic  acid.  Let  stand  on  the  steam  bath  until  clear, 
but  avoid  long  standing  on  account  of  the  danger  of  forming  basic 
compounds.  Filter  through  a  weighed  Gooch  crucible,  wash  with 
hot  water,  and  dry  at  105°  C.  Set  the  Gooch  crucible  inside  of  a 
larger  platinum  crucible,  ignite  to  very  dull  redness,  cool  and 
weigh  as  PbCrCU.  Calculate  to  C^Os. 

CALCULATION.— PbCrO4  X  0.2352  =  Cr2O3. 

NOTE. — In  the  case  of  chrome  liquors  containing  impurities  such  as 
organic  matter,  dyestuffs,  etc.,  oxidation  cannot  be  effected  with  peroxide 
alone.  The  solution  must  be  rendered  alkaline  with  NaOH  and  boiled  with 
cone.  KMnO4  solution.  The  violet  color  of  the  permanganate  disappears  on 
boiling  and  more  permanganate  must  be  added  and  the  solution  again  boiled. 
Repeat  this  process  until  a  violet  red  color  finally  persists  even  after  boiling 
and  then  remove  the  small  excess  of  KMnO4  by  warming  the  solution  with  2 
drops  of  alcohol.  Filter  and  wash  and  determine  the  CraOs  in  the  filtrate. 

Chromium  in  Chrome  Leather.* — Ash  3  grams  of  leather.  Mix 
the  ash  thoroughly  with  4  grams  of  a  mixture  of  equal  parts  of 
Na2COs,  K2COs  and  powdered  borax  glass  and  fuse  in  a  platinum 
crucible  for  thirty  minutes.  Dissolve  the  cooled  fusion  in  hot 
water  and  slightly  acidify  with  HC1.  Filter.  If  there  is  any 
residue  on  the  filter,  ash  it  and  treat  the  ash  with  1  gram  of  the 
above  fusion  mixture  in  the  same  manner  as  the  original  ash, 
adding  the  solution  to  the  first.  Make  up  to  500  cc.,  and  pipette 
out  100  cc.  of  this  solution  into  an  Erlenmeyer  flask.  Neutralize 
with  cone.  HC1,  add  5  cc.  in  excess  and  then  add  10  cc.  of  10% 
KI  solution  and  titrate  as  previously  described. 

*  J,  Am.  Leather  Chem.  Assoc.  14,  page  668  (1919). 


MISCELLANEOUS  ANALYSES  479 


SUMAC  EXTRACT 

Solutions  Required. — (1)  Potassium  Permanganate:  0.50  gram 
pure  KMnO^  per  liter. 

(2)  Indigo  Carmine:  5  grams  pure  indigo  carmine  and  50  grams 
cone.  H2S04  per  liter. 

(3)  Gelatin:  20  grams  pure  gelatin  per  liter. 

(4)  Acid  Salt  Solution:  a  saturated  solution  of  NaCl  containing 
50  cc.  of  cone.  H2S04  per  liter. 

STANDARDIZATION. — The  indigo  carmine  solution  must  be  fil- 
tered and  should  give  a  pure  yellow,  free  from  any  trace  of  brown, 
when  oxidized  with  KMnO4.  Dilute  25  cc.  of  this  solution  in  a  large 
white  porcelain  dish  with  about  750  cc.  of  tap  water  and  add  the 
KMnC>4,  drop  by  drop,  from  a  burette  until  a  pure  yellow  is 
obtained,  stirring  the  liquid  constantly.  The  dropping  should  be  as 
nearly  as  possible  at  a  similar  rate  for  each  experiment  and  should 
be  slower  toward  the  end  of  the  titration.  The  final  end-point  must 
be  approached  cautiously  by  adding  the  KMnCX  very  slowly 
until  the  pure  yellow  liquid  shows  a  faint  pinkish  rim,  which  can 
most  clearly  be  seen  on  the  shaded  side.  At  least  two  titrations 
should  be  made. 

Total  Astringency. — Weigh  out  2.5-3.5  grams  of  the  sumac 
extract  and  dilute  to  500  cc.  Place  5  cc.  of  this  solution  in  a  large 
porcelain  dish  with  25  cc.  of  the  indigo  carmine  solution  and 
750  cc.  of  tap  water.  Titrate  with  the  KMnC>4  solution  as  above 
described,  running  at  least  two  determinations.  Subtract  from 
this  titration  the  amount  of  KMnO4  required  by  the  indigo  solu- 
tion in  standardizing,  and  from  the  known  strength  of  the  KMnC>4 
solution  calculate  the  number  of  cc.  of  0.1  N  KMnC>4  reduced  by 
the  total  astringency.  From  this  calculate  the  total  astringency 
as  tannins. 

CALCULATION. — 1  cc.  of  0.1  N  KMnO4  =  0.004 157  gram  tannin. 

Astringent  Non-tannins. — To  50  cc.  of  the  dilute  sumac 
solution  above  referred  to  add  25  cc.  of  the  gelatin  solution, 
25  cc.  of  the  acid  salt  solution  and  10  grams  of  china  clay  or 
kaolin.  Shake  thoroughly  for  about  five  minutes  and  filter 
through  a  dry  filter.  This  removes  the  tannins.  Titrate  10  cc. 
of  the  filtrate  (corresponding  to  5  cc.  of  the  original  sumac  extract 
solution)  for  non-tannins  in  exactly  the  same  manner  as  the  total 


480  TECHNICAL  METHODS  OF  ANALYSTS 

astringency  was  determined,  and  calculate  the  per  cent  of  non- 
tannins  by  means  of  the  same  factor. 

Tannin. — Subtract  the  percentage  of  non-tannins  from  the 
percentage  of  total  astringency  and  report  the  difference  as  the 
percentage  of  tannin  in  the  extract. 

REFERENCES. — H.  R.  Proctor:  "  Leather  Industries  Laboratory  Book  of 
Analytical  and  Experimental  Methods,"  2d  Ed.,  page  227.  Leach:  "  Food 
Inspection  and  Analysis,"  page  282. 

20  PER  CENT  PARA  RUBBER  COMPOUND 

General. — This  method  is  the  procedure  recommended  by 
the  Underwriters'  Laboratories  for  Code  Rubber  and  should  be 
used  for  all  rubber  insulation  on  wires  and  cables  other  than  30% 
Para  Compound.  All  determinations  should  be  performed  in 
duplicate  and  must  check  within  0.2%,. calculated  on  the  total 
sample.  The  average  value  should  be  taken  as  the  true  value. 

Preparation  of  Sample. — Take  a  sufficient  length  of  wire  to 
give  at  least  15  grams  of  rubber  compound.  Remove  the  outer 
coverings  and  sandpaper  the  surface  of  the  rubber  sufficiently 
to  remove  all  irregularities,  and  in  any  case  to  a  depth  of  not  less 
than  0.003  inch.  (This  is  to  get  rid  of  extraneous  matter  absorbed 
from  the  impregnating  compound.)  .  Wipe  with  a  dry  cloth. 

In  some  cases  after  the  mechanical  cleaning  it  may  be  neces< 
sary  to  clean  further  with  a  cloth  dampened  with  ether,  taking 
care  to  avoid  allowing  the  ether  to  penetrate  the  compound  to 
any  marked  extent.  Strip  all  the  rubber  from  the  wire  and  cut 
into  small  pieces.  Grind  this  entire  sample  in  a  mill  until  it  is 
finely  divided,  avoiding  heating.  Spread  the  sample  out  on  a 
piece  of  glazed  paper,  pass  over  it  a  strong  magnet  to  remove  any 
metal  which  may  have  come  from  the  grinder,  and  then  mix 
thoroughly. 

Acetone  Extract. — Extract  a  2-gram  sample  with  c.  P. 
acetone  until  the  sample  is  practically  free  from  matter  soluble  in 
acetone  (not  less  than  five  hours),  the  speed  of  condensation  being 
such  that  at  least  150  drops  per  minute  fall  directly  upon  the 
sample.  Distill  off  the  acetone,  dry  the  flask  with  the  extract  to 
constant  weight  at  95-100°  C.,  and  weigh. 

Extraction  Apparatus. — A  very  satisfactory  extractor  is  that 
recommended  by  the  Joint  Rubber  Insulation  Committee  and 


MISCELLANEOUS  ANALYSES 


481 


shown  in  Fig.  25,  but  any  extractor  may  be  used  which  conforms 
to  the  following  specifications: 

1.  The  extraction  cup  shall  be  surrounded  by  the  vapor  of 
the  solvent  at  its  boiling  point. 

2.  The  condensed  solvent  shall  fall  directly  on  the  sample. 


Block  tin  tubing,  8  mm. 
outside  diameter 


All  dimensions  in  millimeters 


FIG.  25. — Extraction  Apparatus  for  Rubber. 

3.  The  outlet  from  the  extraction  cup  shall  be  at  the  bottom 
only. 

4.  No  rubber  or  cork  stoppers  shall  come  in  contact  with  the 
solvent. 

5.  The  sample  shall  be  put  directly  into  the  extraction  cup 
without  the  use  of  a  paper  thimble,  a  disk  of  filter  paper  or  its 


482  TECHNICAL   METHODS  OF  ANALYSIS 

equivalent  at  the  bottom  of  the  cup  being  depended  upon  to  hold 
back  the  solid  particles. 

Chloroform  Extract. — Without  drying  the  residue  from  the 
acetone  extraction,  extract  with  CHCls  for  three  hours.  If  at  this 
time  the  solution  is  not  coming  through  colorless,  continue  until 
it  is  colorless,  provided  the  total  extraction  does  not  exceed  five 
hours.  Distill  off  the  CHCla,  dry  the  flask  with  the  extract  to 
constant  weight  at  95-100°  C.,  and  weigh. 

Alcoholic  Potash  Extract. — Prepare  a  normal  alcoholic 
KOH  solution  *  by  dissolving  c.  P.  KOH  in  95%  alcohol  which 
has  been  freshly  distilled  over  KOH.  Let  the  solution  stand 
overnight  and  filter. 

Dry  the  residue  from  the  CHCk  extraction  at  50-60°  C., 
place  in  a  200  cc.  Erlenmeyer  flask  and  boil  with  a  reflux  con- 
denser for  four  hours  with  50  cc.  of  normal  alcoholic  KOH.  Filter 
the  solution  into  a  beaker;  wash  first  with  100  cc.  of  absolute 
alcohol,  then  with  50  cc.  of  hot  water,  and  evaporate  to  approximate 
dryness.  Add  a  little  water,  transfer  into  a  separatory  funnel, 
dilute  to  100  cc.  and  acidify  with  dil.  HC1.  Shake  out  with  20 
cc.  portions  of  ether  until  the  last  portion  is  colorless,  after  which 
shake  out  twice  more.  Shake  out  the  ether  solution  twice  with 
50  cc.  of  water.  Filter  the  ether  solution  into  a  small  weighed 
beaker  and  wash  the  filter  with  a  little  ether;  evaporate  off  the 
ether  without  boiling,  dry  to  constant  weight  at  95-100°  C.,  and 
weigh.  • 

Total  Sulfur. — Mix  a  0.5  gram  of  sample  with  4  grams  of 
Na202  (sulfur  free)  and  6  grams  of  ^COs  in  a  dry  15  cc.  iron 
crucible;  cover  the  crucible,  insert  into  a  close-fitting  hole  in  an 
asbestos  board  and  place  about  10  cm.  above  a  flame  turned  very 
low.  Gradually  increase  the  flame  until  the  mixture  fuses,  pro- 
ceeding cautiously,  as  rapid  heating  will  cause  an  explosion,  and 
then  apply  the  full  heat  for  fifteen  to  twenty  minutes.  Rotate 
the  crucible  while  the  melt  solidifies.  When  cool  put  the  cru- 
cible and  cover  into  a  200  cc.  casserole  filled  with  water,  add 
5-10  cc.  of  bromine  water,  and  boil  until  the  melt  is  dissolved  and 
the  bromine  expelled.  Let  the  precipitate  settle,  with  the  addi- 
tion of  MgO  if  necessary;  decant  the  liquid  through  a  thick  filter 
and  wash  the  residue  by  decantation  with  hot  water  until  prac- 
*  56.1  grams  of  KOH  per  liter. 


MISCELLANEOUS  ANALYSES  483 

tically  neutral.  Acidify  the  filtrate  with  HC1,  evaporate  to  dry- 
ness  and  dehydrate  the  silica;  take  up  in  400  cc.  of  water,  add  5  cc. 
of  dil.  HC1  and  filter.  Bring  to  a  boil  and  add  slowly  a  slight 
excess  of  hot  10%  BaCl2  solution.  Let  stand  overnight,  filter, 
wash,  ignite  and  weigh  the  BaSC>4.  Calculate  to  S. . 

CALCULATION.— BaS04  X  0. 1373  =  S. 

NOTE. — In  case  of  disagreement  on  total  sulfur,  the  Carius'  Method  shall 
be  used.  (See  Gattermann:  "Practical  Methods  of  Organic  Chemistry." 

Sulfur  (Alternative  Method). — Fuse  a  0.5  gram  sample  with  a 
mixture  of  2  parts  by  weight  of  KNOs,  3  parts  of  Na2COs  and  1  part 
of  K2COs  in  a  porcelain  crucible.  The  heating  should  at  the  start 
be  conducted  at  a  very  low  temperature.  After  fusion,  disin- 
tegrate the  melt  with  water.  Filter,  boil  with  bromine  water,  and 
acidify  with  excess  of  HC1.  Boil  down  in  order  to  break  up  nitrates, 
dilute  to  at  least  300  cc.  with  water  and  finally  precipitate  while 
hot  with  an  excess  of  BaCb  solution.  Let  stand  overnight,  filter 
and  wash,  ignite  and  weigh  the  BaSC>4. 

Ash. — Place  in  a  small  porcelain  dish  a  weight  of  acetone 
extracted  compound  which,  before  such  extraction,  had  a  weight 
of  1  gram.  Burn  off  the  rubber  completely  at  as  low  a  tempera- 
ture as  possible,  without  letting  it  catch  fire.  (High  temperatures 
must  be  carefully  avoided.)  This  may  be  done  in  either  of  two 
ways:  First,  by  inserting  the  dish  into  a  close-fitting  hole  in  an 
asbestos  board  and  heating  carefully  over  a  small  flame,  the  dish 
afterwards  being  placed  on  a  triangle  and  just  sufficient  flame 
applied  to  the  sides  to  remove  any  condensation;  or,  second,  by 
placing  the  dish  containing  the  sample  near  the  mouth  of  a  suitably 
heated  muffle  furnace.  Cool  in  a  desiccator  and  weigh  the  ash. 

Free  Sulfur. — The  free  S  will  be  in  the  acetone  extract.  Add  to 
the  flask  containing  the  acetone  extract  10-15  cc.  of  fuming  HNOs. 
Place  the  flask  on  the  water  bath  until  all  is  in  solution.  Transfer 
to  a  hot  plate  and  add  small  portions  of  KClOa,  until  the  solution 
is  decolorized.  Evaporate  to  dryness,  carefully  avoiding  any 
SOs  fumes  which  would  foe  absorbed  by  the  solution.  Take  up  the 
residue  with  50  cc.  of  water,  add  3  cc.  of  cone.  HC1  and  filter 
into  a  600  cc.  beaker.  Dilute  to  about  400  cc.,  heat  to  boiling  and 
precipitate  with  BaCl2  in  the  usual  manner.  Let  stand  over- 
night, protected  from  SO3  fumes.  Filter  off  the  BaSO4.  Ignite, 
cool  in  a  desiccator  and  weigh.  Calculate  to  S.  Subtract  from 


484  TECHNICAL  METHODS  OF  ANALYSIS 

this  result  any  S  found  in  a  "  blank  "  which  should  be  carried 
through  simultaneously. 

NOTE. — The  procedure  for  free  sulfur  is  not  included  in  the  Under- 
writers' methods. 

CASE-HARDENING  COMPOUNDS 

General. — For  case-hardening  steel  a  great  variety  of  sub- 
stances is  used.  Among  the  more  common  ones  are  materials 
containing  coke,  charcoal,  flour,  grain,  fibers,  BaCOa,  cyanides, 
Na2C03,  crushed  bone,  powdered  glass,  rosin,  gums,  etc.  The 
sample  should  first  be  examined  under  the  microscope  to  note  its 
general  appearance  and  to  detect  if  possible,  any  of  the  fore- 
going substances. 

The  following  is  an  attempt  at  a  general  scheme  of  analysis 
but  may  have  to  be  modified  to  suit  conditions. 

Ether  Extract. — Mix  the  sample  thoroughly  and  quarter  it 
down  to  about  50  grams.  Extract  10  grams  or  more  with  ether 
in  a  Soxhlet  extraction  thimble,  collecting  the  extract  in  a  weighed 
Soxhlet  flask.  Evaporate  off  the  ether  by  placing  the  flask  in 
warm  water,  dry  the  residue  at  100°  C.,  and  weigh.  If  the  extract 
is  appreciable  in  amount  it  should  be  tested  for  rosin  and  its  iden- 
tity ascertained,  if  possible,  by  determining  the  saponification 
number,  iodine  number,  refractive  index,  etc. 

Moisture. — Dry  2  grams  (using  the  extracted  material  if  the 
original  contains  oil)  at  100°  C.  until  the  weight  is  constant.  The 
loss  indicates  moisture. 

Volatile  Matter. — The  volatile  matter  is  determined  in  exactly 
the  same  manner  as  the  volatile  matter  in  the  Proximate  Analysis 
of  Coal  (page  173).  Grind  2  grams  of  the  material,  on  which  the 
moisture  has  been  determined,  rapidly  to  a  fine  powder  and  place 
1  gram  in  a  covered  platinum  crucible  over  a  Chaddock's  burner, 
gas  pressure  1.1  inches,  and  burn  for  exactly  seven  minutes.  Cool 
and  weigh.  The  loss  is  the  volatile  matter. 

Ash. — Ignite  2  grams  in  a  porcelain  crucible  until  the  ash  is 
free  from  carbonaceous  matter.  Dry  in  a  desiccator  and 
weigh. 

Loss  on  Heating  at  850°  C.  for  Six  Hours. — This  should  be 
done  in  a  porcelain  dish,  3  inches  in  diameter  and  2  inches  deep. 


MISCELLANEOUS  ANALYSES  485 

Weigh  the  dish  empty  and  then  fill  it  with  the  compound,  heaping 
it  up  and  packing  down.  Weigh  again  to  determine  the  amount 
of  substance  taken.  Place  in  a  muffle,  the  temperature  of  which 
has  been  ascertained  by  means  of  a  pyrometer,  and  heat  at  850°  C. 
for  six  hours.  Cool  in  a  desiccator  and  determine  the  loss  in 
weight. 

Analysis  of  Ash. — The  ash  should  be  analyzed  in  the  ordinary 
manner  for  Ba  (probably  present  as  carbonate  if  at  all),  CaO, 
P20s,  SO4,  Na  and  K.  It  should  be  noted  whether  the  ash  is 
alkaline  or  acid  and,  if  so,  the  extent  should  be  determined  by  titra- 
tion.  The  presence  or  absence  of  carbonates  should  also  be  noted. 
If  Caa(PO4)2  is  found,  the  material  probably  contains  ground  bone. 

Water  Extract. — Extract  10-20  grams  or  more  with  hot  water 
(after  extracting  with  ether  if  any  oil  is  present)  in  a  Soxhlet 
extractor,  collecting  the  extract  in  a  weighed  flask.  Evaporate 
off  the  water;  dry  at  100°  C.  and  weigh.  If  the  water  extract  is 
appreciable  it  should  be  analyzed.  The  best  .procedure  is  to 
make  it  up  to  a  given  volume  and  ascertain  its  nature  qualitatively 
and  then  make  quantitative  determinations  on  separate  aliquots. 
It  should  be  remembered  that  it  is  unnecessary  to  test  for  any- 
thing that  is  insoluble  in  water. 

Nitrogen. — (a)  TOTAL  NITROGEN. — This  is  determined  by  the 
Kjeldahl  method,  modified  to  include  nitrogen  present  as  nitrates, 
using  1-4  grams  of  the  material  (see  page  67). 

(b)  NITROGEN  AS  AMMONIA. — Place  1-5  grams  in   a  500  cc. 
round-bottom    flask.     Add    about   200   cc.    of   water  and   5-10 
grams   of   MgO,    free    from   carbonates.      Connect  with  a  con- 
denser and  distill  into  50  cc.  of  0.1  N  HC1.     Titrate  the  excess  of 
HC1  with  0.1  N  NaOH  and  calculate  the  difference  to  NH3. 

(c)  PROTEIN  NITROGEN  AND  NITRATES. — A  qualitative  test 
on  the  water  extract  will  show  whether  or  not  nitrates  are  present. 
If  they  are  not  present,  the  difference  between  the  total  N  and  theN 
present  as  NHs,  will  give  the  N  present  as  protein,  and  this  figure 
multiplied  by  6.25  will  give  the  amount  of  protein.     (See  note.) 

If  nitrates  are  present  it  is  generally  sufficient  to  report  the 
difference  between  the  total  nitrogen  and  the  ammoniacal  nitrogen 
as  "  protein  and  nitrate  nitrogen."  The  microscopical  examina- 
tion and  the  odor  on  burning  will  generally  give  indications 
as  to  whether  protein  is  present  or  not. 


486  TECHNICAL  METHODS  OF  ANALYSIS 

(d)  NITROGEN  AS  CYANIDE. — Cyanide  may  be  detected  quali- 
tatively by  acidifying  the  original  material  and  very  cautiously 
noting  the  odor.  If  cyanide  is  present,  digest  10  grams  of  the 
original  material  with  warm  water  and  wash  by  decantation  once 
or  twice,  pouring  the  liquid  through  a  filter.  Finally  transfer  the 
material  to  a  filter  and  wash  thoroughly  with  warm  water.  Cool 
to  room  temperature  and  determine  cyanogen  by  titrating  with 
0.1  N  AgNOs  as  described  on  page  31. 

NOTE. — If  cyanide  is  present,  the  total  N  as  previously  determined  will 
include  the  N  of  the  cyanide. 

Carbide. — The  presence  of  calcium  carbide  may  be  quali- 
tatively detected  by  the  odor  of  acetylene  when  the  material 
comes  in  contact  with  water.  An  approximately  quantitative 
estimation  may  be  obtained  by  collecting  the  acetylene  from  a 
weighed  amount  of  the  sample  under  water  in  a  nitrometer  tube. 
1  cc.  of  C2H2  at  0°  C.  and  760  mm.  pressure  is  equivalent  to 
0.002866  gram  of  CaC2. 

Sulfide  (Qualitative). — This  may  be  detected  by  the  odor  of 
H2S  when  the  material  is  acidified  with  HC1,  or  in  small  amounts 
by  the  blackening  of  filter  paper  moistened  with  lead  acetate 
solution. 

The  previous  examination  of  the  sample  will  generally  give 
indications  as  to  the  nature  of  the  sulfide.  The  amount  of  sulfur 
present  as  sulfide  may  be  determined  by  treating  2  grams  of  the 
material  with  dil.  HC1  and  bromine  water,  filtering,  and  deter- 
mining the  total  sulfate  in  the  filtrate  by  means  of  BaCb.  On  a 
separate  portion  determine  the  sulfur  present  as  sulfate.  The 
difference  between  these  two  determinations  shows  the  amount 
of  sulfur  present  as  sulfide. 

CUTTING  COMPOUNDS 

General. — These  materials  usually  consist  of  a  mixture  of  some 
fatty  oil  with  a  mineral  oil,  emulsified  by  means  of  soap  and,  as  a 
rule,  contain  40-60%  of  water.  The  soap  is  often,  though  not 
always,  a  potash  soap.  Whale  oil  and  lard  oil  are  the  fatty  oils 
generally  used. 

Moisture. — Dry  approximately  5  grams  in  a  flat  platinum  dish 
at  105°  C.  to  constant  weight.  The  loss  represents  moisture  and 
volatile  matter. 


MISCELLANEOUS  ANALYSES  487 

The  moisture  may  also  be  determined  by  the  Xylol  Method. 
(See  page  271.) 

Ash. — Ignite  the  residue  from  the  moisture  determination 
until  the  ash  is  white  or  light  gray  in  color.  Cool  in  a  desiccator 
and  weigh. 

Soap. — Titrate  the  ash  with  0.1NHC1  and  methyl  orange. 
Test  the  HC1  solution  with  a  platinum  wire  in  a  flame  to  see 
whether  the  base  is  Na  or  K.  Calculate  the  titration  to  the 
proper  soap. 

CALCULATION.— 1  cc.  0.1  N  HC1  =  0.0304  gram  Na  soap. 
1  cc.  0.1  N  HC1  =  0.0321  gram  K  soap. 

NOTE. — As  a  check  the  titration  should  also  be  calculated  to  sodium  or 
potassium  carbonate  and  the  weight  thus  calculated  should  agree  approx- 
imately with  the  weight  of  the  ash. 

CALCULATION.— 1  cc.  0.1  N  HC1=  0.00530  gram  Na2CO3. 

=  0.00691  gram  K2CO3. 

Total  Oily  Matter. — Weigh  out  about- 10  grams  into  a  200  cc. 
beaker,  add  100  cc.  of  water,  warm  on  the  steam  bath  and  add  an 
excess  of  dil.  H2S04.  Cool  the  mixture  and  transfer  to  a  separatory 
funnel.  Wash  the  beaker  finally  with  CHCls  and  add  the  wash- 
ings to  the  separatory  funnel.  Shake  out  3  times  with  portions 
of  about  30  cc.  of  CHCl^.  After  each  treatment  allow  the  two 
liquids  to  separate  completely  and  clearly  and  then  draw  off  the 
CHCla  extract  into  a  weighed  Soxhlet  flask.  Evaporate  the 
chloroform  from  the  combined  extracts  in  the  Soxhlet  flask,  dry 
to  constant  weight  at  105°  C.  and  weigh  the  total  oily  matter. 

Unsaponifiable  Oil. — Weigh  approximately  10  grams  into  a 
300  cc.  Erlenmeyer  flask,  add  50  cc.  of  0.5  N  alcoholic  KOH. 
Saponify  for  two  hours,  or  longer,  over  a  low  flame,  using  a  reflux 
condenser.  Add  a  few  drops  of  phenolphthalein  solution.  If  the 
mixture  in  the  flask  is  not  still  alkaline,  add  25  cc.  more  of  alcoholic 
KOH  and  saponify  for  another  two  hours.  The  mixture  should 
be  alkaline  after  the  saponification  is  complete.  Add  about  an 
equal  volume  of  water,  connect  the  flask  with  an  ordinary  Liebig 
condenser  and  distill  off  at  least  half  of  the  liquid.  Cool  the  residue 
and  transfer  to  a  large  separatory  funnel  and  dilute  with  several 
times  its  volume  of  cold  water.  Extract  the  solution  4  times  with 
portions  of  about  50  cc.  of  ether.  If  the  mixture  is  violently 
shaken  it  is  likely  to  form  an  emulsion  which  can  be  broken  up 


488  TECHNICAL  METHODS  OF  ANALYSIS 

only  with  difficulty.  Therefore  mix  the  two  by  giving  a  rotating 
motion  to  the  funnel  or  by  laying  it  on  its  side  and  rolling  it. 
Draw  off  the  ether  each  time  and  wash  once  with  water.  Pour 
the  combined  extracts  into  a  weighed  Soxhlet  flask,  evaporate  off 
the  ether  and  weigh. 

NOTE. — Instead  of  ether,  86°  Baume  naphtha  may  be  used.  This  is  less 
likely  to  form  emulsions,  but  care  should  be  taken  to  use  naphtha  which 
leaves  no  residue  on  evaporation  at  100°  C. 

Uncombined  Fatty  Oil. — This  is  obtained  by  calculation. 
Calculate  the  amount  of  fat  in  the  soap  present  by  using  the  fol- 
lowing factors: 

Combined  Fat  =  Na  Soap  X  0.93. 
=  K  Soap  X  0.88. 

Add  together  the  unsaponifiable  oil  and  the  fatty  oil  combined 
as  soap  and  subtract  the  sum  from  the  total  oily  matter.  The 
difference  represents  the  uncombined  fatty  oil. 

Free  Fatty  Acid. — Weigh  20  grams  into  a  300  cc.  Erlenmeyer 
flask,  add  100  cc.  of  alcohol  which  has  previously  been  warmed 
and  made  neutral  to  phenolphthalein  with  0.1  N  NaOH.  Warm 
the  mixture  on  the  steam  bath  for  about  one-half  hour,  titrate 
with  0.1  N  KOH  and  phenolphthalein  and  calculate  the  titration 
to  oleic  acid. 

CALCULATION.— 1  cc.  0.1  N  KOH  =  0.0282  gram  oleic  acid. 

METAL  POLISHES 

General. — Liquid  metal  polishes  may  be  divided  into  2  general 
classes : 

(1)  Naphtha  Polishes;  (2)  Fireproof  Polishes. 

The  former  consist  essentially  of  naphtha  containing  an  abrasive 
powder  held  in  suspension  by  means  of  soap  and  the  odor  of  the 
naphtha  covered  up  to  some  extent  by  an  essential  oil  such  as 
citronella  or  nitrobenzol.  The  second  class  is  for  the  most  part 
water  emulsions  of  various  solvents  holding  an  abrasive  powder  in 
suspension.  Carbon  tetrachloride  has  been  used  to  some  extent 
either  alone  or  in  combination  with  naphtha.  An  examination  of  a 
metal  polish  should  in  general  include  a  determination  of  the 
amount  and  character  of  the  solvents,  the  soap  and  the  abrasive. 

Solvents. — Weigh  out  100  grams  of  polish  into  a  250  cc.  dis- 
tilling flask  provided  with  a  thermometer  and  connected  with  a 


MISCELLANEOUS  ANALYSES 


489 


long  condenser.  Start  the  distillation  in  a  water  bath,  taking 
care  that  the  flame  is  amply  protected  from  any  uncondensed  vapors 
which  may  issue  from  the  end  of  the  condenser,  and  collect  the  dis- 
tillate in  a  25  cc.  tared  cylinder.  When  active  distillation  ceases, 
or  if  none  takes  place,  substitute  an  oil  bath  for  the  water  bath  and 
continue  the  distillation  up  to  250°  C.,  collecting  the  distillate 
in  tared  cylinders,  as  before.  The  following  fractions  should  be 
taken:  (1)  below  100°  C.;  (2)  100°-150°  C.;  (3)  150°-200°  C.; 
(4)  200°-250°  C. 

The  boiling  points,  odors,  refractive  indices  and  specific  grav- 
ities of  the  various  fractions  will  give  indications  of  the  character  of 
the  solvents.  Those  which  are  likely  to  be  present  are:  turpentine, 
pine  oil,  rosin  spirit,  rosin  oil,  naphtha,  kerosene,  carbon  tetra- 
chloride,  alcohol  and  water.  The  approximate  constants  of  these 
solvents  are  given  below : 


'. 
Specific 
Gravity 
at  15.5°  C. 

Distilling 
Temperature 
°C. 

Refractive  Index 

American  turpentine. 
Wood  turpentine  .... 
Pine  oil  
Rosin  spirit  

Rosin  oil  

0.860-0.870 
0.855-0.910 
0.935-0.947 
0.856-0.880 

0.96  -1.10 

155-170 
159-165 
190-220 
Gradual  rise 
(about  50% 
below  120°) 
300-360 

1.468-1.473  @20°C. 
1.468-1.475  @20°C. 
1.484-1.  486  @15.5°C. 

Naphtha  . 

0  700-0.750 

50-150 

Kerosene  
CC14  

0.775-0.800 
1.60 

150-300 

77 

Alcohol,  wood  
Alcohol,  denatured..  . 

About  0.800 
About  0.816 

About  65 
About  78 

NOTES. — (1)  Water  will  separate  from  all  other  constituents  except  alcohol. 
If  both  water  and  alcohol  are  present  the  amounts  can  be  roughly  approxi- 
mated by  taking  the  volume  and  sp.  gr.  of  the  aqueous  distillate  and  cal- 
culating from  the  sp.  gr.  tables  for  alcohol. 

(2)  If  water  is  present,  the  distilling  temperatures  will  be  no  indication 
of  the  boiling  points  of  the  other  substances  present. 

Soap. — Dry  15  grams  of  the  polish  on  a  Hofmeister  Schalchen, 
crush  and  extract  the  residue  with  ether  in  a  Soxhlet  extractor. 


490  TECHNICAL  METHODS  OF  ANALYSIS 

After  the  ether-soluble  materials  are  removed,  extract  the  soap 
with  alcohol  (95%).  Evaporate  off  the  alcohol,  dry  at  105°  C., 
and  weigh.  Examine  the  soap  to  determine  whether  it  is  a  sodium, 
potassium  or  ammonium  soap. 

In  case  no  alcohol-soluble  soap  is  obtained,  it  is  probable  that  a 
lime  soap  is  present,  in  which  case  the  contents  of  the  capsule 
should  be  acidified  with  1  cc.  of  cone.  HC1  and  extracted  with  ether. 
Evaporate  off  the  ether,  weigh  the  liberated  fatty  acids  and  cal- 
culate them  as  calcium  oleate. 

CALCULATION. — Fatty  acids XI. 07  =  calcium  oleate. 

Boil  the  acidified  contents  of  the  capsule  with  hot  water,  filter, 
and  make  a  qualitative  test  for  calcium. 

Free  Ammonia. — If  an  ammonium  soap  is  present  or  the  polish 
smells  of  NHa,  weigh  out  2-5  grams  of  the  original  polish  into  a 
flask,  add  200  cc.  of  water  and  distill  into  0.1  N  acid.  A  spray 
trap  should  be  used  and  a  few  drops  of  methyl  red  added  to  the 
acid.  Titrate  the  excess  acid  with  0.1  N  NaOH. 

CALCULATION — 1  cc.  0.1  N  acid  =  0.0017  gram  NH3. 

Combined  Ammonia. — Dilute  the  solution  remaining  in  the 
flask  with  200  cc.  of  water,  add  10  cc.  of  cone.  NaOH,  and  distill 
as  before.  Calculate  to  NB^  soap. 

CALCULATION. — 1  cc.  0.1  N  acid  =  0.03  gram  NH4  soap. 

Abrasive. — Weigh  out  10  grams  of  the  metal  polish,  evaporate 
to  dryness,  taking  proper  precautions  if  the  solvent  is  an  inflam- 
mable one,  ignite  at  a  low  red  heat  to  burn  off  any  organic  matter, 
and  weigh.  Correct  the  ash  thus  formed  for  the  ash  of  the  soap, 
unless  an  ammonia  soap  is  present.  Examine  the  ash  microscop- 
ically to  ascertain  if  it  consists  of  tripoli  or  ground  rock.  If  the 
latter,  a  qualitative  analysis  may  be  made;  although  the  physical 
condition  of  the  abrasive  is  of  more  importance  than  its  chemical 
composition. 

NOTE. — It  should  be  remembered  that  all  of  the  determinations  are  more 
or  less  approximate,  due  to  various  causes,  and  consequently  calculations 
should  be  made  to  the  nearest  even  percentage. 

SOLDERING  PASTE 

General. — Soldering  pastes  generally  consist  of  a  mixture  of 
and  NH4C1  with  petrolatum.     While  they  vary  somewhat 


MISCELLANEOUS  ANALYSES  491 

in  composition  their  proportions  are  generally  within  the  following 

limits : 

ZnCl2 15-20% 

NH4C1 1-  5% 

Water Less  than  5% 

Since  the  salts  are  likely  to  settle  out  on  standing,  especially 
if  the  paste  has  been  in  a  warm  place,  it  is  necessary  before  start- 
ing the  analysis  to  make  sure  that  the  material  is  very  thoroughly 
and  completely  mixed. 

Water. — Determine  the  water  by  the  Xylol  Method  as  in  the 
analysis  of  Greases  (page  271). 

Total  Ammonia. — Weigh  out  30-40  grams  of  the  paste  in  a 
beaker  and  transfer  to  a  separatory  funnel  by  means  of  a  hot  5% 
solution  of  HNOs.  About  200  cc.  of  the  acid  should  be  employed. 
Shake  out  the  paste  thoroughly  with  the  acid  and  let  the  layers 
separate.  Draw  off  the  solution  into  a  liter  graduated  flask. 
Repeat  the  shaking  out  of  the  melted  paste  in  the  funnel  3  times 
with  fresh  portions  of  about  200  cc.  of  the  hot  acid.  Cool  the 
solution  in  the  flask  to  room  temperature  and  dilute  with  distilled 
water  to  the  mark.  Use  aliquots  of  this  solution  for  the  deter- 
mination of  total  NHs,  total  Cl  and  Zn. 

For  the  NHs  determination,  pipette  200  cc.  into  a  Kjeldahl  dis- 
tilling -flask,  add  a  few  drops  of  methyl  orange  and  make  distinctly 
alkaline  with  NaOH,  adding  at  the  same  time  a  few  grains  of 
metallic  zinc  to  prevent  bumping.  Distill  in  the  usual  manner, 
collecting  the  distillate  in  50  cc.  of  0.1  N  acid.  Titrate  back  the 
excess  of  acid  with  0.1  N  alkali  and  calculate  the  acid  neutralized 
during  the  distillation  to  NHs  and  also  to  NHiCl.  Divide  the 
weights  thus  obtained  by  0.2  of  the  weight  of  the  original  sample 
and  multiply  by  100  to  obtain  the  percentages. 

CALCULATION.— 1  cc.  of  0.1  N  acid  =  0.001703  gram  NH3. 

=  0.005350  gram  NH4C1. 

Zinc  Chloride. — Pipette  100  cc.  of  the  acid  solution  into  a  350 
cc.  beaker.  Add  a  slight  excess  of  NEUOH  and  heat  to  boiling. 
Filter  if  there  is  a  precipitate  of  iron  and  aluminum  hydroxides. 
Make  the  filtrate  faintly  acid  with  acetic  acid;  then  add  a  large 
excess  of  ammonium  phosphate  and  boil  the  solution  until  the 
precipitate  of  ZnNHiPC^  is  crystalline.  Let  settle  until  clear. 


492  TECHNICAL  METHODS  OF  ANALYSIS 

Filter  on  a  Gooch  crucible;  wash  with  hot  water  and  dry  in  the 
oven.  Finally  ignite  strongly  to  constant  weight  and  weigh  as 
Zn2P207.  Calculate  to  ZnCb;  divide  by  0.1  of  the  weight  of  the 
original  sample  taken  and  multiply  by  100  to  obtain  the  per- 
centage of  ZnCb. 

CALCULATION.— Zn2P2O7  X  0.8943  =  ZnCl2. 

Total  Chlorine. — It  is  not  generally  necessary  to  determine  the 
total  chlorine  unless  it  is  desired  to  check  up  the  previous  deter- 
minations or  unless  NaCl  is  suspected  to  be  present.  For  the 
determination,  pipette  50  cc.  of  the  HNOs  solution  into  a  clean  por- 
celain dish  or  casserole.  Add  sufficient  pure  CaCOs  to  neutralize 
all  the  acid  present  and  still  have  an  excess  of  the  CaCOs  undis- 
solved.  Then  add  about  5  cc.  of  K2CrC>4  indicator  solution  and 
titrate  the  Cl  with  0.1  N  AgNOs  until  a  permanent  reddish  color 
appears  in  the  solution.  The  end  point  can  best  be  determined 
in  the  presence  of  artificial  light.  Calculate  the  amount  of  chlorine 
to  which  the  titration  corresponds.  Divide  this  weight  by  0.05 
of  the  weight  of  the  original  sample  and  multiply  by  100  to  obtain 
the  percentage  of  Cl. 
CALCULATION.— 1  cc.  0.1  N  AgNO3  =  0.003546  gram  Cl. 

NOTE. — The  total  Cl  of  course  should  check  closely  the  amount  of  Cl 
equivalent  to  the  ZnCl2  and  NH4C1  determined.  If  it  is  in  excess,  the  mate- 
rial should  be  tested  for  Na,  and,  if  present,  the  excess  Cl  calculated  to  NaCl. 

CALCULATIONS--NH4C1 X  0.6628  =  Cl. 
ZnCl2X0.5.204  =C1. 
ClX  1.6486  =NaCl. 


SANITARY  ANALYSIS  OF  WATER  AND  SEWAGE 

General. — Before  making  a  sanitary  analysis  of  a  sample  of 
water,  the  general  characteristics  of  the  water  should  be  noted. 
All  substances  which  are  likely  to  undergo  change  should  be 
determined  as  quickly  as  possible.  This  includes  free  and  albu- 
minoid ammonia,  nitrites,  nitrates  and  oxygen  consumed  (also 
free  C02  and  alkalinity  or  acidity  when  desired) . 

The  determinations  included  in  the  usual  sanitary  water 
analysis  are  given  below  and  the  form  of  reporting  and  the  num- 
ber of  significant  figures  to  be  reported  are  also  indicated : 


MISCELLANEOUS  ANALYSES  493 

Sediment X.X 

Turbidity X.X 

Odor '... "  ....  .- 

Color XX 

Parts  per  100,000 

Residue  on  Evaporation X.XX 

Nitrogen  as  Free  Ammonia X.XXXX 

Albuminoid  Ammonia X.XXXX 

Nitrites X.XXXX 

Nitrates ' X.XXXX 

Oxygen  Consumed X.XX 

Chlorine X.XX 

Hardness X.X 

Iron X.XXXX 

Odor. — The  observation  of  the  odor  of  cold  and  hot  samples  of 
surface  waters  is  very  important,  as  the  odors  are  usually  connected 
with  some  organic  growths  or  with  sewage  contamination,  or 
both.  The  odor  of  ground  waters  is  often  caused  by  the  earthy 
constituents  of  the  water-bearing  strata.  The  odor  of  a  con- 
taminated well  water  is  often  a  contributary  evidence  of  its  pol' 
lution. 

COLD.  ODOR. — Shake  the  sample  violently  in  one  of  the  gallon 
collecting  bottles,  about  half  or  two-thirds  full  of  the  water  at 
room  temperature  (about  20°  C.).  Remove  the  stopper  and 
smell  the  odor  at  the  mouth  of  the  bottle. 

HOT  ODOR. — Into  a  tall  400  cc.  beaker  without  lip,  pour  about 
150  cc.  of  the  sample.  Cover  the  beaker  with  a  well-fitting 
watch  glass,  place  on  a  hot  plate  and  bring  the  water  to  just  below 
boiling.  Remove  the  beaker  from  the  plate  and  let  it  cool  for  not 
more  than  five  minutes.  Then  shake  with  a  rotary  movement, 
slip  the  watch  glass  to  one  side  and  note  the  odor. 

EXPRESSION  OF  RESULTS. — Express  the  quality  of  the  odor  by 
some  such  descriptive  term  as  the  following;  vegetable,  aromatic, 
grassy,  fishy,  earthy,  moldy,  musty,  disagreeable,  peaty,  sweetish, 
sulfide,  etc. 

Sediment  and  Suspended  Matter. — Ordinarily  the  sediment 
may  be  expressed  qualitatively  as  slight,  flocculent,  considerable, 
or  heavy.  If  quantitative  results  are  desired,  filter  a  measured 


494  TECHNICAL    METHODS  OF  ANALYSIS 

quantity  of  the  water  after  shaking  (500  cc.  are  suitable)  through  a 
filter  paper  which  has  previously  been  dried  in  a  weighing  bottle 
in  the  oven  to  constant  weight.  Then  dry  the  filter  containing  the 
sediment  to  constant  weight,  at  the  same  temperature.  This 
gives  the  total  suspended  matter.  If  the  mineral  suspended  matter 
is  desired,  ignite  in  a  platinum  crucible  and  weigh. 

Turbidity. — The  turbidity  is  due  to  suspended  matter  such  as 
clay,  silt,  finely  divided  matter,  microscopic  organisms,  etc.  The 
standard  of  turbidity  adopted  by  the  U.  S.  Geological  Survey  is 
a  water  which  contains  100  parts  of  silica  per  million  in  such 
a  state  of  fineness  that  a  bright  platinum  wire,  1  mm.  in  diameter, 
can  just  be  seen  when  the  center  of  the  wire  is  100  mm.  below  the 
surface  of  the  water  and  the  eye  of  the  observer  is  1.2  meters  (about 
4  feet)  above  the  wire;  the  observation  being  made  in  the  middle 
of  the  day,  in  the  open  air  but  not  in  sunlight,  and  in  a  vessel  so 
large  that  the  sides  do  not  shut  out  the  light.  The  turbidity  of 
such  a  water  is  arbitrarily  fixed  at  100. 

The  number  obtained  by  dividing  the  weight  of  suspended 
matter  in  the  sample,  in  parts  per  million,  by  the  turbidity,  is 
called  the  Coefficient  of  Fineness.  If  greater  than  1,  it  indicates 
that  the  matter  in  suspension  is  coarser  than  the  standard;  if 
less  than  1,  that  it  is  finer. 

SILICA  STANDARDS. — To  prepare  the  standard,  use  precipitated 
fuller's  earth,  dry  and  sift  through  a  200-mesh  sieve.  One  gram 
of  this  preparation  in  1  liter  of  distilled  water  makes  a  stock  sus- 
pension containing  1000  parts  of  silica  per  million,  which  should 
have  turbidity  of  1000.  Test  this  suspension,  after  diluting 
a  portion  of  it  with  9  times  its  volume  of  distilled  water,  with  a 
platinum  wire  as  described  below  to  ascertain  if  the  silica  has 
the  necessary  degree  of  fineness  and  if  the  suspension  has  the 
necessary  degree  of  turbidity.  If  not,  correct  by  adding  more 
silica  or  more  water  as  required. 

Prepare  standards  for  comparison  from  the  stock  suspension 
by  diluting  with  distilled  water.  For  turbidity  readings  below  20, 
keep  standards  of  0,  5,  10,  15,  and  20  in  the  same  size  bottles  as 
are  used  in  collecting  the  samples.  For  readings  above  20, 
keep  standards  of  20,  30,  40,  50,  60,  70,  80,  90,  and  100  in  100  cc. 
Nessler  tubes  approximately  20  mm.  in  diameter.  In  comparing 
the  water  under  examination  with  the  standards,  take  an  amount 


MISCELLANEOUS  ANALYSES  495 

equivalent  to  the  standard,  view  the  liquids  sidewise  towards  the 
light,  looking  at  some  object,  and  note  the  distinctness  with  which 
the  margins  of  the  object  may  be  seen.  Keep  the  standard  stop- 
pered and  shake  both  sample  and  standard  thoroughly  before 
making  the  comparison. 

NOTE. — In  order  to  prevent  growth  of  bacteria  or  algae  in  the  standards, 
a  small  amount  of  mercuric  chloride  may  be  added  to  them. 

PLATINUM  WIRE  METHOD. — The  platinum  wire  method  of 
determining  turbidity  may  be  used  directly  on  the  sample  instead 
of  preparing  standards  as  above.  It  is  the  method  to  be  used  in 
ascertaining  the  correctness  of  the  stock  suspension  above  de- 
scribed. 

This  method  requires  a  rod  with  a  platinum  wire  of  1  mm.  diam- 
eter (0.04  inch,  No.  18  B.  &  S.  gauge)  inserted  in  it  about  1  inch 
above  the  end  of  the  rod  and  projecting  from  it  at  least  25  mm.  at  a 
right  angle.  Near  the  end  of  the  rod,  at  a  distance  of  1.2  meters 
(about  4  feet)  from  the  platinum  wire,  place  a  wire  ring  directly 
above  the  wire.  When  making  the  examination  look  through  this 
ring  with  the  eye  directly  above  it.  Graduate  the  ring  as  follows : 
At  a  distance  of  100  mm.  from  the  center  of  the  wire,  mark  100. 
If  desired,  other  graduations  may  be  made  according  to  the  table 
below  or  the  distance  may  be  measured  in  mm.  and  the  turbidity 
calculated. 

Procedure. — Lower  the  rod  vertically  into  the  water  as  far 
as  the  wire  may  be  seen,  and  then  read  the  level  of  the  surface  of 
the  water  on  the  graduated  scale  (or  mark  the  point  and  measure 
the  distance).  The  following  precautions  must  be  taken  to  insure 
correct  results: 

Observations  must  be  made  in  the  open  air,  preferably  in  the 
middle  of  the  day  and  not  in  direct  sunlight.  The  wire  must  be 
kept  bright  and  clean.  If  for  any  reason  observations  cannot  be 
made  under  natural  conditions  directly,  a  pail  or  tank  may  be 
filled  with  water  and  the  observation  taken  in  that,  but  in  this 
case  care  must  be  taken  that  the  water  is  thoroughly  stirred 
before  the  observation  is  made,  and  no  vessel  is  to  be  used  for  this 
purpose  unless  its  diameter  is  at  least  twice  as  great  as  the  depth 
to  which  the  wire  is  immersed.  Waters  which  have  a  turbidity 
above  500  must  be  diluted  with  clear  water  before  the  observations 


496 


TECHNICAL  METHODS  OF  ANALYSIS 


are  made;    but  in  case  this  is  done,  the  degree  of  dilution  used 
should  be  stated  and  form  a  part  of  the  report. 


Turbidity,  Parts  per 
Million 

Vanishing  Depth 
of  Wire,  mm. 

Turbidity,  Parts 
per  Million 

Vanishing  Depth 
of  Wire,  mm. 

7 

1095 

70 

138 

8 

971 

75 

130 

9 

983 

80 

122 

10 

794 

85 

116 

11 

729 

90 

110 

12 

674 

95 

105 

13 

627 

100 

100 

14 

587 

110 

93 

15 

551 

120 

86 

16 

520 

130 

81 

17 

493 

140 

76 

18 

468 

150 

72 

19 

446 

160 

68.7 

20 

426 

180 

62.4 

22 

391 

200 

57.4 

24 

361 

250 

49.1 

26 

336 

300 

43.2 

28 

314 

350 

38.8 

30 

296 

400 

35.4 

35 

257 

500 

30.9 

40 

228 

600 

27.7 

45 

205 

800 

23.4 

50 

187 

1000 

20.9 

55 

171 

1500 

17.1 

60 

158 

2000 

14.8 

65 

147 

3000 

12.1 

The  wire  method  is  to  be  used  for  testing  the  degree  of  fineness 
of  the  standard  silica,  and  this  should  be  such  that  when  added 
to  distilled  water  in  an  amount  equal  to  100  parts  per  million,  the 
wire  observed  under  standard  conditions  can  be  just  seen  at  a 
depth  of  100  mm.  below  the  surface  of  the  water. 


MISCELLANEOUS  ANALYSES  497 

Color. — The  "  true  color  "  of  water  is  considered  that  part  of 
the  apparent  color  which  is  due  only  to  substances  in  solution,  i.e., 
it  is  the  color  of  water  after  filtration.  The  "  apparent  color  " 
is  the  color  as  viewed  by.  inspection  of  the  original  sample.  In 
stating  the  results,  the  word  "  color  "  means  the  color  of  the  fil- 
tered sample,  unless  otherwise  expressed. 

PLATINUM-COBALT  STANDARD. — The  platinum-cobalt  method  of 
measuring  color  is  the  standard  and  the  unit  of  color  is  that  pro- 
duced by  one  part  of  platinum  per  million. 

Prepare  the  standard  solution  (which  has  a  color  of  500) 
as  follows:  Dissolve  in  water  1.246  grams  of  K^PtCle  (containing 
0.5  gram  of  Pt),  1  gram  of  crystallized  CoCb-GH^O  (containing 
0.25  gram  of  Co)  and  100  cc.  of  cone.  HC1,  and  dilute  with  dis- 
tilled water  to  1  liter.  Place  varying  aliquots  of  this  solution  in 
Nessler  tubes  and  dilute  with  distilled  water  to  the  100  cc.  mark. 
These  diluted  solutions  should  have  colors  of  0,  5,  10,  15,  20,  25, 
30,  35,  40,  50,  60,  and  70,  respectively.  The  tubes  must  be  of  such 
size  that  the  100  cc.  mark  is  between  20  and  25  cm.  above  the  bot- 
tom and  is  uniform  for  all  tubes.  Protect  these  standard  tubes 
from  dust  when  not  in  use. 

Procedure. — Fill  a  clean  Nessler  tube  with  the  sample  to  the 
height  equal  to  that  in  the  standard  tubes,  and  compare  the  color 
with  the  standards.  The  observation  must  be  made  by  looking 
vertically  downward  through  the  tubes  upon  a  white  surface 
placed  at  such  an  angle  that  light  is  reflected  upward  through 
the  column  of  liquid.  Estimate  the  color  of  the  water  from  the 
standards  which  most  nearly  match  it. 

NOTES. — (1)  Waters  that  have  a  color  darker  than  70  must  be  diluted 
before  making  the  comparison. 

(2)  Water  containing  suspended  matter  must  be  filtered  until  no  visible 
turbidity  remains  before  the  observation  is  made.  If  the  suspended  matter 
is  coarse,  use  filter  paper;  if  fine,  a  Berkefeld  filter  is  recommended.  The 
Pasteur  filter  must  not  be  used,  as  it  has  a  decolorizing  effect. 

Chemical  Analysis. — Express  results  of  chemical  analysis  in 
parts  per  100,000. 

RESIDUE  ON  EVAPORATION  (TOTAL  SOLIDS). — Evaporate  100  cc. 

of  the  sample  in  a  weighed  platinum  dish  on  the  water  bath.     If 

the  water  has  a  high  Mg  content,  add  25  cc.  of  0.02  N  Na2COs 

solution,*  correcting  for  this  in  the  final  calculation.     Dry  the 

*  This  prevents  the  hydrolysis  of  MgClz  and  loss  of  HQ. 


498  TECHNICAL  METHODS  OF  ANALYSIS 

residue  for  one-half  hour  at  a  temperature  of  about  103°  C. 
Cool  in  a  desiccator  over  cone.  H2SO4  and  weigh. 

Loss  ON  IGNITION. — Heat  the  platinum  dish  with  the  residue  in 
a  "  radiator/'  which  consists  of  another  platinum  dish  large  enough 
to  allow  an  air  space  of  about  0.5  inch  between  the  inner  and  outer 
dishes,  the  inner  dish  being  supported  by  a  triangle  of  platinum 
wire  laid  on  the  bottom  of  the  outer  dish.  Suspend  over  the  inner 
dish  a  disk  of  platinum  foil  large  enough  to  cover  the  outer.  Heat 
the  large  dish  to  bright  redness  until  the  residue  is  white  or  nearly 
so.  Let  cool,  moisten  the  residue  with  a  few  drops  of  distilled 
water,  dry  in  the  oven  for  one-half  hour,  cool  and  weigh.  The 
difference  between  this  and  the  total  solids  is  the  "  loss  on  igni- 
tion." 

NOTES. — (1)  An  electric  muffle  furnace  may  be  used  in  place  of  the 
radiator. 

(2)  It  is  not  customary  to  report  the  loss  on  ignition  but  it  is  of  value  in 
interpreting  the  analysis.  The  manner  in  which  the  residue  behaves  as  to 
odor  and  color  upon  ignition  should  be  noted,  as  it  often  gives  a  helpful  clue 
to  the  character  of  the  organic  matter. 

NITROGEN  AS  FREE  AMMONIA 

General. — There  are  two  methods  for  estimating  nitrogen  as 
free  ammonia:  (A)  by  distillation,  and  (B)  by  direct  nessleriza- 
tion.  The  former  is  recommended  for  most  waters,  while  the 
latter  is  preferable  for  sewages,  sewage  effluents,  and  highly  pol- 
luted surface  waters. 

I.  Free  Ammonia  by  Distillation. — Connect  a  liter  round- 
bottom  flask  to  a  block  tin  or  aluminum  condenser  in  such  a 
way  that  the  distillate  may  be  conveniently  delivered  into 
Nessler  tubes.  Free  the  apparatus  from  NHs  by  boiling  distilled 
water  in  it  until  the  distillate  shows  no  further  traces  of  free  NHs. 
Then  empty  the  distilling  flask  and  measure  into  it  500  cc.  of  the 
sample,  or  a  smaller  portion  diluted  to  500  cc.  Apply  the  heat  so 
that  the  distillation  will  be  at  the  rate  of  6-10  cc.  per  minute. 
Collect  three  *  Nessler  tubes  of  the  distillate,  50  cc.  to  each  portion. 
These  contain  the  free  NHs,  to  be  measured  as  described  below. 

*  If  the  free  NH3  is  unusually  high,  it  may  be  necessary  to  collect  more 
than  3  tubes  of  distillate.  The  last  tube  should  be  free  or  practically  free 
from  NH3. 


MISCELLANEOUS  ANALYSES  499 

NOTE. — If  the  sample  is  acid  or  if  the  presence  of  urea  is  suspected,  add  about 
0.5  gram  of  Na2COs  previous  to  distillation.  Omit  this  when  possible  as  it 
tends  to  increase  bumping.  Use  only  Nessler  tubes  which  do  not  show  a 
variation  of  more  than  6  mm.  (0.25  inch)  in  the  distance  which  the  50  cc. 
graduation  mark  is  above  the  bottom.  The  tubes  must  be  of  clear  white 
glass  with  polished  bottoms. 

The  comparison  of  the  distillates  may  be  made  either  (1) 
against  nesslerized  solutions  containing  known  quantities  of 
N  as  NHiCl  or  (2)  against  permanent  standard  solutions  in 
which  the  colors  of  nesslerized  standard  ammonia  colors  are 
duplicated  by  solutions  of  Pt  and  Co  chlorides.. 

(1)  Comparison  with  Ammonia  Standards. — (A)  REAGENTS. — 
For  comparison  with  ammonia  standards,  prepare  the  following 
reagents : 

(a)  Ammonia-free  water. 

(b)  Standard  NH4Cl  solution.— Dissolve  3.82  grams  of  NILiCl 
in  1  liter  of  distilled  water  and  dilute  10  cc.  of  this  to  1  liter  with 
ammonia-free  water.     1  cc.  of  the  final  solution  equals  0.00001 
gram  of  N. 

(c)  Nessler' s  reagent. — Dissolve  50  grams  of  KI  in  a  minimum 
quantity   of  cold   water.     Add   a  saturated   solution   of  HgCk 
until  a  slight  permanent  precipitate  forms.     Add  400  cc.  of  50% 
KOH  solution,  made  by  dissolving  the  KOH  and  allowing  it  to 
settle  clear  before  using.     Then  dilute  to  1  liter,  let  settle  and 
decant.     This   solution  should  give  the  required  color  with  ammo- 
nia within  five  minutes  after  addition  and  should  not  precipitate 
with  small  amounts  of  NHs  within  two  hours. 

(B)  PROCEDURE. — Prepare  a  series  of  16  Nessler  tubes  which 
contain  the  following  number  of  cc.  of  the  standard  NH4C1  solu- 
tion, diluted  to  50  cc.  with  ammonia-free  water,  namely,  0.0,  0.1, 
0.3,  0.5,  0.7,  1.0,  1.4,  1.7,  2.0,  2.5,  3.0,  3.5,  4.0,  4.5,  5.0  and  6.0. 
These  will  contain  0.00001  gram  of  N  for  each  cc.  of  the  standard 
solution  used. 

Nesslerize  the  standards  and  also  the  distillates  from  the 
sample  by  adding  approximately  2  cc.  of  Nessler's  reagent  to 
each  tube.  Do  not  stir  the  contents  of  the  tubes.  Have  the 
temperature  of  the  tubes  practically  the  same  as  that  of  the 
standard,  otherwise  the  colors  will  not  be  directly  comparable. 
Let  the  tubes  stand  for  at  least  ten  minutes  after  nesslerizing. 
Compare  the  color  produced  in  these  tubes  with  that  of  the  stand- 


500  TECHNICAL  METHODS  OF  ANALYSIS 

ards  by  looking  vertically  downward  through  them  at  a  white  sur- 
face placed  at  an  angle  in  front  of  the  window  so  as  to  reflect  the 
light  upwards. 

In  case  the  color  obtained  by  nesslerizing  the  distillates 
is  greater  than  that  of  the  darkest  standard,  mix  the  contents  of 
the  tube  thoroughly  and  pour  out  one-half.  Make  up  the  remain- 
der to  the  original  volume  with  ammonia-free  water.  Then  make 
the  color  comparison  and  multiply  the  result  by  2.  If  the 
color  is  still  too  dark,  repeat  the  process  of  division  until  a  read- 
ing can  be  made.  In  case  the  color  of  the  distillates  is  too 
high,  this  process  may  be  shortened  by  mixing  together  all  of  the 
distillates  in  one  sample  before  making  the  comparison,  then 
taking  an  aliquot  portion  for  comparing  with  the  standards. 

If  a  precipitate  is  formed,  dilute  the  reagent  before  adding  it  to 
the  tubes. 

After  the  readings  have  been  made  and  recorded,  add  together 
the  results  obtained  on  separate  tubes  of  the  sample  to  get  the 
total  number  of  cc.  of  standard  required.  If  500  cc.  of  the  sample 
were  distilled,  multiply  this  sum  by  0.002  to  get  the  parts  of 
N  as  free  NHa  per  100,000  parts  of  the  sample. 

(2)  Permanent  Standards. — Permanent  standards  for  com- 
parison may  be  prepared  as  below  and  the  colors  of  the  nesslerized 
distillates  compared  with  these  after  the  former  have  stood  about 
ten  minutes. 

(A)  REAGENTS. — (1)  Platinum  Solution. — Dissolve  2  grams  of 
K2PtCl6  in  a  small  amount  of  distilled  water.     Add  100  cc.  of 
cone.  HC1  and  dilute  to  1  liter.' 

(2)  Cobalt  Solution.— Dissolve  12  grams  of  CoCl2-6H2O  in 
distilled  water,  add  100  cc.  of  cone.  HC1  and  dilute  to  1  liter. 

(B)  PROCEDURE. — For  the  standards  place  varying  amounts  of 
these  two  solutions  in  Nessler  tubes  and  fill  up  to  the  50  cc.  mark 
with  distilled  water  as  shown  in  the  table  on  page  501. 

The  amounts  stated  here  are  approximate,  and  the  actual 
amount  necessary  will  vary  with  the  character  of  the  Nessler  solu- 
tion used,  with  the  color  sensitiveness  of  the  analyst's  eye,  and 
with  the  other  incidental  conditions.  The  final  test  of  the  stand- 
ard is  best  obtained  by  comparing  it  with  nesslerized  standards 
and  modifying  the  tint  accordingly.  Such  a  comparison  should 
be  made  for  each  new  batch  of  Nessler  solution  and  should  be 
checked  by  each  analyst. 


MISCELLANEOUS  ANALYSES 


501 


Equivalent  Volume  of 
Standard  NH4C1  Solution 
cc. 

Platinum  Solution 
cc. 

Cobalt  Solution 
cc. 

0.0 

1.2 

0.0 

0.1 

1.8 

0.0 

0.2 

2.8 

0.0 

0.4 

4.7 

0.1 

0.7 

5.9 

0.2 

1.0 

7.7 

0.5 

1.4 

9.9 

1.1 

1.7 

11.4 

1.7 

2.0 

12.7 

2.2 

2.5 

15.0 

3.3 

3.0 

17.3 

4.5 

3.5 

19.0 

5.7 

4.0 

19.7 

7.1 

4.5 

19.9 

8.7 

5.0 

20.0 

10.4 

6.0 

20.0 

15.0 

7.0 

20.0 

22.0 

It  is  necessary  to  use  tubes  which  have  the  50  cc.  mark  not 
less  than  20  nor  more  than  22  cm.  above  the  bottom.  These 
standards  may  be  kept  for  several  months  if  protected  from  dust. 
The  method  of  calculating  results  is  precisely  the  same  as  with 
the  ammonia  standards. 

II.  Free  Ammonia  by  Direct  Nesslerization. 

(1)  REAGENTS. 

(a)  CuS04  (10%  solution) 

(6)  Lead  acetate  (10%  solution) 

(c)  NaOH  or  KOH  (50%  solution) 

(d)  MgCl2  (10%  solution). 

(2)  PROCEDURE  (FOR  SEWAGE). — Mix  50  cc.  of  the  sample  with 
an  equal  volume  of  water,  place  in  a  short  Nessler  tube  and  add  a 
few  drops  of  CuSC^  solution.     After  thoroughly  mixing,  add  1  cc. 
of  the  caustic  solution  and  again  thoroughly  mix.     Let  stand  for 
a  few  moments.     A  heavy  precipitate  should  fall  to  the  bottom, 


502  TECHNICAL  METHODS  OF  ANALYSIS 

leaving  a  colorless  supernatant  liquid.  Nesslerize  an  aliquot  por- 
tion of  this  clear  liquid. 

Many  samples  containing  H^S  require  the  use  of  lead  acetate 
in  addition  and  others  require  a  few  trials  before  the  right  com- 
bination of  the  three  solutions  to  bring  about  the  best  results  can 
be  made.  In  place  of  adding  CuSO4  to  sewages  of  high  Mg  con- 
tent, satisfactory  clarification  may  often  be  obtained  by  mixing 
with  the  caustic  alone. 

The  amount  of  N  as  free  NHs  is  computed  after  comparison 
with  standards  in  the  same  manner  as  in  the  distillation  procedure. 

NITROGEN  AS  ALBUMINOID  AMMONIA 

General. — The  addition  of  an  alkaline  permanganate  solution 
to  liquids  containing  nitrogenous  organic  matter  causes  the  forma- 
tion of  NHs,  the  amount  of  which  can  be  measured  upon  distillation 
of  the  treated  sample  and  nesslerization  of  the  distillate.  In 
sewages  and  other  liquids  and  substances  containing  considerable 
nitrogenous  organic  matter,  the  percentage  of  nitrogenous  material 
which  is  ammonia-forming  is  decidedly  variable.  For  this  reason 
albuminoid  NHs  results  in  such  cases  are  less  valuable  than  the 
total  organic  N,  sometimes  called  the  Kjeldahl  nitrogen.  Hence, 
for  sewage  work,  including  the  analyses  of  both  the  influents  and 
the  effluents  of  purification  plants,  as  well  as  the  study  of  highly 
polluted  streams,  it  is  recommended  that  albuminoid  NHs  deter- 
minations be  omitted  and  in  their  place  the  total  organic  N  be 
determined. 

For  ground  waters  and  surface  waters  containing  but  little 
pollution,  the  N  as  albuminoid  NHs  quite  uniformly  approxi- 
mates about  one-half  of  the  total  organic  N.  Accordingly  the 
continuance  of  albuminoid  NHs  determinations  for  this  class  of 
work  is  approved.  Nevertheless  the  inferiority  of  such  results 
to  those  of  total  organic -N  is  recognized. 

Reagent. — Alkaline  KMnO±. — Pour  1200  cc.  of  distilled  water 
in  a  porcelain  dish  holding  2500  cc.,  boil  ten  minutes  and  turn  off 
the  gas.  Add  16  grams  of  c.  P.  KMnC>4  and  stir  until  dissolved. 
Then  add  800  cc.  of  a  50%  clarified  solution  of  NaOH  or  KOH 
and  enough  distilled  water  to  fill  the  dish.  Boil  down  to  2000  cc. 
Test  each  batch  of  this  solution  for  albuminoid  NHs  by  making 
a  blank  determination  and  correct  for  this  blank  in  the  analysis. 


MISCELLANEOUS  ANALYSES  503 

Procedure. — Interrupt  the  distillation  (made  as  already 
described)  after  the  collection  of  the  distillate  for  free  NHs,  add 
40  cc.  or  more  of  alkaline  KMnCU  and  continue  the  distillation 
until  at  least  4  portions  of  50  cc.  each,  and  preferably  5  portions, 
of  the  distillate  have  been  collected  in  separate  tubes.  Have 
enough  permanganate  solution  present  to  insure  the  maximum 
oxidation  of  the  organic  matter.  Determine  the  N  in  the  dis- 
tillates as  previously  described  and  express  the  results  as  in  the 
case  of  free  NHs. 

NOTES. — (1)  Dissolved  N  as  albuminoid  NH3  may  be  determined  from  a 
sample  from  which  suspended  matter  has  been  removed  by  filtration  either 
through  filter  paper,  or,  if  finely  divided  matter  is  present,  through  a  Berkefeld 
filter. 

(2)  Suspended  N  as  albuminoid  NHs  may  be  obtained  by  taking  the  dif- 
ference between  the  total  and  dissolved  N. 

TOTAL  ORGANIC  NITROGEN 

Procedure  for  Water. — Boil  500  cc.  of  the  sample  in  a  round- 
bottom  flask  until  free  from  NHs.  This  usually  requires  the  dis- 
tillation of  about  200  cc.  of  the  sample,  which  is  to  be  collected 
for  the  determination  of  free  NHs. 

Add  5  cc.  of  c.  P.  cone.  H2SO4,  free  from  N,  together  with  a 
small  piece  of  ignited  pumice.  Mix  by  shaking  and  place  over  a 
flame  under  a  hood.  Digest  until  copious  fumes  of  SOs  are  given 
off  and  until  the  liquid  chars  and  finally  becomes  colorless.  Remove 
from  the  flame  and  add  KMnO4  crystals  in  small  portions  until 
a  heavy  green  precipitate  persists  in  the  liquid.  Cool,  dilute 
with  about  100  cc.  of  ammonia-free  water  and  neutralize  with  10% 
ammonia-free  Na2COs  solution.  Distill  off  the  NHs,  collect  in 
Nessler  tubes,  nesslerize  and  compare  with  standards  as  already 
described. 

Procedures  for  Sewage. — METHOD  I.— Distill  the  free  NHs 
by  passing  live  steam  through  100  cc.  or  less  of  the  sample.  Collect 
the  distillate,  and  determine  the  free  NHs  in  it.  Add  5  cc.  of 
H2S04  and  1  cc.  of  10%  CuSCU  solution,  and  digest  for  one-half 
hour  after  the  whole  has  become  colorless.  Add  0.5  gram  of 
KMnO4  crystals  to  the  hot  acid  residue  in  the  flask  and  dilute 
to  500  cc.  in  a  volumetric  flask.  Place  10  cc.  or  more  of  this 
liquid  in  a  200  cc.  Kjeldahl  distilling  flask.  Dilute  with  100  cc. 


504  TECHNICAL  METHODS  OF  ANALYSIS 

of  water,  neutralize  with  10  cc.  of  10%  Na2COs  solution,  distill 
with  steam,  and  nesslerize. 

In  this  determination  care  must  be  taken  to  digest  thoroughly, 
to  add  KMn04  to  the  point  of  precipitation;  to  sample  carefully 
after  dilution,  and  to  add  enough  Na2C03  to  insure  the  separation 
of  the  NHa  from  the  precipitated  manganese  hydroxide.  KMnC>4 
must  not  be  added  during  digestion  because  it  causes  loss  of  N. 

METHOD  II. — Omit  the  separation  of  free  NHs  and  determine 
both  the  N  as  free  NHs  and  organic  N  exactly  as  described  above. 
Upon  a  separate  sample  determine  the  free  NHs  by  direct  nessler- 
ization  as  already  described.  Subtract  the  latter  to  obtain  the 
organic  N. 

NITROGEN  AS  NITRITES 

General. — The  formation  of  nitrites  is  the  second  intermediate 
step  by  which  nitrogenous  matter  passes  from  crude  organic 
matter  to  mineral  matter  (nitrates) .  Nitrites  may  be  also  formed 
by  the  reduction  of  nitrates.  The  following  is  the  standard  method 
of  procedure  for  water  and  sewages: 

Reagents. — (1)  Sulfanilic  Acid  Solution. — Dissolve  8  grams  of 
the  purest  sulfanilic  acid  in  1000  cc.  of  5  N  acetic  acid  (sp.  gr. 
1.041).  This  is  practically  a  saturated  solution. 

(2)  a-Amidonaphthalene      Acetate      Solution. — Dissolve      5.0 
grams  of  solid  a-amidonaphthalene  *  in  1000  cc.  of  5  N  acetic  acid 
and  filter  the  solution  through  washed  absorbent  cotton. 

(3)  NaN02    Stock    Solution.— Dissolve    1.1    gram  of  AgNO2 
in  nitrite-free  water;   precipitate  the  Ag  with  NaCl  solution  and 
dilute  the  whole  to  1  liter. 

(4)  Standard  NaN02   Solution. — Dilute    100   cc.   of   solution 
(3)  to  1  liter,  then  dilute  10  cc.  of  this  solution  to  1  liter  with 
sterilized  nitrite-free  water,  add  1  cc.  of  CHCls  and  preserve  in 
a  sterilized  bottle. 

1  cc.  =  0.0000001  gram  nitrogen. 

(5)  Fuchsin  Solution. — 0. 1  gram  per  liter. 

Procedure. — Measure  out  into  a  Nessler  tube  100  cc.  of  the 
decolorized  sample  (decolorized  by  adding  aluminum  hydroxide 
free  from  nitrite — see  under  Chlorine),  or  a  smaller  portion  diluted 
to  100  cc.  The  Nessler  tubes  must  be  of  clear  white  glass,  with  the 


*  a-Naphthylamine. 


MISCELLANEOUS  ANALYSES  505 

100  cc.  graduation  marks  not  varying  more  than  6  mm.  in  distance 
above  the  bottom.  At  the  same  time  make  a  set  of  standards  by 
diluting  various  volumes  of  the  standard  nitrite  solution  in  Nessler 
tubes  to  100  cc.  with  nitrite-free  water,  for  example,  0,  1,  2,  4,  7, 
10,  14,  17,  20  and  25  cc.  Add  2  cc.  of  reagents  (1)  and  (2)  above 
to  each  100  cc.  of  the  sample  and  to  each  standard.  Mix  and  let 
stand  ten  minutes.  Compare  the  samples  with  the  standards. 
Do  not  allow  the  samples  to  stand  over  one-half  hour  before  being 
compared.  Make  a  blank  determination  in  all  cases  to  correct 
for  the  presence  of  nitrite  in  the  air,  the  water,  and  the  reagents. 
Dilute  all  samples  which  develop  more  color  than  the  25  cc.  stand- 
ard before  comparing.  Mixing  is  important. 

When  100  cc.  of  the  sample  are  used,  then  0.0001  times  the 
number  of  cc.  of  the  standard  gives  the  parts  of  N  as  nitrite 
per  100,000  parts  of  water. 

NOTES. — (1)  The  solution  must  be  acid.  HC1,  which  formerly  was  in 
quite  general  use  in  this  country  as  a  solvent  for  the  naphthylamine,  permits 
satisfactory  results  to  be  obtained,  but  the  speed  of  the  reaction  is  much 
slower  than  in  the  case  of  acetic  acid.  For  this  reason  the  latter  acid  is 
preferred. 

(2)  The  nitrite  standards  made  up  as  described  above  may,  as  an  expedient 
in  routine  work,  be  matched  by  eye  by  diluting  the  fuchsin  reagent    (5)    to 
the  required  depth  of  color.     For  waters  high  in  nitrite  and  for  all  sewage 
work,  these   fuchsin   standards  have  been  found  to  be  approximate.     They 
should  be  checked  once  a  month  and  if  kept  out  of  the  bright  sunlight  are  more 
permanent  than  the  dilute  nitrite  standard. 

(3)  For  cases  not  involving  court  testimony,  the  work  can  be  considerably 
shortened  by  comparing  the  sample  with  colored  squares  of  paper  printed  on  a 
white  background  instead  of  with  the  standard  nitrite  tubes, 

NITROGEN  AS  NITRATES 

General. — No  single  method  appears  to  be  applicable  to  all 
classes  of  water  and  sewage  and  there  is  no  method  which  is  not 
subject  to  considerable  error.  Where  the  amount  of  Cl  is  less  than 
3  parts  per  100,000,  the  phenolsulfonic  acid  method  is  recom- 
mended; in  other  cases  the  reduction  method,  particularly  in 
sewage  work. 

Phenolsulfonic  Acid  Method  (for  Waters  Low  in  Cl). 

REAGENTS. — (1)  Phenolsulfonic  Acid. — Mix  30  grams  of  pure 
white  synthetic  phenol  with  370  grams  of  c.  p.  cone.  H2S04  in 
a  round-bottom  flask.  Put  this  flask  in  a  water  bath,  supported  in 


506  TECHNICAL  METHODS  OF  ANALYSIS 

such  a  way  that  it  is  completely  immersed  in  the  water,  and  heat 
for  six  hours. 

(2)  Ammonium  Hydroxide  (1  : 1). — Dilute  cone.  NtLiOH  with 
an  equal  volume  of  water.     (KOH  may  be  used.) 

(3)  Standard  Nitrate  Solution. — Dissolve  0.72   gram   of   pure 
recrystallized   KNOs   in    1   liter   of  nitrate-free   distilled  water. 
Evaporate  cautiously  10  cc.  of  this  strong  solution  to  dryness  on 
the  water  bath  in  a  porcelain  dish.     Moisten  quickly  and  thor- 
oughly with  2  cc.  of  phenolsulfonic  acid,  stirring  with  a  small  glass 
rod,  and  dilute  to  1  liter  for  the  standard  solution.     1  cc.  =  0.000001 
gram  nitrogen. 

PROCEDURE. — Evaporate  20  cc.  of  the  sample  in  a  small 
porcelain  evaporating  dish  on  the  water  bath,  removing  it  from  the 
bath  just  before  it  has  come  to  dryness.  Let  the  last  few  drops 
evaporate  at  room  temperature  in  a  place  protected  from  dust. 
When  the  sample  is  suspected  to  contain  a  large  amount  of  nitrate, 
evaporate  less  than  20  cc.  If  it  is  suspected  to  contain  but  little, 
evaporate  more.  If  the  sample  has  a  high  color,  decolorize  before 
evaporating  by  the  use  of  washed  A1(OH)3,  as  directed  under  the 
determination  of  Chlorine. 

Add  1  cc.  of  phenolsulfonic  acid  and  rub  this  quickly  and  thor- 
oughly over  the  residue  with  a  glass  rod.  Add  about  10  cc.  of 
distilled  water  and  stir  with  the  glass  rod  until  mixed.  Add 
enough  NH^OH  solution  (or  KOH  if  the  operation  must  be  carried 
on  in  a  room  where  NHs  distillations  are  made)  to  render  the 
liquid  alkaline.  Transfer  the  liquid  to  a  100  cc.  Nessler  tube  and 
fill  the  tube  to  the  100  cc.  mark  with  distilled  water. 

If  nitrates  are  present  there  will  be  formed  a  yellow  color. 
This  may  be  compared  with  permanent  standards  made  for  the 
purpose  by  putting  the  following  quantities  of  the  standard  solution 
into  100  cc.  tubes  and  making  up  to  the  100  cc.  mark  with  dis- 
tilled water,  adding  5  cc.  of  cone.  NHiOH  or  KOH  to  each  tube; 
namely,  0,  1,  2,  4,  7,  10,  15,  20,  25,  30,  35  and  40  cc.  These 
standards  may  be  kept  for  several  weeks.  Compare  the  sample 
treated  as  above  described  with  these  standards  by  looking  down 
vertically  through  the  tubes  at  a  white  surface  so  placed  in  front 
of  a  window  that  it  will  reflect  the  light  upward  through  them. 

Divide  the  figure  (cc.  of  standard)  obtained  by  this  comparison 
by  10  times  the  number  of  cc.  of  the  water  evaporated.  This  will 


MISCELLANEOUS  ANALYSES  507 

give  the  parts  of  N  in  the  form  of  nitrates  in  100,000  parts  of 
water. 

Reduction  Method  (for  Waters  and  Sewage  High  in  Cl). 
REAGENTS.— (1)  NaOH  or  KOH  Solution.— Dissolve  250  grams  of 
the  caustic  in  1250  cc.  of  distilled  water.  Add  several  strips  of  Al 
foil  and  let  the  action  proceed  overnight.  Boil  down  to  1  liter. 

(2)  Aluminum  Foil. — Use  strips  of  pure  Al  about  10  cm. 
long,  6  mm.  wide  and  0.3  mm.  thick,  and  weighing  about  0.5  gram. 

PROCEDURE. — Measure  100  cc.  of  the  sample  into  a  300  cc. 
casserole.  Add  2  cc.  of  the  caustic  solution  and  boil  down  to 
about  20  cc.  Pour  the  contents  of  the  casserole  into  a  test  tube 
about  6  cm.  long  and  3  cm.  in  diameter  and  of  about  100  cc. 
capacity.  Rinse  the  casserole  several  times  with  N-free  water 
and  add  the  rinsings  to  the  solution  already  in  the  tube,  making 
the  volume  approximately  75  cc.  Add  a  strip  of  Al  foil,  and  close 
the  tube  with  a  rubber  stopper  through  which  passes  a  glass  tube 
about  5  mm.  in  diameter,  bent  into  a  "  V."  Make  the  short  end 
of  the  tube  flush  with  the  lower  side  of  the  rubber  stopper  while  the 
other  end  extends  below  the  surface  of  distilled  water  contained 
in  another  test-tube.  This  apparatus  serves  as  a  trap  through 
which  the  evolved  hydrogen  escapes  freely.  The  amount  of  NHs 
escaping  into  the  trap  is  slight  and  may  be  neglected.  Let  the 
action  proceed  for  a  minimum  period  of  four  hours,  or  overnight. 
Pour  the  contents  of  the  tube  into  a  distilling  flask,  dilute  with 
250  cc.  of  ammonia-free  water,  distill,  collect  in  Nessler  tubes  and 
nesslerize.  When  the  nitrate  content  is  high,  collect  the  distillate 
in  a  200  cc.  flask  and  nesslerize  an  aliquot  portion.  If  the  super- 
natant liquid  in  the  reduction  tube  is  clear  and  colorless,  the  solu- 
tion may  be  diluted  to  a  definite  volume  and  an  aliquot  part 
nesslerized  without  distillation. 

OXYGEN  CONSUMED 

General. — "  Oxygen  consumed  "  means  the  oxygen  which  the 
organic  compounds  of  sewage  and  water  consume  when  treated  in 
an  acid  solution  with  KMnOi.  It  is  also  called  "  oxygen  re- 
quired "  and  "  oxygen  absorbed."  It  is  the  C  and  not  the  N  in 
organic  matter  which  is  thus  oxidized  by  KMnO4.  This  deter- 
mination is  hence  frequently  referred  to  as  an  indication  of  the 
carbonaceous  organic  matter  present.  It  indicates  only  a  certain 


508  TECHNICAL  METHODS  OF  ANALYSIS 

portion  of  the  carbon,  however,  varying  in  different  samples  of 
water  and  of  sewage.  Furthermore,  it  does  not  directly  differ- 
entiate the  C  present  in  unstable  organic  matter  from  that  which 
might  be  called  fairly  stable  organic  matter,  such  as  is  sometimes 
referred  to  as  residual  humus  matter.  If  nitrates,  ferrous  salts, 
sulfides  or  other  unoxidized  mineral  compounds  are  present,  they 
will  increase  the  O  consumed  and  a  correction  should  be  made  for 
them  when  studying  carbonaceous  organic  matter. 

The  determination  of  oxygen  consumed  is  an  empirical  pro- 
cedure and  details  must  be  strictly  followed  to  obtain  concordant 
results. 

Reagents. — (1)  Dilute  Sulfuric  Add. — One  part  of  cone. 
H2SO4  to  3  parts  of  distilled  water.  This  must  be  freed  from 
oxidizable  matters  by  adding  KMnC>4  until  a  faint  pink  color 
persists  after  standing  several  hours. 

(2)  Standard    KMnO*   Solution. — Dissolve  0.4  gram  of   the 
crystals  in  1  liter  of  distilled  water.     Standardize  against  the 
oxalate  solution.     1   cc.   is  equivalent  to  approximately  0.0001 
gram  of  available  oxygen. 

(3)  Ammonium   Oxalate   Solution. — Dissolve   0.888   gram    of 
(NH4)2C204-H2O  in   1   liter  of  distilled  water.     1   cc.  =  0.0001 
gram  of  oxygen. 

Procedure. — Measure  into  a  flask  100  cc.  of  the  water,  or  if 
high  in  organic  content,  a  similar  portion  diluted  to  100  cc.  Add 
10  cc.  of  the  H2S04  solution  and  bring  to  the  boiling  point.  Then 
add  10  cc.  of  KMnC^  solution  and  boil  for  exactly  five  minutes, 
agitating  the  liquid  constantly  with  a  small  current  of  air  to  guard 
against  bumping.  Then  immediately  add  10  cc.  of  the  ammo- 
nium oxalate  solution  and  titrate  hot  with  the  KMnC^  solution 
until  a  faint  but  distinct  pink  is  obtained.  (Accurate  10  cc. 
pipettes  should  be  used  for  measuring  the  liquids.)  Run  a  blank 
under  exactly  the  same  conditions,  using  100  cc.  of  distilled  water 
in  place  of  the  sample.  Subtract  the  KMnCU  required  by  the 
blank  from  that  required  by  the  sample.  One-tenth  the  difference 
expressed  in  cc.  gives  Oxygen  Consumed  in  parts  per  100,000. 

NOTES. — (1)  If  10  cc.  of  the  KMnO4  is  insufficient  for  complete  oxidation, 
repeat  the  determination,  using  15  cc.  or  more.  There  should  be  an  excess  of 
at  least  5  cc.  of  the  KMnO4  when  the  oxalate  is  added. 

(2)  In  connection  with  sewage  works  analysis,  the  KMnO4  solution  should 


MISCELLANEOUS  ANALYSES  509 

be  added  to  the  sample  before  heating  in  order  to  include  the  O  consumed  by 
volatile  compounds. 

(3)  If  the  sample  contains  sulfides,  nitrites,  or  ferrous  salts  in  appreciable 
quantity,  correct  the  oxygen  consumed  figure  for  the  KMnO4  reduced  by  these 
as  follows:  Digest  another  100  cc.  portion  of  the  water  with  10  cc.*  of  the 
KMnO4  at  room  temperature  for  three  minutes.  Add  about  1  cc.  of  10% 
KI  solution  (free  from  iodates),  mix  well,  and  titrate  the  liberated  iodine 
with  a  weak  thiosulfate  solution  (1.0  gram  per  liter).  Run  a  blank  on  10  cc. 
of  the  KMnO4  and  100  cc.  of  distilled  water  in  the  same  way  to  establish 
the  relation  between  the  KMnO4  and  the  thiosulfate  solution.  The  amount  of 
KMnC>4  consumed  by  the  100  cc.  of  sample  in  the  cold  should  be  subtracted 
from  the  amount  consumed  hot,  before  calculating  the  Oxygen  Consumed 

CHLORINE 

General. — Chlorine  in  waters  and  sewages  has  its  origin  for  the 
most  part  in  the  common  salt,  which  comes,  generally  speaking, 
from  mineral  deposits  in  the  earth,  from  the  ocean  vapors  carried 
inland  by  the  wind,  or  from  polluting  materials  like  sewage  and 
trade  wastes,  which  contain  the  salt  used  in  the  household  and  in 
manufacturing.  Comparison  of  the  chlorine  content  of  a  water 
with  that  of  other  waters  in  the  general  vicinity  known  to  be 
unpolluted,  frequently  affords  useful  information  as  to  its  sanitary 
quality. 

Reagents. — (1)  Standard  Salt  Solution. — Dissolve  16.50  grams 
of  fused  NaCl  in  distilled  water  and  dilute  to  1  liter.  Dilute  100  cc. 
of  this  stock  solution  to  1  liter  in  order  to  obtain  a  standard  solu- 
tion, each  cc.  of  which  contains  0.001  gram  of  Cl. 

(2)  Standard    AgNOs.— Dissolve    2.396    grams    of    AgN03 
crystals  in  1  liter  of  distilled  water.     One  cc.  of  this  will  be  equiva- 
lent  to   approximately    0.0005    gram   of   chlorine.     Standardize 
against  the  standard  salt  solution. 

(3)  Potassium    Chromate  Indicator. — Dissolve    50    grams    of 
neutral  K^CrCU  in  a  little  distilled  water.     Add  enough  AgNOs 
to  produce  a  slight  red  precipitate.     Filter  and  make  up  the 
filtrate  to  1  liter  with  distilled  water. 

(4)  Aluminum  Hydroxide. — Dissolve  125  grams  of  potash  alum 
or  ammonia  alum  in  1  liter  of  distilled    water.     Precipitate  the 
A1(OH)3  by  cautiously  adding  NH4OH.     Wash  the  precipitate 
in  a  large  jar  by  the  successive  addition  of  distilled  water  and  by 
decantation  until  free  from  Cl,  nitrites  and  NH3. 

*  Or  more  if  necessary.    See  Note  (1). 


510  TECHNICAL  METHODS  OF  ANALYSIS 

Procedure. — Use  50  or  100  cc.  of  the  sample  in  a  white  6-inch 
porcelain  evaporating  dish,  where  the  Cl  is  not  extremely  low  or 
very  high.  If  the  Cl  is  very  high,  use  25  cc.  (or  even  a  smaller 
quantity)  diluting  the  volume  taken  to  50  cc.  with  distilled  water. 
A  satisfactory  end-point  cannot  be  obtained  when  more  than 
8-10  cc.  of  the  AgNOs  solution  are  required.  When  there  are 
over  100  parts  of  Cl  per  100,000,  a  gravimetric  determination 
should  be  made. 

When  the  sample  is  very  low  in  Cl  more  accurate  results  may 
be  obtained  by  using  50  or  100  cc.  of  the  sample  and  adding, 
prior  to  titration,  1  cc.  of  standard  NaCl  solution,  correcting 
for  this  in  the  calculation. 

If  the  sample  has  a  color  greater  than  about  30,  it  must  be 
decolorized  by  heating  it  to  the  boiling  point  with  washed  Al(OH)a 
(3  cc.  to  500  cc.  of  the  sample).  Make  the  determination  on  a 
portion  of  the  clarified  sample,  filtered,  if  necessary. 

Before  titrating  the  Cl  add  2  or  3  drops  of  phenolphthalein 
indicator.  If  a  red  color  appears,  neutralize  with  approximately 
0.1  or  0.05  N  H2SO4.  If  the  water  is  acid  to  methyl  orange  add  a 
slight  excess  of  pure  CaCOs  (or  just  neutralize  with  0.1  or  0.05  N 
Na2C03). 

Rotate  the  neutral  liquid  in  the  dish  to  make  sure  that  no  por- 
tion of  any  residue  on  the  side  walls  remains  undissolved,  rubbing 
if  necessary  with  a  rubber-tipped  glass  rod.  Add  1  cc.  of  the 
K2Cr04  indicator  and  titrate  with  the  AgNOs  solution,  under 
similar  conditions  as  to  volume,  light  and  temperature  as  were 
used  in  standardizing  the  AgNOs.  The  detection  of  the  end- 
point  is  facilitated  by  frequent  comparison  of  the  contents  of  the 
porcelain  dish  in  which  the  determination  is  being  made  with  those 
of  another  dish  placed  alongside  and  containing  the  same  quantity 
of  chromate  solution  in  the  same  volume  of  distilled  water  as  the 
volume  of  the  sample  taken  for  titration.  It  is  also  preferable 
to  make  the  titrations  in  a  darkened  room  provided  with  a  yellow 
light. 

HARDNESS 

General. — The  hardness  of  water  is  caused  chiefly  by  the  salts 
of  Ca  and  of  Mg.  It  is  commonly  measured  by  the  soap-destroying 
power  of  the  water.  The  addition  of  K  or  Na  soap  causes  its 


MISCELLANEOUS  ANALYSES  511 

decomposition  and  produces  insoluble  Ca  and  Mg  soaps.  The 
solubility  of  carbonates  of  Mg  and  Ca  in  a  water  beyond  certain 
limits  depends  upon  the  presence  of  CO2  and  results  in  bicarbonates. 
On  boiling  the  CC>2  is  removed  and  the  normal  carbonates  pre- 
cipitated. Precipitation,  however,  is  not  complete,  as  the  normal 
carbonates  themselves  have  a  slight  solubility.  The  hardness  of 
the  water  removed  by  boiling  is  called  "  temporary  hardness. " 
The  hardness  which  still  remains  is  termed  "  permanent  hardness," 
and  is  due  largely  to  sulfates  and  chlorides  of  Ca  and  Mg  and 
to  the  traces  of  carbonates  still  held  in  solution. 

It  is  generally  sufficient  to  determine  the  total  hardness  of  the 
water.  In  case  the  permanent  hardness  is  also  desired,  boil 
gently  a  known  volume  of  the  water  for  one-half  hour,  let  cool,  and 
then  restore  to  its  original  volume  with  recently  boiled  and  cooled 
distilled  water.  Then  filter  the  water  and  determine  the  per- 
manent hardness  in  the  filtrate  by  the  soap  method  as  below. 
This,  subtracted  from  the  total  hardness,  will  give  the  temporary 
hardness. 

Total  Hardness  by  the  Soap  Method. — REAGENTS. — (1)  Stand- 
ard CaCk  Solution. — Dissolve  0.2  gram  of  pure  calcite  (CaCOs) 
in  a  little  dil.  HC1,  being  careful  to  avoid  loss  of  solution  by  spatter- 
ing. Evaporate  to  dryness  several  times  to  expel  excess  of  acid, 
dissolve  in  distilled  water  and  make  up  to  1  liter.  1  cc.  =  0.0002 
gram  CaCOs. 

(2)  Standard  Soap  Solution. — Dissolve  100  grams  of  dry  white 
castile  soap  in  1  liter  of  80%  alcohol  and  let  stand  several  days 
before  standardizing.  From  the  above  stock  solution  dilute  with 
70%  alcohol  such  a  quantity  that  the  resulting  diluted  soap  solution 
will  give  a  permanent  lather  when  6.40  cc.  of  it  are  properly  added 
to  20  cc.  of  standard  CaCb  solution.  Usually  from  75-100  cc. 
of  the  stock  soap  solution  are  required  for  making  1  liter  of  the 
standard  soap  solution.  Pure  potassium  oleate,  made  from  lead 
plaster  and  K^COs,  may  be  used  to  advantage  in  place  of  castile 


STANDARDIZATION. — Pipette  20  cc.  of  the  CaC]2  solution  into  a 
250  cc.  glass-stoppered  bottle  and  dilute  to  50  cc.  with  distilled 
water  which  has  been  recently  boiled  and  cooled.  Then  add  from 
a  burette  0.2-0.3  cc.  of  soap  solution  at  a  time,  shaking  the  bottle 
vigorously  after  each  addition  until  a  lather  over  the  entire  surface 


512 


TECHNICAL  METHODS  OF  ANALYSIS 


of  the  water  is  formed,  which  remains  continuous  for  five  minutes 
after  the  bottle  is  laid  upon  its  side.  When  the  soap  solution  is  of 
the  strength  above  stated,  then  the  quantity  of  CaC03  equivalent 
to  each  cc.  of  the  soap  solution  is  indicated  in  the  following  table: 

TABLE  OF  HARDNESS  SHOWING  THE  PARTS  OF  CaCO3  PER  100,000  FOR  EACH 
0.1  cc.  OF  SOAP  SOLUTION  WHEN  50  cc.  OF  THE  SAMPLE  ARE  USED. 


Soap 
Solution 

0.0 

0.1 

0.2 

0.3 

0.4 

0.5 

0.6 

0.7 

0.8 

0.9 

cc. 

cc. 

cc. 

cc. 

cc. 

cc. 

cc. 

cc. 

cc. 

cc. 

cc. 

0.0 

0.0 

0.16 

0.32 

1.0 

0.48 

0.63 

0.79 

0.95 

1.11 

1.27 

1.43 

1.56 

1.69 

1.82 

2.0 

1.95 

2.08 

2.21 

2.34 

2.47 

2.60 

2.73 

2.86 

2.99 

3.12 

3.0 

3.25 

3.38 

3.51 

3.64 

3.77 

3.80 

4.03 

4.16 

4.29 

4.43 

4.0 

4.57 

4.71 

4.86 

5.00 

5.14 

5.29 

5.43 

5.57 

5.71 

5.86 

5.0 

6.00 

6.14 

6.29 

6.43 

6.57 

6.71 

6.86 

7.00 

7.14 

7.29 

6.0 

7.43 

7.57 

7.71 

7.86 

8.00 

8.14 

8.29 

8.43 

8.57 

8.71 

7.0 

8.86 

9.00 

9.14 

9.29 

9.43 

9.57 

9.71 

9.86 

10.00 

10.15 

PROCEDURE. — Measure  50  cc.  of  the  water  into  a  250  cc.  bottle 
and  add  soap  solution  in  small  quantities  and  in  precisely  the  same 
manner  as  described  under  the  standardization  of  the  soap  solution. 
From  the  result  obtained,  calculate  from  the  table  above  the  total 
hardness  of  the  water,  expressed  as  parts  of  CaCOs  per  100,000. 

When  adding  the  soap  solution  to  waters  containing  Mg  salts, 
it  is  necessary  to  avoid  mistaking  the  false  end-point  *  for  the  true 
one.  Consequently,  after  the  titration  is  apparently  finished, 
read  the  burette  and  add  about  0.5  cc.  more  of  soap  solution.  If 
the  end-point  was  due  to  Mg,  the  lather  now  disappears.  Soap 
solution  must  then  be  added  until  the  true  end-point  is  reached. 
Usually  the  false  lather  persists  for  less  than  five  minutes. 

When  more  than  7  cc.  of  soap  solution  are  required  for  50  cc. 
of  the  water,  it  is  necessary  to  take  less  of  the  sample  and  dilute 
to  50  cc.  with  distilled  water  which  has  been  recently  boiled  and 
cooled.  This  step  reduces  somewhat  the  disturbing  influence  of 
Mg  salts,  which  consume  more  soap  than  do  equivalent  weights  of 
*  Also  called  the  Magnesium  end-point. 


MISCELLANEOUS  ANALYSES  513 

Ca  salts.  At  best  the  soap  method  is  not  a  precise  test  on  account 
of  the  varying  amounts  of  Ca  and  Mg  present  in  different  waters. 
For  hard  waters,  especially  in  connection  with  processes  for  puri- 
fication and  softening,  it  is  advisable  not  to  use  this  method  but 
to  calculate  the  total  hardness  (in  terms  of  CaCOs)  from  the 
amount  of  CaO  and  MgO  found  by  chemical  analysis. 

NOTES. — (1)  When  free  CO2  is  present  in  the  sample  in  considerable 
amount,  it  should  be  removed  by  aeration. 

(2)  The  strength  of  the  soap  solution  should  be  determined  from  time  to 
time,  to  make  sure  that  it  has  not  materially  changed  while  standing.     Unless 
otherwise  stated,  record  all  results  in  terms  of  CaCO3. 

(3)  English  degrees  of  hardness,  Clark's  scale,  are  equivalent  to  grains  of 
CaCO3  per  imperial  gallon,  and  are  multiplied  by  1.43  to  give  parts  per 
100,000. 

(4)  French  degrees  of  hardness  represent  parts  of  CaCO3  per  100,000,  and 
are  the  same  as  obtained  by  the  above  table. 

(5)  German  degrees  of  hardness  represent  parts  of  CaO  per  100,000  and 
are  multiplied  by  1.78  to  give  parts  of  CaCO3  per  100,000. 

IRON 

General. — Iron  in  ground  waters  is  usually  in  the  soluble  fer- 
rous state,  sometimes  as  carbonate  or  sulfate  and  also  combined 
as  organic  matter.  Most  waters,  especially  those  which  have  been 
exposed  to  the  air,  contain  the  iron  in  the  form  of  a  colloidal 
hydroxide. 

Total  Iron. — REAGENTS. — (1)  Standard  Fe  Solution. — Dissolve 
0.7  gram  of  Fe(NH4)2(S04)2-6H20  in  50  cc.  of  distilled  water  and 
add  20  cc.  of  dil.  H2S04.  Warm  slightly  and  add  KMnO4,  little 
by  little,  until  the  Fe  is  completely  oxidized.  Dilute  to  1  liter. 
1  cc.  =  0.0001  gramFe. 

(2)  KSCN  Solution.— Dissolve  20  grams  in  1  liter  of  distilled 
water. 

(3)  Dilute  HCl.—Md  to  cone.  HC1  (free  from  HN03)  an  equal 
volume  of  distilled  water. 

(4)  0.2N  KMnO±. — Dissolve    6.30  grams    in   distilled  water 
and  dilute  to  a  liter. 

(5)  Cone.  HCl. — Free  from  iron. 

PROCEDURE. — Evaporate  100  cc.  of  the  sample  to  dryness. 
(Use  the  residue  from  the  total  solids  determination,  if  convenient.) 
If  it  contains  much  organic  matter  destroy  this  by  gentle  ignition. 


514  TECHNICAL  METHODS  OF  ANALYSIS 

Cool  and  add  5  cc.  of  cone.  HC1,*  moistening  the  whole  of  the 
inner  surface  of  the  dish.  Warm  for  two  to  three  minutes  and 
again  moisten  the  whole  inner  surface  with  acid.  Rinse  down  the 
sides  of  the  dish  with  5-10  cc.  of  distilled  water  and  let  stand  on  the 
water  bath  for  about  three  minutes.  Wash  the  hot  acid  solution 
into  a  100  cc.  Nessler  tube.  Filter  the  sample  if  necessary,  first 
washing  the  filter  paper  with  hot  water.  Add  a  drop  or  two  of 
KMn04  solution  to  be  sure  that  the  Fe  is  oxidized.  The  pink 
color  should  persist  for  at  least  five  minutes.  If  not,  add  more, 
a  drop  at  a  time. 

To  the  cooled  solution  add  10  cc.  of  KSCN  solution,  dilute  to 
100  cc.  and  mix  thoroughly.  Compare  the  color  immediately 
with  a  series  of  standards,  prepared  side  by  side  with  the  sample 
in  100  cc.  Nessler  tubes.  These  standards  should  be  prepared 
from  the  standard  Fe  solution,  containing  amounts  ranging  from 
0.5-4.0  cc.  of  the  latter.  Dilute  these  amounts  with  distilled 
water  to  about  50  cc.  Add  5  cc.  of  cone.  HC1  and  a  drop  or  two 
of  KMnO4  and  then  10  cc.  of  KSCN  solution.  Finally  dilute  all  the 
standards  to  100  cc. 

NOTE. — For  a  single  sample,  it  is  more  convenient  to  run  standard  Fe  solu- 
tion from  a  burette  into  a  Nessler  tube  containing  the  acid,  distilled  water  and 
KSCN,  until,  after  mixing,  the  color  matches  the  sample.  From  the  reading 
of  the  burette,  calculate  the  amount  of  Fe.  When  using  standards,  the  color 
comparisons  must  be  made  immediately. 

REFERENCES. — American  Public  Health  Association,  "  Standard  Methods 
of  Water  Analysis,"  1913.  J.  Assoc.  Official  Agr.  Chemists,  Methods  of 
Analysis  (1916-17),  pages  35-39, 

INDUSTRIAL  WATER 

General. — This  method  applies  to  the  mineral  analysis  of 
waters  to  be  used  for  boilers  and  for  general  manufacturing  pur- 
poses. It  is  fully  realized  that  it  is  open  to  criticism  from  a  strictly 
chemical  standpoint  (e.g.,  it  takes  no  account  of  the  possible 
presence  of  potassium  salts  or  bicarbonates)  but  the  results  give  the 
desired  information  for  practically  all  technical  purposes. 

The  quantity  of  water  which  must  be  taken  for  analysis 
depends  upon  the  amount  of  dissolved  solids  which  it  contains. 
As  a  general  rule,  about  1  liter  is  a  suitable  amount  of  water  for 
*  Dilute  HC1  will  not  dissolve  all  the  Fe2O3. 


MISCELLANEOUS  ANALYSES  515 

evaporation.  One  U.  S.  gallon  of  pure  water  at  60°  F.  contains 
58,334.9  grains.  If,  therefore,  583.3  cc.  of  water  are  taken  for 
analysis,  the  weight  in  centigrams  of  the  various  substances  found 
will  give  directly  the  number  of  grains  per  U.  S.  gallon.  For 
ordinary  waters,  therefore,  evaporate  1167  cc.  and  divide  by  2 
the  number  of  centigrams  obtained.  The  results  will  be  grains 
per  gallon. 

It  is  convenient  to  have  several  flasks  specially  calibrated  to 
contain  1167  cc.,  583.3  cc.,  291.7  cc.  and  116.7  cc.,  respectively. 
These  may  be  prepared  by  selecting  ordinary  volumetric  flasks 
of  1000  cc.,  500  cc.,  250  cc.  and  100  cc.,  respectively,  choosing 
flasks  where  the  graduation  mark  is  low  on  the  neck.  Weigh  each 
flask,  place  in  it  the  proper  number  of  grams  of  water  at  20°  C. 
and  make  a  new  mark  at  the  meniscus  of  the  water;  or,  fill  each 
to  its  original  mark,  add  the  proper  number  of  cc.  of  water  from  a 
burette  to  bring  the  volume  to  the  proper  figure,  and  make  the  new 
mark,  preferably  by  etching.  A  suitable  flask  for  the  largest  size 
is  the  kind  with  a  bulb  in  the  neck  and  2  graduations  at  1000  and 
1100  cc. 

If  1000  cc.  are  taken  for  analysis,  multiply  the  number  of  cen- 
tigrams found  by  0.5833  to  obtain  grains  per  gallon. 

Free  Carbon  Dioxide. — To  291.7  cc.  of  the  sample  (measured 
in  a  specially  graduated  flask)  contained  in  a  400  cc.  Erlenmeyer 
flask  add  1  cc.  of  phenolphthalein  indicator  solution,  and  titrate 
rapidly  with  0.01  N  Na2COs  till  a  faint  pink  color  persists  after 
gentle  shaking.  Take  care  not  to  breathe  into  the  flask  and  do 
not  use  a  flask  unnecessarily  large.  Calculate  the  titration  to 
CO2,  according  to  the  reaction 

Na2CO3 + C02 + H2O  =  2NaHC03. 

CALCULATION.— 1  cc.  0.01  N  Na2CO3  =  0.00022  gram  C02. 
Multiply  by  2  the  number  of  centigrams  of  CO2  obtained  and 
the  result  will  be  grains  per  U.  S.  gallon. 

NOTE. — If  the  sample  contains  over  46  grains  of  NaHCO3  per  gallon  or  if 
the  total  carbonate  hardness  is  over  10  (corresponding  to  the  equivalent  of 
5.8  grains  of  CaCOs  per  gallon)  it  must  be  diluted  with  CCVfree  water  before 
titration,  to  prevent  the  precipitation  of  CaCO3  and  MgCO3  with  consequent 
liberation  of  COa. 


516  TECHNICAL  METHODS  OF  ANALYSIS 

Suspended  Matter. — If  the  sample  is  decidedly  turbid  or 
contains  an  appreciable  amount  of  suspended  matter,  shake 
thoroughly  and  measure  out  1167  cc.  in  a  specially  graduated  flask. 
Filter  through  a  filter  paper*  which  has  previously  been  dried  at 
100°  C.  and  weighed  in  a  weighing  bottle,  collecting  the  clear 
filtrate  in  a  clean  beaker  or  flask.  Wash  the  residue  on  the  filter 
paper  once  with  distilled  water  and  dry  at  100°  C.  in  the  same 
weighing  bottle.  Cool  in  a  desiccator  and  weigh.  Divide  by 
2  the  number  of  centigrams  to  obtain  the  grains  of  total  suspended 
matter  per  gallon. 

Ignite  the  filter  paper  in  a  weighed  platinum  crucible,  dry  in  a 
desiccator  and  weigh.  This  weight  will  give  the  amount  of  non- 
volatile suspended  matter. 

Total  Solids. — Evaporate  the  filtrate  obtained  above  in  a 
weighed  platinum  dish  on  the  steam  bath.  Finally  dry  in  the 
steam  oven  at  100°  C.  for  about  one-half  hour.  Cool  in  a  desic- 
cator and  weigh. 

NOTE. — The  evaporation  may  be  hurried  by  gentle  boiling  on  a  hot  plate  or 
over  a  free  flame  on  an  asbestos  mat,  taking  care  not  to  lose  any  by  spattering 
and  not  to  let  it  go  to  dryness  before  transferring  to  the  steam  bath.  In  urgent 
cases  clamp  a  horizontal  glass  tube  about  0.5  inch  above  the  top  of  the  dish, 
with  the  open  end  at  about  the  center,  and  connect  the  other  end  to  suction 
or  a  gentle  air  blast  to  remove  the  vapors. 

Organic  and  Volatile  Matter. — Manipulate  the  dish  in  a  Tirrill 
flame  with  a  pair  of  tongs  until  the  organic  matter  is  burned  off  at 
as  low  a  temperature  as  possible.  Cool  in  a  desiccator  and  weigh. 
Report  the  loss  as  "  organic  and  volatile  matter." 

NOTE. — This  result  will  generally  be  too  high,  due  to  loss  of  CO2  from  car- 
bonates, and  is  used  only  as  a  rough  check  on  the  analysis,  the  actual  organic 
and  volatile  matter  in  the  final  calculation  being  taken  "by  difference." 

Total  Mineral  Matter  as  Sulfates. — Add  a  few  drops  of  dil. 
H2S04  to  the  above  residue  in  the  platinum  dish  (note  here 
whether  there  is  an  effervescence  of  carbonates).  Manipulate  the 
dish  so  that  the  acid  will  come  in  contact  with  all  of  the  residue. 

*A  Gooch  crucible  may  be  used  if  preferred,  although,  if  the  water  con- 
tains much  organic  matter  or  fine  silt,  these  may  have  a  tendency  to  clog  the 
asbestos  mat. 


MISCELLANEOUS  ANALYSES  517 

If  there  is  a  strong  effervescence,  it  will  be  advisable  to  add  a  few 
more  drops  of  the  acid. 

Evaporate  to  dryness  on  the  steam  bath  and  then  to  fumes  of 
S03  on  the  hot  plate.  (If  no  white  fumes  are  obtained,  insufficient 
H2S04  has  been  added.)  Finish  the  heating  carefully  over  a 
free  flame  until  the  evolution  of  S03  fumes  ceases.  Then  heat 
for  some  time  at  a  red  heat  to  decompose  any  FeSO4  into  Fe203. 
Cool  in  a  desiccator  and  weigh.  The  combined  weight  represents 
the  mineral  matter  as  Fe2O3,  SiO2,  A1203,  CaSO4,  MgSC>4  and 
alkaline  sulfates.  For  all  ordinary  purposes  the  latter  may  be 
considered  Na2S04. 

Silica. — Add  a  few  cc.  of  cone.  HC1  to  the  above  residue  and 
warm  until  all  the  Fe2O3  dissolves.  Dilute  with  about  twice  the 
volume  of  water  and  continue  the  heating  for  a  short  time.  During 
the  heating  loosen  the  insoluble  matter  adhering  to  the  dish  with 
a  rubber  policeman  and  stir  to  hasten  the  solution.  Filter  through 
a  small  ashless  filter  and  wash  the  residue  with  hot  water.  Place 
the  filter  paper  containing  the  insoluble  matter  in  the  original 
platinum  dish  and  burn  off  the  filter  paper,  taking  care  to  protect 
the  dish  from  drafts  of  air.  Cool  in  a  desiccator  and  weigh  as  SiC>2. 

NOTE. — If  the  water  is  to  be  used  for  boiler  purposes,  it  is  not  necessary 
to  determine  the  silica  separately  unless  a  large  amount  is  present. 

Iron  Oxide  and  Alumina. — Heat  the  filtrate  from  the  Si02 
(or,  in  case  the  SiO2  is  not  to  be  determined  separately,  the  unfil- 
tered  solution  of  the  .sulfates)  nearly  to  boiling.  Add  a  slight 
excess  of  NEUOH  and  digest  on  the  steam  bath  until  the  odor  of 
NH3  is  nearly  gone.  Filter  through  a  small  filter.  Ignite  strongly 
in  a  platinum  crucible,  cool  in  a  desiccator  and  weigh  as 
Fe203+Al203(+Si02). 

NOTE. — If  Mn  is  suspected  to  be  present,  add  5  cc.  of  strong  bromine  water 
and  boil  before  adding  the  NH4OH  to  precipitate  iron  and  alumina.  In  this 
case  the  Mn  will  come  down  with  the  iron  and  alumina  after  treatment  with 
bromine  water  and  NH^OH  and  if  it  is  desired  to  know  the  amount,  it  must  be 
determined  in  a  separate  portion  of  the  water  and  the  amount  (calculated 
as  Mn3O4)  subtracted  from  the  total  weight  of  the  NH4OH  precipitate.  (See 
pages  110  and  148,  under  Manganese.) 

Iron  Oxide. — If  it  is  desired  to  determine  the  Fe2O3  separately, 
fuse  the  residue  in  the  crucible  with  a  little  KHS04.  Dissolve  the 


518  TECHNICAL  METHODS  OF  ANALYSIS 

fusion  in  water  and  determine  the  Fe20s  colorimetrically  with 
KSCN,  matching  the  color  against  a  standard  Fe  solution.  (See 
under  Total  Iron  on  page  513.) 

Alumina. — Ordinarily  A12O3  is  not  determined  separately.  If, 
however,  the  colorimetric  determination  of  Fe  leaves  considerable 
to  be  accounted  for  in  the  NH^OH  precipitate,  the  difference  may 
be  considered  as  A^Os. 

Lime. — Heat  to  boiling  the  filtrate  from  the  NH^OH  precipitate. 
Add  5  cc.  of  (NEU) 20264  reagent  solution  and  digest  on  the  steam 
bath  until  the  precipitate  has  settled.  Filter  through  a  small 
ashless  filter,  wash  well  with  hot  water,  ignite  thoroughly  in  a 
platinum  crucible  and  weigh  as  CaO. 

NOTE. — Instead  of  igniting  the  CaC2O4  it  may  be  titrated  with  0.1  N 
KMnO4  as  follows: 

In  a  400  cc.  beaker  place  about  125  cc.  of  distilled  water  and  add  5-7  cc 
of  cone.  H2SO4.  Drop  the  moist  filter  paper  containing  the  CaC2O4  into  this. 
and  heat  to  about  70°  C.  Stir  to  effect  the  decomposition  of  the  CaC2O4 
but  avoid  excessive  disintegration  of  the  paper.  Titrate  the  hot  solution, 
with  constant  stirring,  with  0.1  N  or  0.01  N  KMnO4  until  a  permanent  pink 
color  forms. 

CALCULATION.— 1  cc.  0.1  N  KMnO4  =  0.002804  gram  CaO. 

Magnesia. — Make  the  filtrate  from  the  CaO  determination 
slightly  acid  with  HC1  and  evaporate  until  crystallization  starts. 
Dissolve  any  crystals  formed  with  a  small  amount  of  distilled 
water.  Cool,  and  add  25  cc.  of  a  10%  solution  of  (NH^HPO^ 
(It  is  permissible  to  use  Na2HPO4  or  NaNH4HP04.)  Then  add 
slowly  with  constant  stirring  cone.  NELjOH  until  neutral,  finally 
adding  about  2  cc.  in  excess.  This  is  best  done  from  a  burette 
or  a  Mohr  pipette.  Let  stand  overnight,  if  possible,  or  cool  in 
ice  water  and  stir  for  one-half  hour.  Filter  through  a  weighed 
Gooch  crucible  and  wash  with  magnesia  wash  solution.*  Dry 
the  precipitate  and  then  finally  ignite  strongly,  cool  and  weigh  as 
Mg2P207.  Calculate  to  MgO. 

CALCULATION.— Mg2P2O7X  0.3621  =  MgO. 

Alkalies. — For  all  ordinary  purposes  the  alkalies  may  be 
regarded  as  consisting  wholly  of  Na2O  and  are  obtained  by  cal- 
culation as  described  below. 

*Magnesia  wash  solution:  Add  200  grams  of  NH4N03  to  400  cc.  of  cone. 
NH4OH;  mix  and  dilute  with  water  to  1  liter. 


MISCELLANEOUS  ANALYSES  519 

Sulfur  Trioxide. — To  291.7  cc.  of  the  sample  (measured  in  a 
specially  graduated  flask),  contained  in  a  400  cc.  beaker,  add  5  cc. 
of  dil.  HC1.  Heat  to  boiling  and  then  add,  drop  by  drop,  5  cc.  of 
10%  BaCb  solution.  Let  stand  overnight,  protected  from  SO3 
fumes.  Filter,  wash  with  hot  water,  ignite  the  precipitate  and 
weigh  as  BaS04.  Calculate  to  SO3  and  multiply  the  number  of 
centigrams  of  SO3  by  2  to  obtain  grains  per  gallon. 

CALCULATION.— BaSO4  X  0.3430  =  SO3. 

Chlorine. — Determine  chlorine  by  the  procedure  given  on 
page  509.  If  116.7  cc.  of  the  water  are  used,  then  the  number 
of  cc.  of  the  standard  AgN03  solution,  divided  by  4,  will  give 
directly  grains  of  Cl  per  U.  S.  gallon. 

If  the  water  contains  over  60  grains  of  Cl,  make  the  determi- 
nation gravimetrically,  weighing  the  AgCl. 

Calculation  of  Results.— Calculate  the  CaO  and  MgO  to  CaSO4 
and  MgSO4,  respectively.  Add  to  the  sum  of  these  the  amount  of 
Fe2O3,  SiC>2  and  A^Os  and  subtract  this  sum  from  the  total  weight 
of  mineral  matter  calculated  as  sulfates,  as  previously  determined. 
Consider  the  difference  as  Na2S04  and  calculate  the  equivalent 
amount  of  Na20. 

Calculate  the  total  Cl  to  NaCl,  if  there  is  enough  Na2O  to 
combine  with  it.  If,  however,  there  is  an  excess  of  Cl  over  the 
Na2O,  calculate  the  remainder  to  MgCl2.  If  the  Na2O  is  in  excess 
of  the  Cl,  calculate  the  excess  to  Na2SO4  and  then  the  remainder, 
if  any,  to  Na2C03.  If  there  is  insufficient  Na2O  left  from  NaCl 
to  combine  with  all  the  SOs,  calculate  the  excess  of  the  latter  to 
CaSO4.  If  the  SO3  is  still  in  excess,  combine  it  with  any  MgO  not 
satisfied  with  Cl,  and  if  there  is  still  an  excess,  calculate  it  to  H2SO4. 
(In  this  case,  of  course,  the  water  would  show  an  acid  reaction  to 
methyl  orange  and  litmus.)  Calculate  any  MgO  or  CaO  not 
accounted  for  by  Cl  and  SOs  to  CaCO3  and  MgCO3,  respectively. 
If  the  Na2O  is  in  excess  of  both  Cl  and  SO3,  calculate  the  excess  to 
Na2C03.  The  Fe2O3  is  probably  present  as  FeSO4  but  for  practical 
purposes  this  calculation  is  unnecessary.  The  SiO2  is  usually 
reported  as  such,  although  in  water  containing  a  considerable 
amount,  and  also  containing  Na2CO3,*  it  may  be  present  as  sodium 
silicate. 

*  Water  containing  Na2CO3  will  be  alkaline  to  phenolphthalein,  although, 
even  if  the  water  is  neutral  to  this  indicator,  it  may  still  contain  NaHCO3,  in 
which  case  it  will  be  alkaline  to  methyl  orange. 


520  TECHNICAL  METHODS  OF  ANALYSIS 

Report  the  final  results  as  follows : 

Grains  per 
U.  S.  gallon 

Free  Carbon  Dioxide  (CO2) 

Suspended  Matter: 

Organic  and  Volatile 

Non-volatile 

Total 

On  Filtered  Sample 

Silica  (SiO2) 

Alumina  (A12O3) 

Iron  Oxide  (Fe2O3) 

Lime  (CaO) 

Magnesia  (MgO) 

Sodium  Oxide  (Na2O) 

Sulfur  Trioxide  (SO3) 

Chlorine  (Cl) . 


Probably  combined  as  follows: 

Silica  (SiO2) 

Iron  Oxide  (Fe2O3) 

Alumina  ( A12O3) 

Sodium  Chloride  (NaCl) 

Sodium  Sulfate  (Na2SO4) 

Sodium  Carbonate  (Na2CO3) .... 
Magnesium  Chloride  (MgCl2) .  . . 
Magnesium  Sulfate  (MgSO4) .... 
Magnesium  Carbonate  (MgCO3) . 

Calcium  Chloride  (CaCl2) 

'  Calcium  Sulfate  (CaSO4) 

Calcium  Carbonate  (CaCO3) 

Residue  on  Evaporation 


NOTES. — (1)  In  waters  which  are  to  be  used  for  boiler  purposes  it  is  suf- 
ficient ordinarily  to  report  Fe2O3,  A12O3  and  SiO2  together,  and  not  separately. 

(2)  The  following  are  incrusting  or  scale-forming  solids : 

Oxides  of  iron  and  aluminum. 

Calcium  sulfate  and  carbonate. 

Calcium  chloride  (corrosive). 

Magnesium  sulfate  (forms  scale  only  in  the  presence  of  CaCO3). 

Magnesium  chloride  (strongly  corrosive). 

Magnesium  carbonate. 
The  following  are  non-incrusting  solids: 

Chlorides,  sulfates  and  carbonates  of  the  alkalies. 

Organic  matter. 


MISCELLANEOUS  ANALYSES 


521 


(3)  The  general  grading  of  waters  for  boiler  purposes,  according  to  the 
contents  of  scale-forming  matter  is  as  follows: 


10-20  grains  Fair 

20-30  grains                                                                    Poor 

30-40  grains  Bad 

Over  40  grains  Very  bad 

(4)  Grains  per  gallon  X-V°-=lbs-  Per  10,000  gallons. 

Factors.  —  The  following  factors  will  be  found  useful  in  cal- 

culating results: 

Given 

i 
Wanted 

Factor 

Log 

CaCl2 

CaO 

0.5052 

9.70346 

CaO 

CaCO3 

1.7849 

0.25161 

CaS04 

2.4279 

0.38523 

CaS04 

CaO 

0.4119 

9.61479 

Cl 

CaCl2 

1.5650 

0.19451 

KC1 

2.1025 

0.32274 

MgCl2 

1.3429 

0.12805 

NaCl 

1.6486 

0.21712 

CO2 

NaaCO, 

2.4090 

0.38184 

Fe203 

FeCO3 

1.4510 

C.  16167 

KC1 

K2O 

0.6317 

9.80050 

K2SO4 

1  .  1686 

0.06766 

K2O 

K2CO3 

1.4671 

0.16647 

K2SO4 

1.8499 

0.26715 

MgCl2 

MgO 

0.4234 

9.62675 

MgO 

MgC03 

2.0915 

0.32046 

MgS04 

2.9857 

0.47504 

Mn3O4 

MnCO3 

1.5071 

0.17814 

NaCl 

Cl 

0.6066 

9.78290 

Na20 

0.5303 

9.72452 

522 


TECHNICAL  METHODS  OF  ANALYSIS 


Given 

Wanted 

Factor 

Log 

Na2CO3 

Na2SO4 

1  .  3401 

0.12713 

Na2O 

NaCl 
Na2CO3 

Na2Si03 
Na2SO4 

1.8858 
1.7098 
1.9726 
2.2913 

0.27550 
0.23295 
0.29504 
0.36008 

Na2S04 

Na2CO3 
Na2O 
S03 

0.7462 
0.4364 
0  5636 

9.87286 
9  .  63989 
9.75097 

Si02 

C02* 

Na2SiO3 

0.7298 
2.0282 

9.86320 
0.30711 

S03 

CaSO4 
MgS04 
Na2SO4 

1.7004 
1.5036 
1.7744 

0.23055 
0.17712 
0.24905 

REFERENCES. — Low:    "Technical   Methods  of  Ore  Analysis."     Tillmann 
and  Henblein,  Z.  Nahr.  Genussm.,  24,  429;  C.  A.  7,  38. 


BOILER  SCALE 

General. — Break  up  pieces  as  representative  as  possible  of 
the  scale  and  grind  in  an  iron  or  porcelain  mortar.  Then  quarter 
down  and  pulverize  a  small  sample  finely  in  an  agate  mortar  for 
analysis. 

Moisture. — Dry  5  grams  of  the  powder  at  105°  C.  to  constant 
weight.     Report  the  loss  in  weight  as  moisture. 

Oil. — Transfer  the  dry  powder  left  from  the  moisture  deter- 
mination to  an  extraction  thimble  and  extract  with  ether  in  a 
Soxhlet  extractor  in  the  usual  way,  collecting  the  extract  in  a 
weighed  Soxhlet  flask.  Distill  off  the  ether  and  dry  the  flask  at 
100°  C.  to  constant  weight. 

Organic  and  Volatile  Matter. — Weigh  out  1  gram  of  the  pow- 
dered material  in  a  platinum  crucible  and  gently  ignite  until  the 
organic  matter  is  burned  off.  Cool  the  crucible  in  a  desiccator 
and  weigh.  From  this  weight  subtract  the  moisture  previously 


MISCELLANEOUS  ANALYSES  523 

determined  and  report  the  difference  as  Organic  and  Volatile 
Matter.  [See  note  (2).] 

Silicious  Matter. — Transfer  the  residue  from  the  above  deter- 
mination with  a  little  water  to  a  250  cc.  beaker.  Cover  the  beaker 
with  a  watch  glass  and  add  HC1  in  excess.  Dilute  to  abo'ut  150  cc., 
heat  to  boiling  and  filter.  Wash  thoroughly  with  hot  water. 
Ignite  the  residue  in  a  platinum  crucible,  first  over  a  burner  and 
then  in  a  blast  lamp.  Cool  in  a  desiccator  and  weigh. 

Iron  and  Aluminum  Oxides. — To  the  filtrate  from  the  silicious 
matter  add  a  few  drops  of  cone.  HNOs  and  heat  to  boiling.  Add 
10  cc.  of  NILiCl  solution  and  then  NH4OH  in  excess.  Boil  until 
there  is  only  a  faint  odor  of  NHs.  Filter  and  wash  thoroughly. 
Ignite,  blast,  and  weigh  as  Fe2O3+Al2Os. 

Lime. — To  the  filtrate  from  the  above  add  a  few  cc.  of  NEUOH, 
heat  to  boiling  and  add  (NH4)2C2O4  solution  in  excess.  Boil 
until  the  precipitate  becomes  granular.  Let  stand  in  a  warm  place 
until  the  solution  becomes  clear.  Filter  and  wash  with  hot  water. 
Ignite  the  precipitate  first  in  a  Tirrill  burner  and  then  in  a  blast 
lamp  to  constant  weight.  Cool  in  desiccator  and  weigh  rapidly 
as  CaO.  (If  preferred,  the  CaC2O4  may  be  titrated  with  0.1  N 
KMn04  as  on  page  518.) 

Magnesia. — Make  the  filtrate  from  the  CaO  determination 
slightly  acid  with  HC1  and  evaporate  until  crystallization  begins. 
Add  sufficient  water  to  just  redissolve  any  crystals  which  form. 
Cool  thoroughly.  Add  at  least  10  cc.  of  10%  sodium  phosphate 
or  ammonium  phosphate  solution.  Stir  briskly  with  a  stirring 
rod  and  rubber  policeman  until  precipitation  starts,  and  add  about 
one-quarter  the  volume  of  strong  NKiOH.  Let  stand  overnight, 
if  possible.  If  the  analysis  is  urgent,  place  the  beaker  in  ice 
water  and  stir  for  one-half  hour.  Filter  the  precipitate  on  a 
weighed  Gooch  crucible  and  wash  with  magnesia  wash  water  (see 
page  518).  Dry  the  precipitate  in  the  oven  and  ignite  strongly 
over  a  Tirrill  burner  to  constant  weight  and  weigh  as  Mg2?207. 
Calculate  to  MgO. 

CALCULATION.— Mg2P207X0.3621  =  MgO. 

Sulfur  Trioxide. — Boil  1  gram  of  the  finely  powdered  material 
with  cone.  HC1,  dilute  with  two  volumes  of  water  and  boil  again. 
Filter  and  wash  thoroughly  with  hot  water.  Heat  the  filtrate  to 
boiling  and  add  slowly  10  cc.  of  10%  BaCl2  solution.  Boil  gently 


524  TECHNICAL  METHODS  OF  ANALYSIS 

until  the  precipitate  settles  clear.  Filter,  wash  free  from  chlorides 
with  hot  water,  ignite  the  precipitate,  and  weigh  as  BaSO4. 
Calculate  to  SO3. 

CALCULATION.— BaS04  X  0.3430  =  SO3. 

Chlorine. — Weigh  out  5  grams  of  the  dry  powdered  scale.  Add 
100  cc.  of  water  and  heat  to  boiling.  Filter  and  wash  thoroughly, 
catching  the  filtrate  in  a  porcelain  dish.  Cool,  add  a  few  drops 
of  K2Cr04  indicator  and  titrate  with  standard  AgN03  solution 
to  the  appearance  of  a  reddish  color.  Since  the  amount  of  chlorides 
present  is  generally  small,  a  weak  AgN03  solution  (0.01  N)  should 
be  used  in  titrating.  If  the  scale  forms  an  alkaline  solution,  it 
must  be  exactly  neutralized  with  dil.  H2S04  and  phenolphthalein 
before  titrating. 

CALCULATION.— 1  cc.  of  0.01  N  AgN03  =  0.000355  gram  Cl. 

Final  Calculations. — Calculate  the  Cl  (if  any  is  present)  to 
NaCl.  Calculate  the  SO3  to  CaS04;  and  if  an  excess  of  S03 
remains,  calculate  it  to  MgS04.  In  case  the  SO3  is  insufficient  to 
combine  with  the  CaO,  calculate  the  remainder  of  the  CaO  to 
CaCO3.  Report  any  MgO  which  is  in  excess  of  the  S03  as  MgO 
and  not  as  MgC03,  since  the  latter  is  decomposed  at  the  tempera- 
ture of  the  boiler. 

NOTES. — (1)  Other  substances  such  as  copper,  zinc,  etc.,  from  local  sources 
are  occasionally  found  in  boiler  scales.  If  such  are  present,  they  may  be 
determined  by  the  usual  quantitative  methods. 

(2)  The  determination  of  organic  and  volatile  matter  is  usually  too  high, 
owing  to  the  partial  loss  of  CO2  from  carbonates,  so  it  is  generally  advisable  to 
take  the  organic  and  volatile  "  by  difference  " — merely  using  the  actual  deter- 
mination as  a  rough  check  upon  it.  Any  oil  present  is,  of  course,  included 
in  the  organic  and  volatile  matter. 

FERTILIZERS 

Mechanical  Analysis  of  Bone  and  Tankage. — Transfer  100 
grams  of  the  original  material  to  a  sieve  having  circular  openings 
0.02  inch  (0.5  mm.)  in  diameter  and  sift,  breaking  the  lumps  by 
means  of  a  soft  rubber  pestle  if  the  material  has  a  tendency  to 
cake.  Weigh  the  coarse  material  remaining  on  the  sieve  and 
determine  the  fine  portion  by  difference. 

Preparation  of  Sample. — Reduce  the  gross  sample  by  quarter- 
ing to  an  amount  sufficient  for  analysis.  Transfer  to  a  sieve  having 
circular  openings  0.04  inch  (1  mm.)  in  diameter  and  sift,  breaking 


MISCELLANEOUS  ANALYSES  525 

the  lumps  with  a  soft  rubber  pestle.  Grind  in  a  mortar  the  part 
remaining  in  the  sieve  until  all  the  particles  will  pass  through. 
Mix  thoroughly  and  preserve  in  tightly  stoppered  bottles.  Grind 
and  sieve  as  rapidly  as  possible  to  avoid  loss  or  gain  of  moisture. 

Moisture. — Heat  2  grams,  prepared  as  above,  for  five  hours  in  a 
water  oven  at  the  temperature  of  boiling  water.  With  potash 
salts,  NaN03,  and  (NEU)2SO4  heat  1-5  grams  at  about  130°  C. 
to  constant  weight.  The  loss  in  weight  is  considered  as  moisture. 

Nitrogen. — Test  for  nitrates  as  follows:  Mix  5  grams  of  the 
fertilizer  with  25  cc.  of  hot  water  and  filter.  Cool  and  add  to  a 
portion  of  the  solution  2  volumes  of  cone.  H2S04,  free  from  HNOs 
and  nitrous  oxides.  Let  the  mixture  cool  and  add  cautiously  a 
few  drops  of  a  cone,  solution  of  FeSO4  down  the  side  of  the  tube 
so  that  the  fluids  do  not  mix.  If  nitrates  are  present,  the  junction 
shows  at  first  a  purple,  then  a  brown  color;  or  if  only  a  very  minute 
quantity  is  present,  a  reddish  color.  To  another  portion  of  the 
solution  add  1  cc.  of  a  1%  solution  of  NaNOs  and  test  as  before  to 
determine  whether  sufficient  H2S04  was  added  in  the  first  test. 

If  nitrates  are  present,  determine  the  various  forms  of  nitrogen 
as  described  on  page  64.  If  nitrates  are  absent,  determine  merely 
organic  and  ammoniacal  nitrogen 

Phosphoric  Acid  (Gravimetric  Method). — PREPARATION  OF 
REAGENTS. — (a)  Ammonium  citrate  solution. — Dissolve  370  grams 
of  commercial  critic  acid  in  1500  cc.  of  water;  nearly  neutralize 
with  commercial  NHiOH;  cool,  add  NILiOH  until  exactly  neutral 
(testing  with  litmus  or  azolitmin  paper),  and  dilute  sufficiently 
to  make  the  sp.  gr.  1.09  at  20°  C.  The  volume  "will  be  about  2 
liters. 

(b)  Molybdate  solution. — Dissolve  100  grams  of  molybdic  acid  in 
144  cc.  of  cone.  NHiOH,  and  271  cc.  of  water;   slowly  and  with 
constant  stirring,  pour  the  solution  thus  obtained  into  489  cc. 
of  cone.  HNOs  and  1148  cc.  of  water.     Keep  the  mixture  in  a  warm 
place  for  several  days,  or  until  a  portion  heated  to  40°  C.  deposits 
no  yellow  precipitate  of  ammonium  phosphomolybdate.     Decant 
the  solution  from  any  sediment  and  preserve  in  glass-stoppered 
bottles. 

(c)  Ammonium    nitrate    solution. — Dissolve    200    grams    of 
commercial   NHiNOs,  free  from   phosphate,  in  water  and  dilute 
to  2  liters. 


526  TECHNICAL  METHODS  OF  ANALYSIS 

(d)  Magnesia  mixture. — Dissolve  22  grams  of  recently  ignited 
calcined  MgO  iirdil.  HC1,  avoiding  an  excess  of  acid.     Add  a  little 
calcined  MgO  in  excess,  and  boil  a  few  minutes  to  precipitate  Fe, 
Al  and  P2O5;   filter;    add  280  grams  of  NILtCl,  261  cc.  of  cone. 
NELiOH,  and  dilute  to  2  liters.     Instead  of  the  solution  of  22  grams 
of  calcined  MgO  in  HC1,  110  grams  of  crystallized  MgCl2-6H2O 
may  be  used. 

(e)  Dilute   NH±OH  for   washing. — Dilute    100    cc.    of   cone. 
NILtOH  to  1  liter. 

(/)  Magnesium  nitrate  solution. — Dissolve  320  grams  of  cal- 
calcined  MgO  in  HNOs,  avoiding  an  excess  of  acid;  then  add  a 
little  calcined  MgO  in  excess;  boil,  filter  from  the  excess  of 
MgO,  Fe(OH)s,  etc.,  and  dilute  with  water  to  2  liters. 

TOTAL  PHOSPHORIC  ACID. — (a)  Methods  of  making  solution. — 
Treat  2.5  grams  of  the  sample  by  one  of  the  methods  given  below. 
After  solution,  cool,  dilute  to  250  cc.,  mix,  and  pour  on  a  dry 
filter. 

(I)  Ignite  and  dissolve  in  HCL 

(II)  Evaporate  with  5  cc.  of  Mg(NOs)2  solution,  ignite  and 
dissolve  in  HC1. 

(III)  Boil  with  20-30  cc.  of  cone.  H2SO4  in  a  Kjeldahl  flask, 
adding  2-4  grams  of  NaNOa  or  KNOs  at  the  beginning  of  the 
digestion  and  a  small  quantity  after  the  solution  has  become  nearly 
colorless,  or  adding  the  nitrate  in  small  portions  from  time  to  time. 
After  the  solution  is  colorless  add  150  cc.  of  water  and  boil  for  a 
few  minutes. 

(IV)  Digest  in  a  Kjeldahl  flask  with  strong  H2S04  and  such 
other  reagents  as  are  used  in  either  the  plain  or  modified  Kjeldahl 
or  Gunning  method  for  estimating  nitrogen.     (See    page    64.) 
Do  not  add  any  KMnO4,  but  after  the  solution  has  become  color- 
less add  about  100  cc.  of  water  and  boil  for  a  few  minutes. 

(V)  Dissolve  in  30  cc.  of  cone.  HNOs  and  a  small  quantity 
of  HC1  and  boil  until  organic  matter  is  destroyed. 

(VI)  Add  30  cc.   of  cone.   HC1,  heat,   and  add  cautiously, 
in  small  quantities  at  a  time,  about  0.5  gram  of  finely  pulverized 
KClOa  to  destroy  organic  matter. 

(VII)  Dissolve  in  15-30  cc.  of  cone.  HC1  and  3-10  cc.  of  HNO3. 
This   method   is   recommended   for   fertilizers   containing  much 
iron  or  aluminum  phosphate. 


MISCELLANEOUS  ANALYSES  527 

(b)  Determination. — Take  an  aliquot  of  the  solution  prepared 
above  corresponding  to  0.25  gram,  0.50  gram,  or  1  gram;  neutralize 
with  NH4OH  and  clear  with  a  few  drops  of  HNOs.  In  case  HC1 
or  H2SO4  has  been  used  as  a  solvent,  add  about  15  grams  of  dry 
NH4NOs  or  a  solution  containing  that  amount.  To  the  hot 
solution  add  60-80  cc.  of  molybdate  solution  for  every  0.1  gram 
of  P2Os  that  is  present.  Digest  at  about  65°  C.  for  one  hour  and 
test  the  clear  supernatant  liquor  for  complete  precipitation  by  the 
addition  of  more  molybdate  solution.  Filter  and  wash  with  cold 
water  or,  preferably,  with  NEUNOs  solution.  Dissolve  the  pre- 
cipitate on  the  filter  with  NH^OH  and  hot  water  and  wash  into  a 
beaker  to  a  bulk  of  not  more  than  100  cc.  Nearly  neutralize  with 
HC1,  cool,  and  add  magnesia  mixture  from  a  burette,  slowly 
(about  1  drop  per  second),  stirring  vigorously.  After  fifteen 
minutes  add  12  cc.  of  cone.  NKUOH.  Let  stand  till  clear  (two 
hours  is  usually  enough),  filter  on  a  weighed  Gooch  crucible,  wash 
with  the  weak  NHs  solution  until  practically  free  from  chlorides; 
ignite  to  whiteness  or  to  a  grayish  white  and  weigh  as  Mg2P20r. 
Calculate  to  P2Os. 

CALCULATION.— Mg2P2O7  X  0.6379  =  P2O5. 

WATER-SOLUBLE  PHOSPHORIC  ACID. — Place  2  grams  of  the 
sample  on  a  9  cm.  filter,  wash  with  successive  small  portions  of 
water,  allowing  each  portion  to  pass  through  before  adding  more, 
until  the  nitrate  measures  about  250  cc.  If  the  nitrate  be  turbid, 
add  a  little  HNOs.  Make  up  to  any  convenient  definite  volume, 
mix  well,  use  an  aliquot  *  and  proceed  as  under  Total  Phosphoric 
Acid,  above. 

CITRATE-INSOLUBLE  PHOSPHORIC  ACID. — (a)  Determination  in 
Acidulated  Samples. — Heat  100  cc.  of  strictly  neutral  ammonium 
citrate  solution  (sp.  gr.  1.09)  to  65°  C.  in  a  flask  placed  in  a  warm 
water  bath,  keeping  the  flask  loosely  stoppered  to  prevent  evapo- 
ration. The  level  of  the  water  in  the  bath  should  be  above  that 
of  the  liquid  in  the  flask.  When  the  citrate  solution  in  the  flask 
has  reached  65°  C.,  drop  into  it  the  filter  containing  the  washed 
residue  from  the  water-soluble  P20s  determination,  close  tightly 
with  a  smooth  rubber  stopper  and  shake  violently  until  the  filter 
paper  is  reduced  to  a  pulp  relieving  the  pressure  by  momentarily 

*  An  aliquot  corresponding  to  0.5  gram  of  the  original  sample  is  generally  a 
suitable  amount. 


528  TECHNICAL  METHODS  OF  ANALYSIS 

removing  the  stopper.  Place  the  flask  in  the  bath  and  maintain 
it  at  such  a  temperature  that  the  contents  of  the  flask  will  stand 
at  exactly  65°  C.  Shake  the  flask  every  five  minutes.  At  the 
expiration  of  exactly  thirty  minutes  from  the  time  the  filter  and 
residue  are  introduced,  remove  the  flask  from  the  bath  and  imme- 
diately filter  the  contents  as  quickly  as  possible  through  a  rapid 
filter  paper.  Wash  with  water  at  65°  C.  until  the  volume  of 
filtrate  is  about  350  cc.,  allowing  time  for  thorough  draining  before 
adding  new  portions  of  water.  Return  the  filter  with  contents  to 
the  digestion  flask,  add  30-35  cc.  of  cone.  HNOs,  5-10  cc.  of 
cone.  HC1  and  boil  until  all  phosphate  is  dissolved.  Dilute  the 
solution  to  200  cc.,  mix  well,  filter  through  a  dry  filter;  take  a 
definite  portion  of  the  filtrate  and  proceed  as  under  Total  Phos- 
phoric Acid,  above. 

(b)  Determination  in  Non-acidulated  Samples — In  case  a 
determination  of  citrate-insoluble  P2Os  is  required  in  non-acid- 
ulated samples,  treat  2  grams  of  the  phosphatic  material  without 
previous  washing  with  water,  precisely  in  the  way  above  described, 
except  that;  in  case  the  substance  contains  much  animal  matter 
(bone,  fish,  etc.),  the  residue  insoluble  in  ammonium  citrate  is  to 
be  dissolved  by  any  one  of  the  processes  (II),  (III),  or  (IV) 
described  under  Total  Phosphoric  Acid. 

CITRATE-SOLUBLE  PHOSPHORIC  ACID. — The  sum  of  the  water- 
soluble  and  citrate-insoluble,  subtracted  from  the  total,  gives  the 
citrate-soluble  phosphoric  acid  (P2Os). 

Phosphoric  Acid  (Optional  Volumetric  Method). — PREPARA- 
TION OF  REAGENTS. — (a)  Molybdate  solution. — To  100  cc.  of 
molybdate  solution,  prepared  as  directed  above  under  Gravimetric 
Method,  add  5  cc.  of  cone.  HNOs-  This  solution  should  be 
filtered  each  time  before  using. 

(b)  Standard  NaOH  or   KOH  solution.— Dilute  323.8  cc.  of 
normal  alkali,  free  from  carbonates,  to  1  liter.     100  cc.  of  the 
solution  should  neutralize  32.38  cc.   of  normal  acid.     1   cc.   is 
equal  to  0.001  gram  of  P2O5  (1%  of  P2Os  on  a  basis  of  0.1  gram 
of  substance). 

(c)  Standard  acid  solution. — The  strength  of  this  solution  is 
the  same  as,  or  one-half  of,  the  standard  alkali  solution,  and  is 
determined  by  titrating  against  that  solution,  using  phenolphthal- 
ein  indicator.     Either  HC1  or  HNOs  may  be  used. 


MISCELLANEOUS  ANALYSES  529 

(d)  Phenolphthalein  solution. — Dissolve  1  gram  of  phenolphtha- 
lein  in  100  cc.  of  alcohol. 

TOTAL  PHOSPHORIC  ACID. — (a)  Methods  of  Making  Solution. 
— Dissolve  according  to  methods  (II),  (V),  (VI),  or  (VII),  as 
described  above  under  Gravimetric  Method  [preferably  by  (V), 
when  these  acids  are  a  suitable  solvent]  and  dilute  to  200  cc.  with 
water. 

(6)  Determination. — (I)  For  percentages  of  5  or  below  use 
.an  aliquot  corresponding  to  0.4  gram  of  substance;  for  percentages 
between  5  and  20  use  an  aliquot  corresponding  to  0.2  gram;  and 
for  percentages  above  20  use  an  aliquot  corresponding  to  0.1 
gram.  Add  5-10  cc.  of  HNOs,  depending  on  the  method  of  solu- 
tion (or  the  equivalent  in  NEUNOs);  nearly  neutralize  with 
NH4OH;  "dilute  to  75-100  cc.,  heat  in  a  water  bath  to  60-65°  C., 
and  for  percentages  below  5  add  20-25  cc.  of  freshly  filtered  molyb- 
date  solution;  whereas  for  percentages  between  5  and  20  add 
30-35  cc.  of  molybdate  solution.  For  higher  percentages  add 
sufficient  to  insure  complete  precipitation.  Stir,  let  stand  about 
fifteen  minutes,  filter  at  once  and  wash  once  or  twice  with  water 
by  decantation,  using  25-30  cc.  each  time,  agitating  the  precipitate 
thoroughly  and  allowing  to  settle.  Transfer  to  the  filter  and  wash 
with  cold  water  until  two  fillings  of  the  filter  yield  a  pink  color 
upon  the  addition  of  phenolphthalein  and  1  drop  of  the  standard 
alkali.  Transfer  the  precipitate  and  filter  to  a  beaker  or  flask, 
dissolve  in  a  small  excess  of  the  standard  alkali,  add  a  few  drops  of 
phenolphthalein  solution,  and  titrate  with  standard  acid. 

(II)  Proceed  as  directed  in  (I),  with  this  exception:  Heat  in  a 
water  bath  at  45-50°  C.,  add  the   molybdate   solution,  and  let 
remain  in  the  bath  with  occasional  stirring  for  thirty  minutes. 

(III)  Proceed  as  in  (I)  to  the  point  where  the  solution  is 
ready  to  place  in  the  water  bath.     Then  cool  the  solution  to  room 
temperature,  add  molybdate  solution  at  the  rate  of  75  cc.  for  each 
0. 1  gram  of  P2Os  present,  place  the  stoppered  flask  containing  the 
solution  in  a  shaking  apparatus  and  shake  for  thirty  minutes  at 
room  temperature.     Filter  at  once,  wash,  and  titrate  as  in  the 
preceding  method. 

WATER-SOLUBLE  PHOSPHORIC   ACID. — Dissolve  according  to 
directions  given  under  the  Gravimetric  Method  for  Water-soluble 
To  an  aliquot  portion  of  the  solution  corresponding  to  0,2 


530  TECHNICAL  METHODS  OF  ANALYSIS 

or  0.4  gram,  add  10  cc.  of  cone.  HNOs  and  then  NH4OH  until  a 
slight  permanent  precipitate  is  formed.  Dilute  to  60  cc.  and 
proceed  as  under  Determination  (I)  for  Total  P20s,  on  page  529. 

CITRATE-INSOLUBLE  PHOSPHORIC  ACID. — Make  the  solution 
according  to  the  directions  given  under  the  Gravimetric  Method 
(IV)  and  determine  the  ?2O5  in  an  aliquot  corresponding  to  0.4 
gram  as  directed  under  Total  P205,  Determination  (I). 

CITRATE-SOLUBLE  PHOSPHORIC  ACID. — The  sum  of  the  water- 
soluble  and  citrate-insoluble,  subtracted  from  the  total,  gives 
the  citrate-soluble  P2O5. 

Potash. — The  K^O  is  determined  as  on  page  41. 

NOTE. — This  is  the  procedure  of  the  Association  of  Official  Agricultural 
Chemists  as  given  in  its  Journal,  Methods  of  Analysis  (1916),  page  1.  The 
methods  are  official,  excepting  the  mechanical  analysis  of  bone  and  tankage, 
which  is  tentative. 

CARBOLINEUM  AND  SIMILAR  WOOD-PRESERVING  OILS 

General. — About  one  quart  of  oil  is  required  for  a  complete 
analysis.  It  is  possible  to  make  a  single  analysis  on  about  a 
pint,  but  the  above  amount  provides  for  a  check  determination 
in  case  anything  happens  to  the  first.  Before  analyzing,  thor- 
oughly liquefy  the  sample  and  mix  it  well  by  shaking  and  stirring. 

Specific  Gravity  at  38°  C. — Fill  the  hydrometer  cylinder  with 
the  liquefied  oil  and  place  the  cylinder  in  water,  then  heat  until 
the  temperature  of  the  oil  is  several  degrees  higher  than  38°  C. 
Let  the  water  cool  until  the  oil  has  reached  a  temperature  of  38° 
C.  Thoroughly  stir  the  oil,  place  the  hydrometer  in  the  cylinder, 
and  carefully  observe  the  reading.  Take  care  that  the  hydrometer 
does  not  touch  the  bottom  or  sides  of  the  cylinder  when  the 
reading  is  made. 

Condition  at  38°  C. — Heat  about  100  cc.  of  the  oil  in  a  beaker 
to  a  temperature  of  not  less  than  45°  C.  and  let  the  oil  cool  grad- 
ually. When  a  temperature  of  38°  C.  is  reached,  examine  the 
oil  carefully  by  means  of  a  glass  stirring  rod.  No  solid  crystalline 
particles  should  appear  on  the  rod  when  withdrawn  from  the  oil. 
A  cloudiness  of  the  oil  may  be  disregarded. 

Flash  Point. — Place  an  evaporating  dish,  about  4  or  4.5 
inches  in  diameter,  on  an  asbestos  diaphragm  of  sufficient  size  to 


MISCELLANEOUS  ANALYSES  531 

extend  several  inches  beyond  the  dish.  Cut  a  hole  in  the  center 
of  the  diaphragm  about  half  the  maximum  diameter  of  the  dish 
and  set  the  dish  in  it.  Cover  the  bottom  of  the  dish  with  dry 
sand  to  a  depth  of  about  0.25  inch  and  place  an  evaporating  dish, 
about  3  inches  in  diameter,  on  the  sand.  Fill  the  remaining  space 
between  the  two  dishes  with  sand  until  it  reaches  nearly  to  the 
rim  of  the  inner  dish.  Arrange  a  thermometer  so  that  the  bulb 
is  inside  and  about  0.25  inch  above  the  bottom  of  the  inner  dish. 
Pour  some  of  the  liquefied  oil  into  the  dish  until  it  is  about  three- 
quarters  full.  Place  a  low  flame  beneath  the  sand  bath,  with  a 
suitable  guard  to  protect  it  from  draughts,  which  should  be  care- 
fully excluded  from  the  vicinity  of  the  testing  apparatus.  Heat 
so  that  the  temperature  of  the  oil  will  increase  about  3°  C.  per 
minute.  Apply  a  small  flame  just  above  the  surface  of  the  oil 
for  every  two  degrees'  rise  of  temperature  until  the  flame  flashes 
across  th  3  surface  of  the  oil.  The  temperature  of  the  oil  when  this 
occurs  is  the  flash  point.  Report  results  in  Centigrade  degrees. 

Burning  Point. — Continue  the  heating  and  the  application  of 
the  testing  flame  until  the  oil  ignites  and  burns  for  five  seconds 
or  more.  The  temperature  at  which  this  occurs  is  the  burning 
point. 

Water. — Weigh  out  10  grams  of  the  original  oil  into  a  300  cc. 
Erlenmeyer  flask.  Add  to  this  75  cc.  of  Xylol  which  has  pre- 
viously been  saturated  with  water  and  proceed  as  directed  on 
page  271. 

Fractionation. — Arrange  the  apparatus  for  distillation  as  shown 
in  Fig.  26.. 

For  the  distillation  use  a  200  cc.  Jena  *  glass  round-bottomed 
fractionating  flask  which  shall  satisfy  the  following  requirements: 

It  shall  hold  not  less  than  190  cc.  nor  more  than  210  cc.  when 
filled  to  the  base  line  of  the  neck.  The  bulb  shall  be  2|  inches  in 
diameter.  The  neck  shall  be  yf  inch  in  diameter  and  4  inches  in 
length.  The  side  arm  shall  be  taken  off  at  a  point  equidistant 
from  the  top  and  base  of  the  neck. 

Connect  an  air  condenser  14  inches  long  and  0.5  inch  in  diam- 
eter to  the  side  arm  of  the  flask,  as  shown  in  the  figure,  in  order 
to  insure  complete  condensation  of  the  distillate. 

*  Or  Pyrex. 


532 


TECHNICAL  METHODS  OF  ANALYSIS 


Before  setting  up  the  apparatus,  weigh  the  flask  accurately 
and  then  pour  into  it,  by  means  of  a  stirring  rod,  exactly  100  grams 
of  the  thoroughly  liquefied  and  mixed  oil. 

Before  beginning  the  distillation,  fit  the  thermometer  through 
the  stopper  in  the  neck  of  the  flask  so  that  the  top  of  the  bulb 
comes  just  below  the  lower  edge  of  the  side  arm  tube.  Do  not 
move  the  thermometer  during  the  distillation.  Rest  the  flask 
in  a  hole  1.75  inches  in  diameter  in  an  asbestos  board  supported 
on  the  ring  stand.  To  protect  the  flask  from  draughts,  provide 
an  asbestos  shield  surrounding  the  flask,  resting  on  the  asbestos 


Iron  Support 


Ajr  Con 


Ease  of  Stand 


FIG.  26. — Distillation  Apparatus  for  Carbolineum. 


board,  and  rising  to  the  level  of  the  top  of  the  bulb.  Play  an 
open  flame  on  the  bottom  of  the  flask  and  apply  the  heat  so  reg- 
ulated that  the  distillate  passes  over  at  the  rate  of  about  1  drop 
per  second. 

It  is  to  be  understood  that  the  distillation  has  commenced  as 
soon  as  the  first  drop  of  the  distillate  appears  in  the  delivery  tube 
of  the  flask  and  ended  when  a  temperature  of  360°  C.  is  reached. 

NOTE. — The  distillation  of  some  samples  of  oil  may  be  accompanied,  espe- 
cially during  the  first  few  moments,  by  a  violent  spattering  of  the  liquid  and 
small  quantities  may  go  over  into  the  test-tubes.  This  can  usually  be  avoided 
by  inserting  a  small  piece  of  unglazed  porcelain  in  the  flask  before  commencing 
the  distillation. 

Distillate. — Weigh  up  accurately  7  test  tubes  properly  labeled 
for  identification.  Collect  the  fractions  of  the  distillate  in  these 


MISCELLANEOUS  ANALYSES 


533 


test-tubes  according  to  the  temperatures  given  in  the  following 
table: 


Test-tube 
No. 

Temperature 
°C. 

Fraction 

1 

Up  to  205 

Water,  tar  acids,   naphtha- 

lene (if  present) 

2 
3 

205-235  \ 
235-270  J 

Tar  acids,  naphthalene 

4 

270-300 

5 
6 

300-315 
315-330 

Anthracene,  anthracene  oil 

7 

330-360 

Residue  above  360 

Residue  in  flask 

After  completion  of  the  distillation,  drive  over  all  the  material 
which  is  in  the  air  condenser  by  playing  a  flame  over  the  condenser. 
Weigh  up  each  of  the  test-tubes  and  also  weigh  the  flask  with  the 
residue  after  it  is  cool. 

Calculate  the  percentages  of  the  different  fractions  and  add 
them  together.  The  sum  should  be  within  0.5%  of  100%,  except 
when  there  is  a  considerable  amount  of  water  present.  If 
the  loss,  after  carefully  checking  the  figures,  is  found  to  be  large 
when  a  sample  containing  little  water  or  other  low-boiling 
constituents  is  distilled,  repeat  the  distillation. 

Sulfonation  Residue. — Carry  out  this  test  on  the  fractions  of 
the  carbolineum  distilling  between  300  and  330°  C.  (For  Dead 
Oil  of  Coal  Tar  the  test  should  be  carried  out  on  the  fractions  dis- 
tilling between  300  and  360°  C.)  Transfer  the  fractions  to  a 
large-mouthed  round  flask  of  about  250  cc.  capacity.  Then  add 
4-5  volumes  of  cone.  H2SO4  for  each  volume  of  distillate  under 
test.  Heat  for  about  five  minutes  with  frequent  shaking;  then 
let  stand  about  one-half  hour,  shaking  at  intervals.  Slowly  pour 
the  mixture  of  acid  and  oil  into  a  liter  beaker  containing  enough 
water  to  dissolve  the  sulfonic  acids  formed.  When  cool,  transfer 
from  the  beaker  to  a  separatory  funnel  and  let  settle  for  one  hour, 
or  longer  if  necessary,  until  the  undissolved  oil  separates  clearly. 
Draw  off  and  reject  the  water  containing  the  sulfonic  acids. 


532 


TECHNICAL  METHODS  OF  ANALYSIS 


Before  setting  up  the  apparatus,  weigh  the  flask  accurately 
and  then  pour  into  it,  by  means  of  a  stirring  rod,  exactly  100  grams 
of  the  thoroughly  liquefied  and  mixed  oil. 

Before  beginning  the  distillation,  fit  the  thermometer  through 
the  stopper  in  the  neck  of  the  flask  so  that  the  top  of  the  bulb 
comes  just  below  the  lower  edge  of  the  side  arm  tube.  Do  not 
move  the  thermometer  during  the  distillation.  Rest  the  flask 
in  a  hole  1.75  inches  in  diameter  in  an  asbestos  board  supported 
on  the  ring  stand.  To  protect  the  flask  from  draughts,  provide 
an  asbestos  shield  surrounding  the  flask,  resting  on  the  asbestos 


Iron  Support 


•o 


Thermometer-^tt 
Cork  Stopper 


Air  Condenser 


Flask 


Ease  of  Stand 


FIG.  26. — Distillation  Apparatus  for  Carbolineum. 

board,  and  rising  to  the  level  of  the  top  of  the  bulb.  Play  an 
open  flame  on  the  bottom  of  the  flask  and  apply  the  heat  so  reg- 
ulated that  the  distillate  passes  over  at  the  rate  of  about  1  drop 
per  second. 

It  is  to  be  understood  that  the  distillation  has  commenced  as 
soon  as  the  first  drop  of  the  distillate  appears  in  the  delivery  tube 
of  the  flask  and  ended  when  a  temperature  of  360°  C.  is  reached. 

NOTE. — The  distillation  of  some  samples  of  oil  may  be  accompanied,  espe- 
cially during  the  first  few  moments,  by  a  violent  spattering  of  the  liquid  and 
small  quantities  may  go  over  into  the  test-tubes.  This  can  usually  be  avoided 
by  inserting  a  small  piece  of  unglazed  porcelain  in  the  flask  before  commencing 
the  distillation. 

Distillate. — Weigh  up  accurately  7  test  tubes  properly  labeled 
for  identification.  Collect  the  fractions  of  the  distillate  in  these 


MISCELLANEOUS  ANALYSES 


533 


test-tubes  according  to  the  temperatures  given  in  the  following 
table: 


Test-tube 

No. 

Temperature 
°C. 

Fraction 

1 

Up  to  205 

Water,  tar  acids,   naphtha- 

lene (if  present) 

2 
3 

205-235  \ 
235-270  / 

Tar  acids,  naphthalene 

4 

270-300 

5 
6 

300-315 
315-330 

Anthracene,  anthracene  oil 

7 

330-360 

Residue  above  360 

Residue  in  flask 

After  completion  of  the  distillation,  drive  over  all  the  material 
which  is  in  the  air  condenser  by  playing  a  flame  over  the  condenser. 
Weigh  up  each  of  the  test-tubes  and  also  weigh  the  flask  with  the 
residue  after  it  is  cool. 

Calculate  the  percentages  of  the  different  fractions  and  add 
them  together.  The  sum  should  be  within  0.5%  of  100%,  except 
when  there  is  a  considerable  amount  of  water  present.  If 
the  loss,  after  carefully  checking  the  figures,  is  found  to  be  large 
when  a  sample  containing  little  water  or  other  low-boiling 
constituents  is  distilled,  repeat  the  distillation. 

Sulfonation  Residue. — Carry  out  this  test  on  the  fractions  of 
the  carbolineum  distilling  between  300  and  330°  C.  (For  Dead 
Oil  of  Coal  Tar  the  test  should  be  carried  out  on  the  fractions  dis- 
tilling between  300  and  360°  C.)  Transfer  the  fractions  to  a 
large-mouthed  round  flask  of  about  250  cc.  capacity.  Then  add 
4-5  volumes  of  cone.  H^SCU  for  each  volume  of  distillate  under 
test.  Heat  for  about  five  minutes  with  frequent  shaking;  then 
let  stand  about  one-half  hour,  shaking  at  intervals.  Slowly  pour 
the  mixture  of  acid  and  oil  into  a  liter  beaker  containing  enough 
water  to  dissolve  the  sulfonic  acids  formed.  When  cool,  transfer 
from  the  beaker  to  a  separatory  funnel  and  let  settle  for  one  hour, 
or  longer  if  necessary,  until  the  undissolved  oil  separates  clearly. 
Draw  off  and  reject  the  water  containing  the  sulfonic  acids. 


534  TECHNICAL  METHODS  OF  ANALYSIS 

Transfer  all  the  oily  residue  to  a  tube  graduated  to  0.1  cc.  and 
measure  its  volume.     (See  note.) 

If  there  should  be  a  heavy  insoluble  residue,  it  is  probable 
that  the  sulfonation  has  been  incomplete.  In  this  case,  add  com- 
mon salt  to  the  water  until  the  residue  rises  to  the  top  of  the 
water  solution.  Separate  the  unsulfonated  oil  and  submit  it 
again  to  the  sulfonating  treatment.  In  case  the  residue  exceeds 
the  maximum  allowed  by  the  specifications,  treat  it  with  a  10% 
NaOH  solution.  If  the  residue  is  soluble  in  this  reagent,  the  sul- 
fonation test  may  be  regarded  as  giving  negative  results.  Separate 
and  measure  the  residue  of  oil  remaining  after  the  treatment  with 
NaOH  solution.  The  amount  of  residue  thus  found  is  reported 
as  "  sulfonation  residue."  It  is  a  measure  of  any  mineral  oil 
present. 

NOTE. — As  the  sulfonation  residue  is  generally  very  small,  we  have  found 
it  convenient  to  draw  off  all  but  about  10  cc.  of  the  lower  acid  layer  from  the 
separatory  funnel  and  then  drain  the  liquid  remaining  in  the  funnel  into  a 
"  color  carbon  tube  "  graduated  0-25  cc.  in  0.1  cc.  Rinse  the  funnel  out  with 
ether  and  drain  this  into  the  tube.  Then  immerse  the  tube  in  warm  water  to  a 
level  slightly  above  the  level  in  the  tube.  Blow  a  gentle  current  of  air  into  the 
tube,  by  means  of  a  smaller  glass  tube  reaching  nearly  to  the  surface  of  the 
inner  liquid.  Slowly  raise  the  temperature  of  the  outside  water  by  pouring 
in  hot  water  (keep  flames  away)  until  the  ether  boils.  When  all  ether  has  been 
evaporated  off,  cool  to  room  temperature  and  read  the  volume  of  the  upper 
layer. 

Tar  Acids. — Carry  out  this  determination  on  the  fractions 
distilling  below  300°  C.  Transfer  them  to  a  beaker  of  about  300  cc. 
capacity  and  thoroughly  mix  by  stirring.  Add  30  cc.  of  NaOH 
solution  (17-18%)  to  the  oil  and  heat  the  whole  gently  for  two 
minutes,  with  frequent  stirring.  Transfer  the  mixture  to  a  large 
separatory  funnel  and  shake  vigorously  for  at  least  one  minute. 
Then  let  the  mixture  settle  and  draw  off  and  save  the  NaOH 
solution  which  forms  the  lower  liquid  layer. 

Repeat  this  operation  a  second  and  third  time,  using  20  cc. 
of  NaOH  solution  each  time.  Mix  the  3  NaOH  solutions  together, 
boil  vigorously  for  five  minutes  and  let  cool.  Transfer  to  a  special 
separatory  funnel  with  a  tube  graduated  to  0.1  cc.  Add  dilute 
H2SO4  (1:3)  until  the  solution  is  acid  to  litmus  paper.  About 
35  cc.  of  acid  will  be  required  and  care  must  be  taken  that  the 


MISCELLANEOUS  ANALYSES  535 

solution  be  kept  cool  while  adding  the  acid.  Let  stand  until  the 
tar  acids  are  well  separated  and  read  their  volume  (upper  layer). 
Compute  the  per  cent  by  dividing  this  volume  by  the  volume  of 
the  oil  taken  for  distillation;  viz.,  the  original  weight  of  oil  divided 
by  its  sp.  gr. 

Insoluble  in  Benzene. — Weigh  out  a  10-gram  portion  of  the 
original  oil  into  a  small  beaker  (about  100-150  cc.  capacity), 
add  20  cc.  of  benzene  (commercial  benzol)  and  filter  through  a 
weighed  alundum  (or  Gooch)  crucible  with  suction.  Wash  the 
residue  in  the  crucible  with  benzene  until  the  washings  run  color- 
less, thus  indicating  that  no  more  substances  will  dissolve;  dry 
the  crucible  at  110°  C.,  weigh  and  compute  the  per  cent  of  insoluble 
material. 

Ash. — Weigh  carefully  into  a  weighed  porcelain  crucible  about 
2  grams  of  the  oil,  and  heat  cautiously  over  a  low  flame  until 
the  oil  ignites.  When  the  flame  from  the  burning  oil  ceases, 
increase  the  heat,  and  after  all  organic  matter  has  apparently 
burned  off,  cool  and  weigh.  Reheat  and  reweigh,  until  a  constant 
weight  is  obtained. 

Acetic  Acid  and  Acetates  (Qualitative  Test). — Place  about  5  cc. 
of  the  oil  in  a  test-tube  and  add  about  one-half  of  its  volume  of 
alcohol.  Then  add  cone.  H2SO4  slowly,  drop  by  drop,  with  fre- 
quent shaking  until  the  liquid  is  hot  to  the  touch.  If  acetic  acid 
or  acetate  is  present,  the  characteristic  odor  of  ethyl  acetate  will 
develop. 

To  make  certain  of  this  odor  always  run  a  blank  at  the  same 
time,  adding  to  another  portion  of  5  cc.  of  the  original  oil  in  the 
test-tube  a  drop  of  acetic  acid,  and  then  carry  through  the  test  as 
above  described. 

NOTES. — (1)  The  apparatus  should  be  thoroughly  cleaned  after  each 
distillation.  To  remove  the  residue  from  the  retort,  add  some  of  the  oil  and 
heat  until  the  residue  is  all  dissolved.  Then  pour  out  the  oil  and  wash  the 
flask  with  hot  water  and  Sapolio. 

(2)  The  above  method,  with  the  exception  of  the  determination  of  water,  is 
ob tamed  from  Specification  1^-3432  of  the  Western  Electric  Company:  "Analy- 
sis of  Carbolineum  and  Similar  Wood  Preserving  Oils,"  November  10,  1911. 


536  TECHNICAL  METHODS  OF  ANALYSIS 


GYSPY  MOTH  CREOSOTE 

Specific  Gravity. — Determine  sp.  gr.  at  15.5°  C.  with  a  West- 
phal  balance. 

Fractional  Distillation. — Distill  200  cc.  of  the  creosote  in  a 
250  cc.  side-neck  distilling  flask  having  a  thermometer  inserted 
through  the  cork  stopper  in  the  neck  with  the  bulb  opposite  the 
side  tube  of  the  flask.  Conduct  the  distillation  at  the  rate  of 
approximately  2  drops  per  second,  collecting  each  fraction  in  a 
small  weighed  flask.  Take  the  following  fractions  and  report  the 
per  cent  by  weight: 

150-200°  C. 

200-245°  C. 

245-270°  C. 

270-320°  C. 

Residue  above  320°  C. 

Examine  the  residue  above  320°  C.  and  note  whether  heavy 
oils  have  been  added  to  the  creosote. 

Tar  Acids. — Employ  the  distillate  obtained  above,  by  dis- 
tilling up  to  a  temperature  of  320°  C.,  and  determine  the  tar  acids 
as  described  on  page  534.  Report  the  per  cent  of  tar  acids  by 
volume. 


COAL-TAR  ROOFING  PITCH 

General. — The  methods  for  testing  materials  like  coal-tar 
pitch  must  necessarily  be  more  or  less  empirical.  The  following 
procedures  are  from  specifications  prepared  for  the  Supervising 
Architect  of  the  U.  S.  Treasury  Department  and  are  valuable  in 
comparing  different  samples  where  straight  run  coal-tar  pitch  is 
desired. 

Melting  Point.— Determine  the  melting  point  by  the  Cube 
Method  as  described  on  page  542. 

Insoluble  in  Benzene. — Digest  10  grams  of  the  pitch  in  c.  P. 
toluene  on  the  steam  bath,  and  decant  through  a  filter  cup  con- 
sisting of  two  No.  575  C.  S.  &  S.  hardened  filter  papers  (previously 
dried  and  weighed).  Transfer  the  residue  to  this  filter,  and 
extract  with  c.  P.  benzene  in  any  form  of  extraction  apparatus 


MISCELLANEOUS  ANALYSES  537 

which  insures  hot  extraction,  until  the  washings  run  through 
practically  colorless.  Dry  and  weigh  the  papers  plus  the  residue. 
Specific  Gravity  at  60°  F.  —  Make  a  small  ball  of  the  material 
weighing  several  grams.  Make  sure  that  no  air  bubbles  are  oc- 
cluded within  it.  Weigh  this  carefully  on  a  tared  watch  glass  (A). 
Attach  a  silk  thread  to  it  and  again  weigh  (B).  Then  weigh  the 
ball  of  material  immersed  in  water,  which  is  at  60°  F.,  by  sus- 
pending the  thread  from  the  stirrup  of  the  balance  arm  (C). 
Subtract  (C)  from  (B).  This  gives  the  loss  in  weight  due  to  the 
buoyancy  of  water,  i.e.,  the  weight  of  an  equal  volume  of  water. 


Loss  on  Evaporation.  —  Determine  the  loss  in  weight  of  100 
grams  of  pitch  placed  in  a  flat  nickel  dish  2  inches  in  diameter,  and 
subjected  to  a  temperature  of  325°  F.,  for  seven  hours. 

Specific  Gravity  of  Distillate  to  670°  F.—  Distill  from  a  side- 
neck  flask  an  unweighed  quantity  of  the  sample  (50-100  grams). 
Have  the  bulb  of  the  thermometer  opposite  the  side-neck  of  the 
flask  and  continue  the  distillation  until  the  temperature  reaches 
670°  F.  Determine  the  sp.  gr.  of  the  distillate  with  a  pycnometer 
at  140°  F.,  compared  with  water  at  the  same  temperature. 

NOTES.  —  (1)  This  method  is  obtained  from  Bulletin  No.  154  of  the  Amer- 
ican Railway  Engineering  Association,  Vol.  14  (Feb.,  1913),  page  850,  which  in 
turn  is  obtained  from  U.  S.  Government  Specifications. 

(2)  The  specifications  referred  to  above  are  as  follows  :  The  pitch  shall  be 
straight  run  residue  obtained  from  the  distillation  of  coal  tar  and  shall  meet 
the  following  requirements  : 

(A)  Melting  point:   135-155°  F. 

(B)  Matter  insoluble  in  benzol:   15-35%. 

(C)  Sp.  gr.  at  60°  F.:   1.25-1.35. 

(D)  Evaporation  loss,  seven  hours,  at  325°  F.:  Maximum  9%  for  pitch  of 
145-155°  F.  m.p.,  and  11%  for  pitch  of  135-145°  m.p. 

(E)  Sp.  gr.  of  distillate  to  670°  F.:  Minimum  1.07,  determined  at  140°  F. 
as  compared  with  water  at  140°  F. 

BITUMINOUS  AND  ASPHALTIC  ROAD  BINDERS 

General.  —  Asphalt  road  binders  are  generally  bought  by 
specification  which  prescribes  the  method  of  testing.  Unless 
otherwise  specified,  however,  the  following  procedures  should  be 
employed  : 


538  TECHNICAL  METHODS  OF  ANALYSIS 

Water. — Weigh  out  approximately  10  grams  of  material  on  a 
filter  paper,  place  the  whole  in  a  300  cc.  Erlenmeyer  flask  and 
determine  the  water  by  the  Xylol  Method  as  described  on  page  271. 

Specific  Gravity. — Determine  the  sp.  gr.  at  25°/25°  C.  by  one 
of  the  following  methods,  depending  upon  the  consistency  of  the 
sample. 

(A)  HYDROMETER  METHOD  (FOR  THIN,  FLUID  MATERIALS). — 
Bring  the  material  to  25°  C.  in  a  hydrometer  cylinder,  place  the 
hydrometer  in  it,  and  when  it  comes  to  rest,  take  the  reading.     In 
case  the  hydrometer  sinks  slowly,  give  it  sufficient  time  to  come  to  a 
definite  resting  point.     Check  this  point  by  raising  the  hydrometer 
and  letting  it  sink  a  second  time.     Never  push  the  hydrometer 
below  the  point  at  which  it  naturally  comes  to  rest  until  the 
last  reading  has  been  taken.     Then  push  below  the  reading  for  a 
distance  of  3  or  4  small  scale  divisions,   whereupon  it  should 
immediately  begin  to  rise.     If  it  fails  to  do  so,  the  material  is 
too  viscous  for  the  hydrometer  method. 

The  direct  sp.  gr.  reading  thus  obtained  is  based  on  water  at 
15.5°  C.  as  unity.  To  correct  to  water  at  25°  C.  multiply  by  1.002. 

(B)  PYCNOMETER  METHOD  (FOR  Viscous  AND  SEMI-SOLID  MA- 
TERIALS).— Use  a  special  pycnometer  of  the  Hubbard  type.     First 
weigh  the  clean,  dry  pycnometer  empty.     Call  this  A.     Fill  with 
freshly  boiled  distilled  water  at  25°  C.  and  again  weigh.  Call  this  B. 
Bring  the  material  to  a  fluid  condition  with  the  least  possible 
heating  and  pour  into  the  dry  pycnometer,  which  may  also  be 
warmed,  and  fill  J  to  f  full  without  allowing  the  material  to  touch 
the  sides  of  the  tube  above  the  desired  level.     Cool  to  room  tem- 
perature and  weigh  with  the  stopper.     Call  this  C.     Then  pour 
in  distilled  water  at  25°  C.  until  the  pycnometer  is  full.     Insert  the 
stopper  and  cool  the  whole  to  25°  C.  by  immersing  completely  for 
one-half  hour  in  a  beaker  of  distilled  water  at  this  temperature. 
Remove  all  surplus  moisture  with  a  soft  cloth  and  weigh.     Call 
this  D.     Calculate  the  sp.  gr.  of  the  material  by  the  following 
formula: 

25°  C.  C-A 

SP.  gr.  at2^5;=(B_A)_(D_c)- 

Results  by  this  method  should  be  accurate  to  0.002. 

NOTE. — The  sp.  gr.  of  fluid  material  may  be  determined  in  the  ordinary 


MISCELLANEOUS  ANALYSES  539 

manner  by  completely  filling  the  pycnometer  with  the  material  and  dividing 
the  weight  of  material  taken  by  that  of  an  equal  volume  of  water. 

(C)  DISPLACEMENT  METHOD  (FOR  HARD,  SOLID  MATERIALS). — 
For  materials  which  are  hard  enough  to  be  broken  and  handled 
in  fragments  at  room  temperature,  weigh  a  small  piece  suspended 
by  means  of  a  silk  thread  from  the  hook  on  the  balance  arm  about 
1.5  inches  above  the  pan.  Call  this  weight  A.  Then  weigh 
immersed  in  water  at  25°  C.  by  placing  a  beaker  about  two-thirds 
full  of  water  on  a  support  over  the  balance  pan,  but  not  touching  it. 
Call  this  weight  B.  Calculate  from  the  formula: 


'  Penetration  Test. — Determine  the  penetration  with  a  standard 
No.  2  Roberts  needle,  acting  for  five  seconds  under  a  total  load 
of  100  grams,  the  temperature  of  the  material  being  at  77°  F., 
and  report  results  in  terms  of  hundredths  of  a  centimeter,  avoiding 
decimals. 

(A)  APPARATUS. — The  standard  needle  is  made  from  round, 
polished,  annealed  steel  drilling  rod,  diameter  0.0405-0.0410  inch. 
The  rod  is  tapered  to  a  sharp  point  at  one  end  with  the  taper 
extending  back  0.25  inch. 

The  container  for  holding  the  material  is  a  flat-bottom  cylin- 
drical dish  2j^  inches  in  diameter  and  If  inches  deep  (this  require- 
ment is  fulfilled  by  American  Can  Company's  Gill  style  3-ounce 
ointment  box,  deep  pattern). 

The  penetration  apparatus  consists  of  a  standard  needle 
inserted  in  a  short  brass  rod,  which  in  turn  is  held  in  the  aluminum 
rod  of  the  apparatus  by  a  binding  screw.  The  frame,  aluminum 
rod  and  needle  weigh  50  grams  without  any  weight  on  the  bottom 
of  the  frame.  For  test  with  100-gram  load  put  on  the  50-gram 
weight. 

(B)  PROCEDURE. — Warm  the  sample  sufficiently  to  flow  and 
pour  it  into  the  tin  box  to  a  depth  of  not  less  than  f  inch.  Transfer 
to  a  glass  crystallizing  dish  or  other  suitable  dish-  and  cover  with  as 
much  water  at  77°  F.  as  convenient  without  spilling.  Let  cool 
one-half  hour  at  room  temperature  protected  from  dust,  then 
immerse  in  water  at  exactly  77°  F.,  and  keep  at  that  temperature^ 


540  TECHNICAL  METHODS  OF  ANALYSIS 

one  and  one-half  hours.  Place  the  dish  containing  the  tin  holder 
with  the  material  on  the  shelf  of  the  machine;  make  sure  that  the 
binding  screw  of  the  needle  holder  is  tight  and  that  the  tin  dish  is 
firm  so  that  no  rocking  motion  can  occur;  lower  the  rod  until  the 
point  of  the  needle  almost  touches  the  surface  of  the  sample; 
finally  very  cautiously  adjust  until  the  needle  point  just  comes  in 
contact  with  the  surface  of  the  sample.  This  can  best  be  seen  by 
having  a  light  so  situated  that  upon  looking  through  the  sides  of 
the  glass  cup,  the  needle  will  be  reflected  from  the  surface  of  the 
sample.  After  thus  setting  the  needle,  move  the  counterweight 
slowly  until  the  foot  of  the  rack  rests  on  the  head  of  the  rod  and 
take  the  reading  of  the  dial.  With  one  hand  open  the  clamp  by 
pressing  the  button  and  with  the  other  hand  start  the  chronometer. 
At  the  end  of  exactly  five  seconds  release  the  clamp,  lower  the 
rack  until  it  rests  on  top  of  the  rod  and  again  read  the  dial.  The 
difference  between  the  first  and  second  readings  in  hundredths  of  a 
centimeter  is  the  penetration  under  the  above  conditions. 

Make  at  least  three  tests  on  points  on  the  surface  of  the  sample 
not  less  than  f  inch  from  the  side  of  the  container  and  not  less  than 
|  inch  apart.  After  each  test  return  the  sample  and  dish  to  the 
water  bath  at  77°  F.,  and  carefully  wipe  the  needle  toward  its  point 
with  a  clean,  dry,  cloth  to  remove  all  adhering  asphalt.  The 
penetration  reported  shall  be  average  of  at  least  three  tests  whose 
values  do  not  differ  by  more  than  four  points. 

NOTES. — (1)  The  point  of  the  needle  should  be  examined  from  time  to  time 
with  a  magnifying  glass  to  see  that  it  is  not  injured  in  any  way.  If  it  is  found 
defective  it  may  be  removed  by  heating  the  brass  rod  and  withdrawing  with 
pliers.  A  new  needle  may  then  be  inserted  in  the  heated  brass,  and  held 
firmly  in  place  by  a  drop  of  soft  solder. 

(2)  A  cup  suitable  for  holding  the  box  containing  the  test  material  during 
penetration  is  conveniently  made  from  a  glass  crystallizing  dish  4  inches  in 
diameter  with  straight  sides  about  2.5  inches  high.  Three  right  triangles, 
with  right  angle  sides  0.4  and  2  inches,  respectively,  are  cut  from  ^  inch  sheet 
metal,  some  solid  bitumen  is  melted  in  the  bottom  of  the  dish  forming  a  layer 
about  |  inch  thick,  into  which  the  triangles  are  placed,  resting  on  the  side  2 
inches  long.  Their  apexes  should  meet  the  center  with  their  short  sides  divid- 
ing the  circumference  of  the  dish  into  three  equal  parts.  When  the  bitumen 
is  hardened,  the  triangles  give  a  firm  support  for  the  circular  boxes  and  the 
possibility  of  any  rocking  motion,  and  consequent  faulty  results,  is  avoided 

Volatility. — Weigh  out  about  50  grams  of  sample  in  a  tin  box 
inches  in  diameter  by  about  If  inches  deep  (3  ounce  Gill  style 


MISCELLANEOUS  ANALYSES  541 

ointment  box,  deep  pattern),  first  carefully  weighing  the  box; 
then  adjust  the  weight  of  sample  so  that  it  does  not  vary  more 
than  0.2  gram  from  50.  It  may  be  necessary  to  warm  some  of  the 
material  in  order  to  handle  it  conveniently,  after  which  it  must 
be  allowed  to  cool  before  determining  the  accurate  weight. 

Before  making  the  test,  the  interior  of  the  oven  should  show  a 
temperature  of  163°  C.  (325°  F.).  Heat  the  material  in  the 
oven  for  five  hours,  remove,,  cool  in  a  desiccator  and  weigh.  Cal- 
culate the  per  cent  loss. 

NOTES. — (1)  For  strictly  accurate  work  the  New  York  Testing  Laboratory 
oven  should  be  used.  (See  U.  S.  Dept.  of  Agriculture,  Bulletin  314,  page  19.) 

(2)  In  case  it  is  not  desired  to  determine  the  penetration  of  the  residue, 
tests  should  be  run  on  20  grams  of  material  in  a  tin  container,  6  cm.  in  diam- 
eter by  2  cm.  deep.  In  any  case,  the  amount  of  material  taken  should  be 
stated. 

Float  Test. — This  test  is  always  made  on  viscous  and  semi- 
solid  refined  tars  and  often  on  viscous  and  semi-solid  petroleum 
and  asphalt  products,  although,  when  penetration  tests  can  be 
employed  on  the  latter,  the  float  test  is  not  always  considered 
necessary.  For  more  fluid  products  make  the  tests  at  32°  C.; 
for  semi-solid  materials,  at  50°  C.;  and  in  certain  cases,  on  unusu- 
ally hard  materials,  at  100°  C. 

The  float  apparatus  consists  of  2  parts,  an  aluminum  float 
or  saucer  and  a  conical  brass  collar.  Place  the  brass  collar  with 
the  small  end  down  on  a  brass  plate  previously  amalgamated  with 
Hg  by  rubbing  it  first  with  a  dilute  solution  of  mercuric  chloride 
or  nitrate  and  then  with  Hg.  Heat  a  small  quantity  of  the  mate- 
rial in  a  metal  spoon  until  fluid,  taking  care  that  it  suffers  no  appre- 
ciable loss  by  volatilization  and  that  it  is  kept  free  from  air  bubbles. 
Pour  into  the  collar  in  a  thin  stream  until  slightly  more  than  level 
with  the  top.  Cool  to  room  temperature  and  remove  the  surplus 
with  a  spatula  which  has  been  slightly  heated.  Place  the  collar 
and  plate  in  ice  water  at  about  5°  C.  for  at  least  fifteen  minutes. 
Meanwhile  place  a  500  cc.  cup  or  beaker,  nearly  filled  with  water, 
over  a  flame  and  heat  to  the  test  temperature.  At  the  end  of 
fifteen  minutes  or  more  remove  the  collar  with  contents  from  the 
brass  plate  and  screw  into  the  aluminum  float,  taking  care  to 
screw  it  in  as  far  as  it  will  go..  Float  the  apparatus  on  the  sur- 
face of  the  water,  at  the  same  instant  starting  a  stop  watch. 


542  TECHNICAL  METHODS  OF  ANALYSIS 

When  water  first  breaks  through  the  plug  of  bituminous  material, 
stop  the  watch.  The  time  in  seconds  between  placing  the  appa- 
ratus on  the  water  and  when  the  water  breaks  through  is  the 
"  float  test." 

Flash  Point. — Determine  the  flash  point  in  the  open  cup  tester 
as  described  on  page  255. 

Softening  Point. — Bituminous  materials  have  no  true  melting 
point.  Any  method  of  determining  the  "  melting  point "  of 
these  materials  must  be  arbitrary.  The  two  in  most  common 
use  are  the  following : 

(1)  CUBE  METHOD  (Not  applicable  to  pitches  having  a  melting 
point  above  77°  C.). — First  melt  the  material  in  a  spoon  by  gentle 
application  of  heat  until  sufficiently  fluid  to  pour  readily,  taking 
care  that  it  suffers  no  appreciable  loss  by  volatilization.  Stir 
thoroughly,  avoiding  incorporating  air  bubbles  in  the  mass.  Then 
pour  into  an  0.5  inch  brass  cubical  mold,  which  has  been  amal- 
gamated with  Hg,  and  which  is  placed  on  an  amalgamated  brass 
plate.  The  brass  may  be  amalgamated  by  washing  it  first  with  a 
dilute  solution  of  mercuric  chloride  or  nitrate,  after  which  the  Hg  is 
rubbed  into  the  surface.  By  this  means  the  bitumen  is  to  a  con- 
siderable extent  prevented  from  sticking  to  the  sides  of  the  mold. 
The  hot  material  should  slightly  more  than  fill  the  mold,  and  when 
cooled  the  excess  should  be  cut  off  with  a  slightly  heated  spatula. 

(A)  Pitches  having  softening  points  between  J$  and  77°  C.— 
Fill  a  600  cc.  low  form  Griffin  beaker  to  a  depth  of  about  3.75 
inches  with  freshly  boiled  distilled  water  at  15.5°  C.  Place  the 
cube  of  pitch  on  an  L-shaped  right-angled  hook  made  of  No.  12 
B.  &  S.  gauge  copper  wire.  The  foot  of  the  L  should  be  1  inch 
long  and  should  run  through  the  center  of  the  cube  so  that  one 
edge  of  the  cube,  not  its  surface,  is  parallel  to  the  bottom  of  the 
beaker  and  exactly  1  inch  above  it.  The  upper  edge  of  the  cube 
should  be  2  inches  below  the  surface  of  the  water.  Let  it  remain 
in  the  water  for  fifteen  minutes  before  applying  heat  to  the  beaker 
set  on  a  wire  gauze.  Suspend  the  thermometer  so  that  the  bottom 
of  the  bulb  is  level  with  the  bottom  edge  of  the  cube  and  within 
0.25  inch  of  but  not  touching  the  cube. 

Apply  heat  so  that  the  temperature  of  the  water  is  raised 
5°  C.  (9°  F.)  per  minute.  The  rate  of  rise  must  be  uniform  and 
should  not  be  averaged  over  the  period  of  test,  The  maximum 


MISCELLANEOUS  ANALYSES  543 

permissible  variation  for  any  minute  period  after  the  first  three 
minutes  is  ±0.5°  C.  (1°  F.).  If  the  rate  of  rise  exceeds  this 
limit,  the  test  must  be  rejected. 

The  temperature  recorded  by  the  thermometer  at  the  instant 
the  pitch  touches  the  bottom  of  the  beaker  is  the  softening  point 
of  the  sample. 

NOTES. — (1)  The  burner  should  be  protected  by  a  shield  to  avoid  draft. 

(2)  The  use  of  freshly  boiled  distilled  water  is  essential  to  prevent  air  bub- 
bles forming  on  the  cube  and  retarding  sinking. 

(3)  Rigid  adherence  to  the  prescribed  rate  of  heating  is  absolutely  essential 
for  accuracy. 

(4)  A  sheet  of  paper  placed  on  the  bottom  of  the  beaker  and  weighted  down 
will  prevent  the  pitch  from  sticking  to  the  glass  and  save  considerable  time  and 
trouble  in  cleaning. 

(5)  The  limit  of  accuracy  of  the  test  is  ±0.5°  C.  (1°  F.). 

(6)  The  thermometer  should  be  graduated  from  0-80°  C.,  preferably  in 
J°  divisions  and  the  top  of  the  mercury  column  at  the  time  of  reading  should 
be  above  the  surface  of  the  water. 

(B)  Pitches  having  softening  points  below  43°  C. — Use  the  same 
method  as  given  above,  except  that  the  water  when  placed  in  the 
beaker  should  be  at  a  temperature  of  4°  C.  instead  of  15.5°  C. 
Let  the  cube  remain  fifteen  minutes  in  this  water  before  applying 
heat. 

(2)  RING  AND  BALL  METHOD. — (A)  Apparatus. — This  consists 
of  a  brass  ring  exactly  f  inch  in  diameter,  J  inch  deep,  and  ^  inch 
wall,  suspended  exactly  1  inch  above  the  bottom  of  a  beaker;  a 
steel  ball  |  inch  in  diameter,  weighing  between  3.45  and  3.55 
grams;  a  standardized  thermometer;  and  a  low  form  Griffin  glass 
beaker  of  about  600  cc.  capacity. 

(B)  Procedure. — Carefully  melt  the  sample,  as  in  the  Cube 
Method  above,  and  fill  the  ring  with  excess  of  the  material  to  be 
tested.  During  filling,  rest  the  ring  on  amalgamated  brass  to 
prevent  sticking.  After  cooling,  remove  the  excess  with  a  slightly 
heated  spatula.  Fill  the  beaker  to  a  depth  of  about  3.25  inches 
with  freshly  boiled  distilled  water  at  5°  C.*  Place  the  ball  in  the 
center  of  the  upper  surface  of  the  material  and  suspend  in  water  so 
that  the  lower  surface  of  the  filled  ring  is  exactly  1  inch  above  the 
bottom  of  the  beaker  and  the  upper  surface  is  2  inches  below  the 

*  For  materials  having  a  softening  point  above  90°  C.  use  glycerine  instead 
of  water. 


544  TECHNICAL  METHODS  OF  ANALYSIS 

surface  of  the  water.  Let  remain  in  the  water  for  fifteen  minutes 
before  applying  heat.  Suspend  the  thermometer  so  that  the 
bottom  of  the  bulb  is  level  with  the  bottom  of  the  ring  and  within 
0.25  inch  of,  but  not  touching,  the  ring.  Apply  heat  uniformly,  so 
that  the  temperature  of  the  water  rises  5°  C.  (9°  F.)  per  minute. 
The  rate  of  rise  must  be  uniform  and  is  not  to  be  averaged  over  the 
period  of  test.  The  maximum  permissible  variation  for  any 
minute  period  after  the  first  three  shall  be  ±0.5°  C.  (1°  F.). 
Reject  any  tests  where  the  rate  of  rise  exceeds  these  limits.  The 
temperature  recorded  by  the  thermometer  at  the  instant  the 
sample  touches  the  bottom  of  the  beaker  is  its  softening  point. 
(See  notes  under  Cube  Method  above.) 

Total  Bitumen  (Soluble  in  Carbon  Bisulfide). — Prepare  a 
Gooch  crucible  (the  best  size  is  1.75  inch  at  the  top,  1  inch  deep, 
and  1.5  inch  at  the  bottom)  with  an  asbestos  mat  which  will  just 
show  light  through  it.  Suck  dry,  heat  a  few  minutes  in  the  oven, 
ignite  over  a  Tirrill  burner,  cool  in  a  desiccator  and  weigh. 
Place  1-10  grams  of  the  sample,  depending  upon  the  amount  of 
insoluble  matter,  in  a  150  cc.  Erlenmeyer  flask,  which  has  been 
previously  weighed,  and  weigh  accurately;  then  pour  100  cc. 
of  CS2  into  the  flask  in  small  portions  with  continual  agitation 
until  all  lumps  disappear  and  nothing  adheres  to  the  bottom. 
Cork  and  set  aside  for  fifteen  minutes  or  longer.  Decant  the  CS2 
solution  very  carefully  through  the  asbestos  in  the  Gooch  crucible 
without  suction,  with  care  not  to  stir  up  any  precipitate.  At  the 
first  sign  of  any  sediment  coming  over,  stop  the  decantation,  and 
let  the  filter  drain.  Wash  a  small  amount  of  CS2  down  the  sides 
of  the  flask,  bring  the  precipitate  upon  the  mat  and  remove  all 
adhering  matter  from  the  flask  to  the  crucible  with  a  policeman 
which  is  not  attacked  by  CS2.  Wash  the  contents  of  the  crucible 
with  CS2  until  washings  are  colorless.  Apply  suction  until  no 
odor  of  CS2  remains.  Clean  the  outside  of  the  crucible  with  a 
soft  cloth  moistened  with  a  little  CS2.  Dry  at  100°  C.  for  about 
twenty  minutes,  cool  in  a  desiccator  and  weigh.  (If  any  appre- 
ciable amount  of  insoluble  matter  adheres  to  the  flask,  it 
should  also  be  dried  and  weighed  and  any  increase  over  the 
original  weight  added  to  that  of  the  insoluble  matter  in  the 
crucible.) 

The   total   weight   of  insoluble   material   may   include   both 


MISCELLANEOUS  ANALYSES  545 

organic  and  mineral  matter.  Ignite  at  a  red  heat  until  no  incan- 
descent particles  remain.  Cool  and  weigh  the  mineral  matter. 
Report  the  difference  between  the  total  weight  of  material  insoluble 
in  CS2  and  the  weight  of  the  substance  taken  (both  expressed 
in  percentages)  as  "  total  bitumen."  Also  report  the  per  cent 
of  mineral  matter  as  "  ash." 

NOTES. — (1)  In  certain  natural  asphalts  it  is  practically  impossible  to 
retain  all  finely  divided  mineral  matter  on  an  asbestos  mat.  It  is,  therefore, 
generally  more  accurate  to  obtain  the  result  for  total  mineral  matter  by  direct 
ignition  of  1  gram  in  a  platinum  crucible  or  to  use  the  result  for  ash  obtained 
in  the  fixed  carbon  test.  Then  determine  the  total  bitumen  by  deducting 
from  100%  the  sum  of  the  per  cent  of  total  mineral  matter  and  of  organic 
insoluble  matter.  If  the  presence  of  carbonate  mineral  is  suspected,  the  per 
cent  of  mineral  matter  may  be  most  accurately  determined  by  treating  the 
ash  from  the  fixed  carbon  determination  with  a  few  drops  of  ammonium  car- 
bonate solution,  drying  at  100°  C.,  then  heating  for  a  few  minutes  at  dull  red 
heat,  cooling  and  weighing  again. 

(2)  When  unusual  difficulty  in  filtering  is  experienced,  it  is  necessary  to  let 
stand  much  longer  than  fifteen  minutes.     In  such  cases  it  is  preferable  to 
proceed  as  follows: 

Weigh  2-15  grams  (depending  on  richness  in  bitumen)  into  a  150  cc. 
Erlenmeyer  flask,  which  .has  been  previously  weighed,  and  treat  with  100  cc. 
of  082.  Cork  the  flask  loosely  and  shake  from  time  to  time,  until  practically 
all  large  particles  have  been  broken  up.  Set  aside  undisturbed  for 
forty-eight  hours.  Decant  the  solution  into  a  similar  flask  that  has  been 
previously  weighed,  as  much  of  the  solvent  being  poured  off  as  possible  with- 
out disturbing  the  residue.  Treat  the  first  flask  again  with  fresh  082,  and 
shake  as  before.  Put  away  with  the  second  flask  undisturbed  for  forty-eight 
hours. 

At  the  end  of  this  time  carefully  decant  off  the  contents  of  the  two  flasks 
upon  a  weighed  Gooch  crucible  fitted  with  an  asbestos  filter,  the  contents  of 
the  second  flask  being  passed  through  the  filter  first.  The  asbestos  filter 
should  be  made  of  ignited  long-fiber  amphibole,  packed  in  the  bottom  of  the 
Gooch  crucible  to  a  depth  of  not  over  ^  inch.  After  passing  the  contents  of 
both  flasks  through  the  filter,  shake  the  two  residues  with  more  fresh  CS2 
and  set  aside  for  twenty-four  hours  without  disturbing,  or  until  good  subsida- 
tion  has  taken  place.  Again  decant  the  solvent  off  upon  the  filter.  Con- 
tinue this  washing  until  filtrate  or  washings  are  practically  colorless. 

•  Dry  the  crucible  and  both  flasks  at  125°  C.  and  weigh.  Evaporate  the 
filtrate  containing  the  bitumen,  burn  the  bituminous  residue,  and  add  the 
weight  of  ash  thus  obtained  to  that  of  the  residue  in  the  two  flasks  and  cruci- 
ble. The  sum  of  these  weights  deducted  from  the  weight  of  substance  taken 
gives  the  weight  of  bitumen  extracted. 

(3)  In  the  analysis  of  tars  the  insoluble  organic  matter  is  commonly 
known  and  reported  as  "free  carbon." 


546  TECHNICAL  METHODS  OF  ANALYSIS 

Bitumen  Insoluble  in  86°  Naphtha. — This  determination  is 
made  in  the  same  general  way  as  the  Total  Bitumen,  using  instead 
of  C&2  100  cc.  of  naphtha,  at  least  85%  of  which  distills  between 
35  and  65°  C.  It  is  advisable  to  heat  the  sample  after  it  has  been 
weighed  into  the  flask  and  let  it  cool  in  a  thin  layer  around  the 
lower  part.  Not  more  than  half  the  total  amount  of  naphtha 
required  should  be  used  until  the  sample  is  entirely  broken  up; 
then  add  the  remainder,  swirl  the  flask,  mix  thoroughly,  cork  and 
set  aside  thirty  minutes  or  more.  In  making  the  filtration  use 
the  utmost  care  to  avoid  stirring  up  any  of  the  precipitate,  and 
make  the  first  decantation  as  complete  as  possible.  Suction  may 
be  applied  when  filtration  by  gravity  almost  ceases,  but  should 
be  used  sparingly  as  it  tends  to  clog  the  filter.  The  material  on 
the  felt  should  never  be  allowed  to  run  dry  until  washing  is  com- 
pleted as  shown  by  a  colorless  filtrate.  When  considerable 
insoluble  matter  adheres  to  the  flask,  make  no  attempt  to  remove 
it  completely,  merely  wash  until  free  from  soluble  matter  and  dry 
the  flask  (after  removing  naphtha)  for  about  one  hour  at  100°  C., 
after  which  cool  and  weigh.  The  per  cent  of  bitumen  insoluble 
in  naphtha  is  reported  upon  the  basis  of  the  total  bitumen  taken 
as  100. 

NOTE. — The  difference  between  the  amounts  insoluble  in  CS2  and  in  naph- 
tha is  the  bitumen  insoluble  in  naphtha.  If,  for  instance,  the  insoluble  in 
CS2  is  1%  and  the  total  insoluble  in  naphtha  is  10.9%,  the  calculation  of  % 
bitumen  insoluble  in  naphtha  is  as  follows: 

Bit,  insol.  in  naphtha     10.9-1  _  9.9 
Total  bitumen       ~  100-1~  99~ 

Fixed  Carbon  and  Ash. — Determine  fixed  carbon  and  ash  on 
1  gram  as  in  Coal,  page  174.  (See  also  under  Total  Bitumen 
above.) 

Distillation. — From  the  sp.  gr.  of  the  material  calculate  the 
weight  of  100  cc.  and  pour  this  amount  into  a  tared  250  cc.  Engler 
distillation  flask,  after  warming  in  a  tin  cup  if  necessary  to  make  it 
sufficiently  fluid.  For  the  procedure  in  distilling  and  apparatus 
used  see  page  551.  Report  results  both  as  per  cent  by  weight 
and  by  volume,  or  as  required. 

Ductility. — Form  a  briquette  of  the  sample  by  pouring  the 
molten  material  into  a  briquette  mould.  The  dimensions  of  the 


MISCELLANEOUS  ANALYSES  547 

briquette  shall  be:  1  cm.  (0.394  inch)  in  thickness  throughout  its 
entire  length;  distance  between  clips  or  end  pieces,  3  cm.;  width 
of  asphalt  cement  section  at  mouth  of  clips,  2  cm. ;  width  at  min- 
imum cross-section,  half-way  between  clips,  1  cm.  The  center 
pieces  are  removable,  the  briquette  mold  being  held  together 
during  molding  with  a  clamp  or  wire. 

The  molding  of  the  briquette  is  to  be  done  as  follows:  The 
two  center  sections  must  be  well  amalgamated  to  prevent  the 
sample  from  adhering  to  them.  Then  place  the  briquette  mold 
on  a  freshly  amalgamated  brass  plate.  Pour  the  sample  to  be 
tested,  while  in  a  molten  state,  into  the  mold,  adding  a  slight 
excess  to  allow  for  shrinkage  on  cooling.  When  the  material 
in  the  mold  is  nearly  cool,  cut  off  the  briquette  level  with  a  warm 
knife  or  spatula.  When  thoroughly  cooled  to  the  proper  tem- 
perature, remove  the  clamp  and  the  two  side  pieces,  leaving  the 
briquette  held  at  each  end  by  the  ends  of  the  mold,  which  now 
play  the  part  of  clips.  Keep  the  briquette  in  water  for  thirty 
minutes  at  4°  C.  (39°  F.)  or  25°  C.  (77°  F.)  before  testing,  depend- 
ent on  the  temperature  at  which  the  ductility  is  desired.  Place 
the  briquette  with  clips  attached  in  the  ductility  test  machine, 
filled  with  water  at  one  of  the  above  temperatures  to  a  sufficient 
height  to  cover  the  briquette  not  less  than  5  cm.  (1.97  in.).  The 
machine  consists  of  a  rectangular  water-tight  box,  having  a  mov- 
able block  working  on  a  worm  gear  from  left  to  right.  The  left 
clip  is  held  rigid  by  placing  its  ring  over  a  short  metal  peg  pro- 
vided for  this  purpose;  the  right  clip  is  placed  over  a  similar  rigid 
peg  on  the  movable  block.  The  latter  is  provided  with  a  pointer 
which  moves  along  a  centimeter  scale.  Before  starting  the  test, 
adjust  the  centimeter  scale  with  the  pointer  at  zero.  Then  apply 
power  by  the  worm  gear,  pulling  from  left  to  right  at  a  uniform 
rate  of  5  cm.  per  minute.  The  distance  in  centimeters  reg- 
istered by  the  pointer  on  the  scale  at  the  time  of  rupture  of 
the  thread  of  asphalt  material  is  taken  as  the  ductility  of  the 
material. 

Paraffin  Scale. — The  determination  of  paraffin  scale  is 
seldom  required.  The  procedure  is  described  in  U.  S.  Dept  of 
Agriculture,  Bulletin  314,  page  32. 

Petroleum  or  Asphalt  Products  in  Tar. — Take  fractions  of 
the  distillation  from  270-300°  C.,  from  300-350°  C.,  and  from 


548  TECHNICAL  METHODS  OF  ANALYSIS 

350-375°,  C.  respectively.     Stir  each  fraction  separately  and,  if 
necessary,  warm  to  dissolve  any  solids. 

To  4  cc.  of  each  fraction  in  tubes  graduated  to  0.1  cc.  add  6  cc. 
of  dimethyl  sulfate.  Shake  well  and  let  stand  thirty  minutes. 
Read  off  the  volume  of  any  oil  separating  on  top  of  the  liquid. 
This  is  due  to  asphalt  or  petroleum  products.  Calculate  the  vol- 
ume per  cent  in  each  fraction  and  report  as  follows : 


Fractions 
°C. 

Per  Cent  Distillate 

Per  Cent  Distillate 
Insoluble  in  Dimethyl 
Sulfate 

270-300 
300-350 

350-375 

The  test  is  mainly  qualitative  but  will  indicate  as  little  as 
3%  of  petroleum  or  asphalt  products  in  tar. 

REFERENCES. — Sp.  gr.,  flash  point,  float  test,  penetration,  melting  point 
(Cube  method)  and  bitumen:  U.  S.  Dept.  of  Agriculture,  Bulletin  314. 

Melting  point  (Ring  and  Ball  method):  American  Soc.  for  Testing 
Materials,  Proceedings  1916,  page  549. 

Volatility:  U.  S.  Dept.  of  Agriculture,  Bulletin  314,  page  19  and  Bulletin 
555,  page  36. 

Ductility  and  Paraffin:  Am.  Soc.  Civil  Eng.,  1914,  Proceedings,  pages 
3047  and  3049. 

See  also  articles  by  J.  M.  Weiss  in  J.  Ind.  Eng.  Chem.,  1918,  "  Methods  of 
Analysis  used  in  the  Coal  Tar  Industry." 


CRUDE  COAL-TAR  AND  WATER-GAS  TAR 

General. — The  analysis  of  crude  coal  and  water-gas  tars  gen- 
erally involves  the  following  determinations:  Specific  gravity, 
free  carbon,  water,  fractional  distillation,  and  tar  acids. 

Sampling. — Tar  is  best  sampled  when  being  unloaded  from  the 
tank  car  or  barge.  A  pet  cock,  with  a  nipple  projecting  about  one- 
third  of  its  diameter,  should  be  placed  in  the  pipe  line  and  a  con- 
tinuous stream  of  tar  drawn  off  into  a  barrel  during  the  time  of 
unloading.  The  pet  cock  should  be  so  regulated  that  the  sample 
will  represent  approximately  0.1%  of  the  shipment.  The  tar  may 


MISCELLANEOUS  ANALYSES  549 

then  be  stirred  up  and  a  sample  taken  from  the  barrel.     Samples 
of  tar  should  be  placed  in  heavy  clear  bottles  or  screw  top  tin  cans. 

When  necessary  to  sample  from  storage  tanks,  or  wells,  it 
should  be  done  by  means  of  a  "  thief."  This  is  particularly 
necessary  when  different  shipments  of  tar  of  widely  different 
gravities  have  been  run  into  the  same  tank.  A  simple  and  efficient 
apparatus  may  be  made  from  a  piece  of  2-in.  pipe  provided  with  a 
lever  handle  cock.  This  may  be  closed  by  means  of  a  small  iron 
rod.  By  cutting  away  part  of  the  cock  and  half  of  the  plug,  an 
opening  nearly  as  large  as  the  interior  of  the  pipe  is  produced. 
In  taking  the  sample,  the  cock  is  opened  and  the  "  thief  "  lowered 
slowly  to  the  bottom  of  the  tank,  well,  or  car,  the  "  thief  "  having 
previously  been  rinsed  with  the  liquid  to  be  sampled.  The  cock 
is  then  closed,  the  "  thief  "  is  withdrawn,  and  the  sample  run  into 
a  bottle.  This  operation  is  repeated  until  a  sample  of  about  1 
gallon  is  obtained,  after  which  the  contents  should  be  thoroughly 
mixed  and  a  portion  taken  to  serve  as  a  smaller  sample  for  analysis. 

It  should  be  noted  that  this  method  cannot  be  used  with 
horizontal  cylindrical  tanks. 

In  the  case  of  tar  where  there  is  always  a  certain  amount  of 
water  or  ammoniacal  liquor  floating  on  the  surface,  it  seems  best 
to  attempt  to  locate  the  level  of  the  water  or  liquor,  taking  a  sample 
at  this  point,  and  then  sample  a  lower  portion  of  the  tar  which  is 
reasonably  free  from  water,  and  by  calculation,  estimate  the  total 
quantity  of  water  present. 

Specific  Gravity.— The  sp.  gr.  of  thin  tar,  such  as  water-gas 
tar,  free  from  water,  may  be  determined  by  the  Westphal  balance. 
The  measurements  should  be  made  at  25°  C.  where  possible. 
If  this  is  not  possible,  correct  from  the  observed  temperature  to 
25°  C.  as  follows: 

Take  the  reading  with  the  Westphal  balance  at  the  tempera- 
ture t°  C.  Balance  the  plummet  in  distilled  water  at  the  same 
temperature  and  take  the  reading.  Divide  the  first  reading  by 
the  second.  This  is  the  sp.  gr.  of  the  material  at  t°  C. 

If  t°  is  greater  than  25°,  then 
Sp.  gr.  at   25°  C.  =  sp.  gr.  at  t°  C.+ 0.00068 (Z-25). 

In  case  t°  is  less  than  25°,  then 
Sp.  gr.  at  25°  C.  =  sp.  gr.  at  t°  C.- 0.00068  (25- 1). 

A  hydrometer  may  be  used  in  place  of  the  Westphal  balance. 


550  TECHNICAL  METHODS  OF  ANALYSIS 

Since  hydrometers  are  standardized  for  water  at  15.5°  C.,  the 
hydrometer  reading  in  the  tar  at  25°  C.  should  be  multiplied  by 
1.002  to  bring  it  to  the  basis  of  H2O  =  1  at  25°  C. 

For  accurate  work  and  for  thick  tars  the  modified  Hubbard's 
sp.  gr.  bottle  should  be  used.  In  using  this  bottle  the  following 
weights  are  necessary  in  the  order  given : 

A  =  Weight  of  empty  bottle; 

B  =  Weight  of  bottle  filled  with  water  to  the  mark  at  25°  C.; 
and    C  =  Weight  of  bottle  filled  with  tar  at  25°  C. ; 

25°  C      C A 

then  sp.  gr.  of  tar  at  r^f  =  ]^[- 

NOTE. — The  Hubbard  method  is  not  accurate  for  tar  containing  water. 
In  such  case  the  tar  should  be  dehydrated,  as  described  below  under  Distilla- 
tion, and  the  sp.  gr.  determined  on  the  dehydrated  tar.  The  sp.  gr.  of  the 
original  tar  may  be  calculated  as  follows : 

Let      A  =  Sp.  gr.  of  dehydrated  tar; 

J3  =  Per  cent  of  H^O  expressed  as  decimal; 
and     X  =  Sp.  gr.  of  original  tar; 
then   X  =  B+A  (1-5). 

Moisture. — For  most  purposes  the  Xylol  Method  is  suitable, 
as  described  on  page  271. 

In  cases  of  dispute,  however,  use  the  method  described  in  the 
Gas  Chemists'  Hand  Book  (1916),  page  191,  as  follows:  Measure 
50  cc.  of  coal-tar  naphtha  or  light  oil  (which  must  be  tested  to 
determine  that  it  is  free  from  water  whenever  a  new  supply  is 
required)  in  a  250  cc.  graduated  cylinder.  Add  200  cc.  of  the  tar, 
transfer  the  contents  of  the  cylinder  to  a  copper  still  (see  below 
under  Distillation)  and  wash  the  cylinder  with  50-75  cc. 
more  of  naphtha,  adding  the  washing  to  the  contents  of  the  still. 
Attach  the  lid  and  clamp,  using  a  paper  gasket.  Distill  through 
a  still  head,  connected  to  a  condenser,  and  collect  the  distillate  in  a 
separatory  funnel  having  a  graduated  stem  to  which  15-20  cc. 
of  benzene  have  been  previously  added.  Apply  heat  to  the  still 
by  means  of  the  ring  burner  and  distill  until  the  temperature  as 
indicated  by  the  thermometer  has  reached  205°  C.  The  bulb  of 
the  thermometer  must  be  opposite  the  side  neck  of  the  still  head. 
The  reading  of  the  volume  of  water  is  made  after  twirling  the  funnel 
and  letting  the  water  settle  for  a  few  minutes.  Figure  the  per 
cent  by  volume. 


MISCELLANEOUS  ANALYSES  551 

Free  Carbon. — Fur  accurate  work  the  tar  should  be  dried 
before  testing  and  after  drying  passed  hot  through  a  30-mesh 
sieve  to  remove  foreign  substances.  This  ordinarily,  however, 
is  not  necessary  as  such  foreign  substances  could  easily  be  detected 
during  analysis. 

From  materials  of  5%  or  more  carbon  take  about  5  grams, 
with  lesser  percentages  take  10  grams  approximately.  Weigh 
out  in  a  100  cc.  beaker  and  digest  with  about  5  cc.  of  c.  p.  toluene 
on  the  steam  bath  for  not  over  thirty  minutes.  If  the  solution  is 
kept  hot  and  constantly  stirred,  digestion  can  be  completed  very 
rapidly. 

Weigh  in  a  weighing  bottle  a  filter  cup  prepared  as  described 
below  and  place  in  a  carbon  filter  tube  over  a  beaker  or  flask. 
Decant  the  toluene  tar  mixture  through  the  thimble  and  wash 
with  hot  toluene  until  clean.  After  transferring  all  the  ma- 
terial from  the  beaker,  wash  once  with  hot  c.  P.  benzene,  drain, 
cover  with  a  cap  of  filter  paper  and  extract  with  benzene  in  an 
extractor  of  the  Cottle  or  Rubber  Insulation  Committee  type  as 
used  in  rubber  analysis  (see  Fig.  25,  page  481).  Continue  extrac- 
tion until  the  descending  benzene  is  colorless;  remove  the  thimble, 
discard  the  cap,  dry  at  105°  C.  and  weigh  in  the  same  weighing 
bottle  as  originally  used.  The  residue  is  carbon.  Report  the 
result  as  "  free  carbon  (toluene-benzene  method)." 

NOTES. — (1)  If  the  carbon  is  contaminated  by  dirt,  ignite  in  a  crucible 
and  weigh  the  inorganic  residue.  Subtract  this  from  the  original  weight  of 
residue. 

(2)  Filter  cups:  The  filter  cups  or  thimbles  are  made  of  15  cm.  hardened 
filter  paper.  To  make  a  cup,  two  circles  should  be  taken  and  one  cut  down 
to  a  diameter  of  about  14  cm.  A  round  stick  about  1  inch  hi  diameter  is  used 
as  a  form.  The  stick  is  placed  in  the  center  of  the  circles  of  filter  paper,  the 
smaller  inside;  the  papers  are  then  folded  symmetrically  round  the  stick  to 
form  a  cup  of  about  2.5  inches  in  length.  After  being  made,  they  are  soaked 
in  benzene  to  remove  any  grease  due  to  handling,  drained,  dried  in  a  steam 
oven  and  kept  in  a  desiccator  until  used. 

Distillation. — (1)  SAMPLING. — The  sample  as  received  must 
be  thoroughly  stirred  and  agitated,  warming,  if  necessary,  to 
insure  complete  mixture  before  the  portion  for  analysis  is  removed. 

(2)  DEHYDRATION. — If  the  presence  of  water  is  suspected  or 
known,  dehydrate  the  material  before  distillation.  Place  about 
£00-400  cc.  in  a  copper  still  (A.  H.  Thomas  Co.;  Catalog  No. 


552  TECHNICAL  METHODS  OF  ANALYSIS 

20416)  provided  with  a  distilling  head  connected  with  a  water- 
cooled  condenser.  Use  a  ring  burner,  starting  with  a  small  flame 
at  the  top  of  the  still,  and  gradually  lowering,  if  necessary,  until 
all  water  has  been  driven  off  and  the  thermometer  reads  170°  C. 
(The  bulb  of  the  thermometer  should  be  opposite  the  side  tube  of 
the  distilling  head.)  Collect  the  distillate  in  a  200  cc.  separatory 
funnel  with  the  tube  cut  off  close  to  the  stopcock.  When  all 
water  has  been  driven  over  and  the  distillate  has  separated  clear, 
draw  off  the  water  and  return  the  oils  to  the  residue  in  the  still. 
(If  crystals  separate,  warm  the  mixture  until  they  go  into  solution.) 
Let  the  contents  of  the  still  cool  to  below  100°  C.  before  the  oils 
are  returned;  stir  well  and  mix  with  the  residue. 

(3)  APPARATUS. — The  apparatus  shall  consist  of  the  following 
standard  parts: 

(a)  Flask. — The  distillation  flask  shall  be  a  250  cc.  Engler 
distilling  flask,  of  the  following  dimensions : 

Diameter  of  bulb 8.0  cm. 

Length  of  neck 15 . 0  cm. 

Diameter  of  neck 1.7  cm. 

Surface  of  material  to  lower  side  of  tubulature 11 .0  cm. 

Length  of  tubulature 15 . 0  cm. 

Diameter  of  tubulature 0.9  cm. 

Angle  of  tubulature 75° 

A  variation  of  3%  from  the  above  measurements  is  allowed. 

(b)  Thermometer. — The    thermometer    shall    be    of    hardened 
glass,  filled  with  inert  gas  under  pressure  and  provided  with  an 
expansion  chamber  at  the  top;  it  shall  read  from  0  to  400°  C.  or 
450°  C.,  shall  be  graduated  in  single  degrees  Centigrade,  and  shall 
have  the  following  dimensions : 

Diameter  of  stem 6.5-7.5  mm.  (approximately). 

Length  of  thermometer. 385  mm. 

Length  from  0°  to  400°  marks 285-305  mm. 

Length  of  bulb 10-15  mm. 

Diameter  of  bulb 5  mm.  and  not  exceeding 

diameter  of  stem. 
Distance  from  zero  to  bottom  of  bulb .       25-35  mm . 

When  the  thermometer  is  taken  at  a  temperature  of  26°  C. 
and  plunged  into  a  free  flow  of  live  steam,  the  meniscus  must  pass 
the  90°  mark  in  not  more  than  six  seconds. 


MISCELLANEOUS  ANALYSES  553 

(c)  Condenser. — The  condenser  tube  shall  have  the  following 
dimensions : 

Length  of  tube 500  mm. 

Width  of  tube 12-15  mm. 

Width  of  adaptor  end  of  tube 20-25  mm. 

(d)  Stands. — Two    iron    stands    are    required,    one    with    a 
universal  clamp  for  holding  the  condenser,  and  one  with  a  light 
grip  arm  with  a  cork-lined  clamp  for  holding  the  flask. 

(e)  Burner  and  shield. — The  Bunsen*  burner  shall  be  provided 
with  a  tin  shield  20  cm.  long  and  9  cm.  diameter,  having  a  small 
hole  for  observing  the  flame. 

(/)  Cylinders. — The  cylinders  used  in  collecting  the  distillate 
shall  have  a  capacity  of  25  cc.,  and  shall  be  graduated  to  0.1  cc. 

(4)  SETTING    UP    APPARATUS. — Connect    the    distilling   flask 
containing  the  tar  to  the  air  condenser  with  a  one-hole  stopper. 
Insert  the  thermometer  through  a  one-hole  stopper  in  the  top  of 
the  flask  in  such  a  way  that  the  top  of  the  bulb  is  opposite  the 
middle  of  the  side  arm  opening  of  the  flask.     Have  the  burner  so 
adjusted  that  the  shield  will  completely  protect  the  flame  and  also 
the  bulb  of  the  distilling  flask. 

(5)  PROCEDURE. — Weigh  exactly  100  cc.  of  the  dehydrated 
material   into   the   distilling   flask,    which   has   been   previously 
weighed.     Adjust     the     thermometer,     shield,     condenser,     etc. 
Commence  distillation,  so  regulating  the  rate  that  1  cc.  passes 
over  every  minute.     Change  the  receiver  as  the  mercury  column 
just  passes  the  fractionation  point. 

Report  the  temperature  at  which  the  first  drop  comes  over 
and  then  report  the  per  cent  of  each  of  the  following  fractions,  both 
by  weight  and  by  volume : 

,Up  to  110°C. 
110-170° C. 
170-235°  C. 
235-270°  C. 
270-315°  C. 
315-355°  C. 
Residue  above  355°  C. 

*0r  Tirrill. 


554  TECHNICAL  METHODS  OF  ANALYSIS 

The  residue  is  determined  by  cooling  the  flask  after  distillation 
and  weighing  it.  During  the  distillation  the  condenser  tube  should 
be  warmed  when  necessary  to  prevent  deposition  of  any  sublimate. 

NOTE. — This  method  is  based  on  standard  method  D20-18  of  the  Amer- 
can  Society  for  Testing  Materials,  1918. 

Tar  Acids. — Distill  a  known  volume  of  the  tar  up  to  315°  C. 
For  each  100  cc.  of  distillate  add  40  cc.  of  an  approximately  20% 
solution  of  NaOH.  Warm  slightly  while  stirring  and  place  in  a 
separatory  funnel.  Shake  vigorously  and  let  stand  until  the  oil  and 
soda  solutions  separate,  and  draw  off  the  latter  containing  most 
of  the  tar  acids.  Make  a  second  and  third  extraction,  using  75% 
and  50%  of  the  original  volume  of  NaOH  solution,  respectively. 
Unite  the  three  alkaline  extracts  in  a  200  cc.  graduated  cylinder 
(see  below)  and  acidify  with  dil.  H2S(>4.  Let  cool  and  read  the 
volume  of  tar  acids.  From  the  amount  of  tar  taken  calculate  the 
per  cent  by  volume  of  tar  acids  in  the  original  tar. 

NOTE. — The  cylinder  or  separatory  funnel  should  be  of  special  form  with  a 
stopcock  and  graduated  stem  so  that  the  tar  acids  may  be  drawn  down  in  the 
graduated  portion  and  the  volume  accurately  determined. 

Sulfur. — See  page  191. 

Road  Tars. — The  examination  of  road  tars  is  usually  made  to 
conform  to  special  specifications  which  describe  the  method.  If 
methods  are  not  specified,  follow  the  procedures  on  page  537. 

REFERENCES. — Gas  Chemists'  Handbook,  1916.  Am.  Soc.  for  Testing 
Materials:  Standards,  1918,  page  669. 

SPENT  OXIDE 

General. — The  material  used  for  the  removal  of  H2S  from 
illuminating  gas  is  known  under  various  names,  such  as  oxide, 
iron  oxide,  iron  mass,  iron  sponge,  etc.  After  it  has  been  in  use 
for  some  time,  it  is  generally  referred  to  as  "  spent  oxide."  It 
consists  of  wood  shavings  mixed  with  hydrated  ferric  oxide.  The 
action  of  H2S  on  this  material  is  probably  represented  by  the 
following  equations: 

Fe203  •  H2O+3H2S  =  Fe2S3+4H2O, 
and  Fe2O3  •  H2O+3H2S  =  2FeS+S+4H2O. 


MISCELLANEOUS  ANALYSES  555 

After  the  material  has  become  "  foul/'  it  is  revivified  or  reox- 
idized  by  exposure  to  air.  The  reactions  here  are  probably  as 
follows : 

2Fe2S3+3O2  =  2Fe2O3+6S, 

and  4FeS+3O2  =  2Fe203+4S. 

There  are  also  present  Prussian  blue  and  other  cyanogen  and 
carbonyl  products.  In  selling  the  material  for  its  cyanogen  con- 
tent, it  is  customary  to  calculate  the  latter  in  terms  of  crystallized 
potassium  ferrocyanide,  K4Fe(CN)6-3H20. 

Moisture. — When  the  material  arrives  in  the  laboratory,  it  is 
usually  in  such  condition,  due  to  moisture  and  tarry  matter,  that 
it  must  be  dried  before  grinding.  Mix  the  sample  thoroughly 
and  weigh  out  100  grams  (or  more  if  possible)  into  a  rectangular 
tin  dish  and  dry  to  constant  weight,  keeping  the  temperature  as 
nearly  as  possible  between  90  and  95°  C.  When  ferrocyanide  is  to 
be  determined,  dry  for  nine  hours  at  50-60°  C.  It  is  unsafe  to 
hasten  drying  by  raising  the  heat,  as  this  will  volatilize  some  of 
the  free  sulfur,  and  may  decompose  Prussian  blue. 

Preparation  of  Sample. — Grind  the  dried  sample  in  an  ordinary 
coffee  mill,  repeating  the  grinding  until  the  material  is  as  fine  as 
possible.  By  bringing  the  grinding  surfaces  closer  together  each 
time,  it  is  possible  to  reduce  the  mass  almost  to  a  powder.  For 
accurate  work,  determine  the  residual  moisture  in  the  ground 
sample  and  make  such  corrections  as  are  necessary  in  figures 
obtained  in  the  subsequent  analysis  to  bring  them  to  the  basis 
of  the  original  material. 

NOTE. — In  grinding  it  is  very  essential,  in  case  ferrocyanide  is  to  be  deter- 
mined, that  the  temperature  should  not  get  above  50-60°  C.,  as  excessive  heat- 
ing will  cause  loss  of  cyanogen. 

Free  Sulfur. — Since,  for  commercial  purposes,  S  combined  as 
iron  sulfide  may  be  considered  in  the  same  category  as  free  S, 
the  analysis  is  shortened  by  determining  these  two  forms  of  S 
together.  The  method  is  based  on  the  fact  that  free  S  is  dis- 
solved by  CS2.  Since  the  latter,  however,  will  dissolve  only  free 
S,  some  of  the  sample  should  be  spread  out  and  exposed  to  air 
for  "  revivification  "  before  extracting.  The  sample  must  also 
be  dry,  since  moisture  interferes  with  the  extraction. 


556  TECHNICAL  METHODS  OF  ANALYSIS 

Weigh  5  grams  of  the  ground  dry  material  on  a  watch  glass  and 
heat  in  a  water  oven  at  not  over  95°  C.  to  constant  weight  in  order 
to  remove  the  last  traces  of  moisture.  Transfer  to  a  Soxhlet 
thimble  and  extract  with  recently  distilled  c.  P.  082  *  until  no 
further  material  is  extracted,  collecting  the  extract  in  a  weighed 
flask.  Distill  off  the  082  on  the  water  bath  through  a  Liebig 
condenser.  Dry  the  residue  to  constant  weight  at  not  over  100°  C. 
The  weight  gives  the  amount  of  tar  and  free  S. 

Add  to  the  flask  50  cc.  of  fuming  HNOa,  evaporate  on  the  hot 
plate  or  sand  bath  to  half  its  volume,  then  add,  little  by  little,  3 
grams  of  KClOs,  and  evaporate  to  dryness.  Bake  on  the  hot 
plate  for  one-half  hour,  cool  and  add  30  cc.  of  HC1  (1  :  1).  JBoil, 
filter  and  wash  with  hot  water.  Heat  the  filtrate  to  boiling  and 
add  slowly  a  boiling  10%  solution  of  BaCk  in  excess.  Boil  for 
one-half  hour,  or  let  stand  overnight;  filter  hot,  and  ignite  and 
weigh  the  BaSC^  in  the  usual  way.  Calculate  the  weight  to 
sulfur. 

CALCULATION.— BaSO4  X  0.1373  -  S. 

NOTES. — (1)  The  CS2  extraction  is  a  slow  one;  the  length  of  time  required 
depends  upon  the  percentage  of  S  and  the  amount  of  tar.  Usually  thirty 
hours  will  be  sufficient. 

(2)  The  free  S  in  spent  oxides  may  run  from  a  few  per  cent  to  as  high  as 
55  or  60%. 

Tar. — The  weight  of  S  subtracted  from  the  total  weight  of 
C$2  extract  gives  the  weight  of  tar. 

Combined  Sulfur. — If  it  is  desired  to  determine  the  combined  S, 
this  may  be  done  on  the  residue  from  the  C$2  extraction,  after 
making  sure  that  all  C$2  has  been  expelled.  After  oxidizing  with 
fuming  HNOs,  as  described  under  Free  Sulfur,  and  filtering,  dry 
the  undecomposed  material  on  the  filter  paper  and  fuse  it  with 
equal  parts  of  Na2COs  and  NaNOs.  Disintegrate  with  hot  water, 
filter  and  wash.  Dilute  the  filtrate  to  250  cc.  and  acidulate  with 
HC1.  Boil  off  CO2  and  precipitate  hot  with  excess  of  BaCl2 
solution.  Add  the  S  thus  found  to  the  S  found  by  the  HNOs 
treatment.  The  sum  gives  combined  S. 

*  CS2  is  very  inflammable  and  in  the  gaseous  state,  when  mixed  with  a 
certain  percentage  of  air,  is  highly  explosive.  The  extraction  apparatus  should 
never  be  disconnected  until  it  has  cooled  down  to  room  temperature. 


MISCELLANEOUS  ANALYSES  557 

Potassium  Ferrocyanide  (Modified  Knublauch  Method). — 
MOISTURE. — Dry  30  grams  of  the  material  for  nine  hours  at 
50-60°  C. 

EXTRACTION  OF  PRUSSIAN  BLUE. — Grind  the  dried  oxide 
until  it  all  passes  an  80-mesh  sieve,  taking  care  to  avoid  heating. 
Introduce  10  grams  of  this  fine  material  into  a  250  cc.  volumetric 
flask.  Add  50  cc.  of  10%  KOH  solution  and  .let  stand  15-16  hours 
at  room  temperature,  shaking  frequently.  Then  make  up  to 
250  cc.  and  add  5  cc.  more  to  compensate  for  the  volume  of  the 
oxide.  Shake  vigorously  and  filter  through  a  dry  filter.  Some 
free  S  may  come  through  the  filter  paper,  but  most  of  this  can 
be  removed  by  refiltering  through  the  same  paper.  What  remains 
will  do  no  harm. 

Pipette  out  100  cc.  of  this  filtrate  and  let  it  run  slowly  into  50  cc. 
of  a  boiling  solution  of  FeCla.*  Boil  the  mixture  a  few  minutes  to 
complete  the  precipitation  of  the  Prussian  blue.  After  this 
settles  a  little,  filter  and  wash  with  boiling  water  until  the  wash- 
ings are  free  from  acid. 

Transfer  the  blue,  together  with  the  filter  paper,  into  a  400  cc. 
beaker  and  add  25  cc.  of  10%  KOH  solution.  After  complete 
decomposition,  transfer  to  a  250  cc.  volumetric  flask  and  make  up 
to  the  mark.  Shake  and  filter  through  a  dry  filter.  Use  100  cc.  of 
this  filtrate  for  titration. 

'  PREPARATION  OF  SOLUTIONS. — (1)  Zinc  Sulfate  Solution. — 
Weigh  out  10  grams  of  c.  P.  ZnSC^-TEbO,  dissolve  in  water,  add 
10  cc.  of  cone.  H2S04  and  dilute  to  1  liter. 

(2)  Potassium  Ferrocyanide  Solution. — Weigh  out  exactly  5 
grams  of  K4Fe(CN)6-3H20.  This  should  be  chemically  pure  and 
contain  the  full  amount  of  water  of  crystallization.  If  the  latter 
is  more  or  less,  a  correction  must  be  made.  Dissolve  in  water 
and  make  up  to  250  cc. 

STANDARDIZATION  OF  ZNSO*  SOLUTION. — Measure  out  25  cc.  of 
the  ferrocyanide  solution  into  a  beaker.  Add  about  50  cc.  of 
water  and  10  cc.  of  10%  H2SO4.  Titrate  with  the  ZnSO4  solution 
from  a  burette. 

As  an  outside  indicator  use  a  3%  solution  of  ferric  alum  on 

*  Dissolve  60  grams  of  FeCl3  crystals  in  water,  add  100  cc.  of  cone.  HC1 
and  dilute  to  1  liter. 


558  TECHNICAL  METHODS  OF  ANALYSIS 

Schleicher  and  Schull's  drop  reaction  paper  No.  601.*  Place  1 
drop  of  ferric  alum  solution  on  the  paper  and  let  it  spread  as  far 
as  it  will.  Place  a  drop  of  the  solution  being  titrated  so  that  its 
extreme  edge,  after  spreading,  just  meets  the  edge  of  the  ferric 
alum  drop.  If  the  two  over-run,  faulty  results  will  follow.  The 
end-point  of  the  titration  is  reached  when  a  blue  coloration  at  the 
point  where  the  2  drops  meet  does  not  appear  for  a  space  of  one 
minute.  Questionable  end-points  may  be  detected  by  holding  the 
test  paper  so  that  strong  sunlight  passes  through  it.  The  faintest 
trace  of  blue  is  readily  detected  in  this  way.  Titrations  should 
not  be  attempted  by  artificial  light  or  on  dull  cloudy  days.  At 
least  three  titrations  should  be  made,  the  first  to  find  the  approxi- 
mate amount  of  ZnSO4  solution  required.  The  second  and  third 
titrations  should  check  each  other  closely. 

From  the  titration  calculate  the  value  of  1  cc.  of  ZnSO4  solu- 
tion in  terms  of  K4Fe(CN)6-3H2O. 

TITRATION  OF  PREPARED  SOLUTION. — Place  in  a  beaker  100  cc. 
of  the  solution  prepared  as  described  under  Extraction  of  Prussian 
Blue.  Add  a  drop  or  two  of  methyl  orange  indicator,  neutralize 
with  10%  H2SO4  and  then  add  10  cc.  excess.  Titrate  with  stand- 
ard ZnSO4  solution,  using  ferric  alum  as  outside  indicator,  exactly 
as  in  the  standardization.  From  the  strength  of  the  ZnSO4 
solution  calculate  the  per  cent  of  K4Fe(CN)6-3H2O  both  in  the 
sample  as  received  and  on  the  dry  basis. 

NOTE. — The  entire  success  of  the  method  depends  upon  obtaining  the 
correct  end-point.  Titrations  must  be  carried  out  in  strong  sunlight,  never 
by  artificial  light. 

REFERENCES. — Proceedings  of  American  Gas  Institute,  7,  761;  R.  H. 
Royle:  "  Chemistry  of  Gas  Manufacture,"  page  174;  "  Gas  Chemists' 
Handbook.  " 

• 

*  This  is  the  only  paper  which  we  have  found  satisfactory.  Other  papers, 
such  as  Whatman's,  give  a  blue  color  directly  with  the  reagent.  They  can  be 
made  satisfactory,  however,  by  treatment  with  very  dil.  HC1  as  follows: 
Place  the  entire  sheet  in  a  large  beaker  and  cover  it  with  HC1  of  between  2 
and  5%  strength.  Boil  gently  or  digest  on  the  steam  bath  for  about  one- 
half  hour.  Wash  free  from  acid;  then  continue  washing  until  free  from  chlo- 
rine. Dry  in  the  air  protected  from  chemical  fumes. 


MISCELLANEOUS  ANALYSES  559 


MORTAR  AND  CONCRETE 

General. — Structural  concrete  consists  of  sand,  gravel  and 
cement.  In  mortar  the  gravel  (large  aggregate)  is  omitted. 
In  some  mortars  also  lime  is  used.  These  lime  mortars  generally 
contain  an  amount  of  lime  about  equal  to  the  amount  of  cement. 
The  setting  of  cement  is  a  process  of  hydration;  therefore,  in 
order  to  obtain  the  composition  of  the  original  material,  the 
analysis  must  be  made  on  the  sample  after  ignition.. 

Gravel. — Any  stone  or  coarse  aggregate  which  will  not  pass 
through  a  sieve  with  J-inch  openings  *  is  considered  gravel; 
material  finer  than  J-inch  is  considered  sand.  If  the  composition 
contains  gravel,  the  whole  sample  should  be  weighed  and  disin- 
tegrated with  a  hammer  or  mortar  and  pestle,  taking  care  not  to 
crush  or  break  the  stone  or  sand  particles.  Knock  off  the  cement 
from  the  large  particles.  Then  determine  the  percentage  of  the 
whole  sample  which  will  not  go  through  a  J-inch  sieve  and  report 
as  "  gravel." 

Thoroughly  mix  the  finer  portion,  and  weigh  out  a  known 
quantity,  generally  10-50  grams,  depending  upon  the  size  of  the 
particles.  Ignite  and  determine  loss  on  ignition.  Then  proceed 
with  the  determinations  of  Sand,  etc.,  as  below,  beginning  "  Treat 
with  a  considerable  volume  of  dil.  HC1." 

Sand. — If  the  original  material  is  fine  and  appears  to  be  fairly 
uniform  (as  in  the  case  of  mortars  and  surfacings),  crush  gently 
and  mix  thoroughly.  Ignite  a  portion  and  weigh  out  5-10  grams 
of  the  ignited  sample.  Treat  with  a  considerable  volume  of  dil. 
HC1  (not  stronger  than  1  part  cone,  acid  to  10  parts  water)  and 
warm  on  the  steam  bath.  Decant  the  liquid  through  a  filter  into 
a  graduated  flask.  (If  CaO  and  MgO  are  not  to  be  determined, 
discard  the  filtrate;  see  Note  2.)  Add  a  second  portion  of  dil. 
HC1,  again  warm  and  decant.  Continue  this  until  all  soluble 
matter  has  been  removed.  Wash  with  hot  water,  finally  trans- 
ferring all  the  residue  to  the  filter.  Ignite  in  a  weighed  crucible, 
cool  in  a  desiccator  and  weigh.  This  gives  the  sand. 

NOTES. — (1)  Some  of  the  SiO2  from  the  cement  may  be  thrown  out  of 
solution  as  silicic  acid.     The  amount,  however,  is  small  if  dilute  acid  is  used 

*  This  is  not  a  4-mesh  sieve,  i.e.,  a  sieve  with  four  openings  to  the  inch. 


560  TECHNICAL  METHODS  OF  ANALYSIS 

and  is  largely  compensated  by  the  small  amount  of  iron  and  alumina  which  is 
dissolved  from  the  sand. 

(2)  In  case  of  concrete  and  mortars  free  from  added  lime  or  limestone, 
it  is  sufficiently  accurate  to  consider  the  rest  of  the  material  as  cement.  From 
the  loss  on  ignition  of  the  sand  plus  cement  calculate  what  the  weight  of 
the  entire  sample  would  have  been  after  ignition  and  on  this  weight  figure  the 
percentages  of  gravel  and  sand,  and  take  cement  "  by  difference." 

Total  Lime  and  Magnesia. — If  the  material  contains  added 
lime  or  limestone,  make  the  filtrate  up  to  volume  and  take  an 
aliquot  representing  about  2  grams  of  the  original  ignited  portion. 
Make  slightly  alkaline  with  NH^OH,  boil,  and  filter  out  any  Fe 
and  Al  hydroxides.  To  the  hot  filtrate  add  an  excess  of 
(NH4) 20264  solution.  Heat  to  boiling  and  let  stand  until  the 
precipitate  settles  clear.  Filter,  wash  with  hot  water  and  ignite 
over  a  blast  lamp.  Cool  in  a  desiccator  and  weigh  as  CaO. 
(The  CaC204  may  also  be  titrated  with  0.1  N  KMnO4  in  the  usual 
way  instead  of  igniting.) 

Test  a  little  of  the  filtrate  from  the  CaO  determination  for  MgO. 
If  any  appreciable  amount  is  present  it  must  be  determined  as 
follows:  Return  the  port 'on  of  the  filtrate  on  which  the  qualitative 
test  was  made  to  the  main  filtrate.  Make  slightly  acid  with  HC1 
and  evaporate  until  crystallization  begins.  Cool  and  dilute  suf- 
ficiently to  redissolve  any  crystals.  Add  a  considerable  excess  of  a 
solution  of  Na  or  NH4  phosphate  and  then  make  strongly  ammo- 
niacal.  Let  stand  overnight  (or  cool  in  ice  water  and  stir  for 
about  one-half  hour).  Filter  through  a  weighed  Gooch  crucible, 
wash  with  a  mixture  of  1  part  of  NH40H  (1  :  1),  1  part  of  alcohol, 
and  3  parts  of  water.  Ignite  very  gently  at  first  and  finally  blast 
thoroughly.  Cool  in  a  desiccator  and  weigh  as  Mg2?2O7.  Cal- 
culate to  MgO. 

CALCULATION.— Mg2P2O7X  0.3621  =  MgO. 

NOTE. — Since  the  entire  procedure  gives  of  necessity  only  approximate 
results,  it  is  not  necessary  to  make  a  double  precipitation  of  the  CaC2O4 
before  determining  Mg. 

CALCULATIONS. — If  the  brand  of  cement  is  known,  look  up  the 
amount  of  CaO  it  contains.  If  the  brand  is  not  known,  assume 
that  it  contains  62%  CaO.  Then,  assuming  that  the  ignited 
material  consists  entirely  of  sand,  cement,  and  free  lime  (and  MgO), 


MISCELLANEOUS  ANALYSES  561 

and  that  the  cement  itself  contains  62%  CaO  (+MgO),  calculate 
the  proportions  in  the  sample  as  follows: 

Subtract  the  per  cent  of  sand  and  gravel  from  100%.     The 
difference  is  cement  +  CaO  +  MgO.     (This  is  B  below.) 

Let     A  =  Total  CaO+MgO  (found  by  analysis)  ; 

B  =  Cement  +  free  CaO+free  MgO; 
and          X  =  Cement  ; 
then  B-X  =  Free  (CaO+MgO), 
and          A  =  5-^+0.62  X 

=  B-0.38X. 
Or    0.38X  =  B-A; 


NOTE.  —  If  high-grade  lime  was  used,  there  will  be  very  little  MgO  present; 
but  if  dolomitic  lime  was  used,  there  will  be  considerable  MgO.  * 


SAMPLING  AND  PHYSICAL  TESTING  OF  PORTLAND  CEMENT 

General. — The  following  procedure  is  based  on  specification 
C  9-17  of  the  American  Society  for  Testing  Materials.  Portland 
cement  is  there  defined  as  "  the  product  obtained  by  finely  pulver- 
izing clinker  produced  by  calcining  to  incipient  fusion  an  intimate 
and  properly  proportioned  mixture  of  argillaceous  and  calcareous 
materials,  with  no  additions  subsequent  to  calcination  excepting 
water  and  calcined  or  uncalcined  gypsum." 

Portland  cement  is  usually  purchased  on  the  basis  of  physical 
tests  only,  and  unless  expressly  requested,  no  chemical  tests  are 
necessary. 

Specification  for  Physical  Requirements. — The  standard  speci- 
fications of  the  A.  S.  T.  M.  were  revised  in  1916  to  become  effective 
January  1,  1917.  Unless  otherwise  instructed,  cement  is  to  be 
tested  according  to  the  revised  specifications.  As  some  engineers, 
however,  request  tests  according  to  the  old  specifications,  both 
requirements  are  given  below: 


562 


TECHNICAL  METHODS  OF  ANALYSIS 


Old  Specifications 

New  Specifications 

Maximum 

Minimum 

Maximum 

Minimum 

Specific  Gravity: 
Ordinary  Portland  cement. 
White  Portland  cement.  .  . 

Fineness,  per  cent: 
Residue  on  100-mesh  sieve.  . 
Residue  on  200-mesh  sieve  . 

Initial  set: 
Gillmore  needle    . 



3.10 

3.10 
3.07 

8%" 
25% 

22% 

60  minutes 
45  minutes 

Vicat  needle  

Final  set: 
Gillmore  needle  . 

30  minutes 

10  hours 
10  hours 

Vicat  needle  

10  hours 

1  hour 

175  Ibs. 
500  Ibs. 
600  Ibs. 

200  Ibs. 
275  Ibs. 

Tensile  strength  (neat) 
24  hours  
7  days 

28  days  

Tensile  strength  (1:3  mortar) 
7  days                     



200  Ibs. 
300  Ibs. 

28  days  

A  pat  of  neat  cement  shall  remain  firm  and  hard  and  show  no 
signs  of  distortion,  cracking,  checking,  or  disintegration  in  the 
steam  test  for  Soundness  described  below. 

A  bag  of  cement  shall  contain  94  Ibs.  net;  a  barrel,  376  Ibs.  net. 

NOTES. — (1)  If  the  sample  under  test  falls  below  the  sp.  gr.  requirement, 
a  second  test  may  be  made  on  an  ignited  sample.  The  sp.gr.  test  is  not 
required  by  the  revised  specifications  and  will  not  be  made  unless  requested. 

(2)  The  average  tensile  strength  of  standard  mortar  at  twenty-eight  days 
shall  always  be  higher  than  the  strength  at  seven  days. 

(3)  At  least  ten  days  from  the  time  of  sampling  shall  be  allowed  for  the 
completion  of  the  seven-day  test  and  thirty-one  days  for  the  twenty-eight-day 
test. 

(4)  The  Gillmore  needle  is  used  on  setting  tests  in  this  laboratory  unless 
otherwise  requested. 


MISCELLANEOUS  ANALYSES  .  563 

Rejection. — Cement  may  be  rejected  if  it  fails  to  meet  any  of 
the  requirements  of  the  specifications.  It  shall  not  be  rejected 
on  account  of  failure  to  meet  the  fineness  requirement  if,  upon 
retest  after  drying  at  100°  C.  for  one  hour,  it  meets  this  require- 
ment. Cement  failing  to  meet  the  soundness  test  in  steam  may  be 
accepted  if  it  passes  a  retest,  using  a  new  sample,  at  any  time 
within  twenty-eight  days  thereafter. 

Packages  varying  more  than  5%  from  the  specified  weight 
may  be  rejected;  and  if  the  average  weight  of  50  packages  taken 
at  random  from  any  shipment  is  less  than  that  specified,  the  entire 
shipment  may  be  rejected. 

Sampling. — Tests  may  be  made  on  individual  or  composite 
samples.  Each  test  sample  should  weigh  at  least  8  Ibs.  Samples 
should  preferably  be  shipped  and  stored  in  air-tight  con- 
tainers. 

(a)  INDIVIDUAL  SAMPLE — If  sampled  in  cars,  take  one  test 
sample  from  each  50  bbls.  or  fraction  thereof.  If  sampled  in 
bins,  take  1  sample  from  each  100  bbls. 

(6)  COMPOSITE  SAMPLE. — If  sampled  in  cars,  take  one  sampler- 
ful  from  1  of  each  40  sacks  (or  from  1  of  each  10  bbls.)  and  com- 
bine them  to  form  1  test  sample.  If  sampled  in  bins  or  ware- 
houses, take  1  test  sample  for  each  200  bbls.  or  fraction 
thereof. 

(c)  SAMPLING  AT  MILL. — Use  any  of  the  following  methods 
that  may  be  practicable,  as  ordered : 

(1)  From  the  conveyor  delivering  to  the  bin. — Take  at  least 
8  Ibs.  of  cement  from  approximately  each  100  bbls.  passing  over 
the  conveyor. 

(2)  From  filled  bins  by  means  of  proper  sampling  tubes. — Tubes 
inserted  vertically  may  be  used  for  sampling  cement  to  a  maximum 
depth  of  10  feet.     Tubes  inserted  horizontally  may  be  used  where 
the  construction  of  the  bin  permits.     Samples  shall  be  taken 
from  points  well  distributed  over  the  face  of  the  bin. 

(3)  From  filled  bins  at  points  of  discharge. — Sufficient  cement 
shall  be  taken  from  the  discharge  openings  to  obtain  samples 
representative  of  the  cement  contained  in  the  bin,  as  determined 
by  the  appearance  at  the  discharge  openings  of  indicators  placed 
on  the  surface  of  the  cement  directly  above  these  openings  before 
drawing  of  the  cement  is  started. 


564  TECHNICAL  METHODS  OF  ANALYSIS 

Preparation  of  Sample. — Pass  the  sample  through  a  sieve  hav- 
ing 20  meshes  per  linear  inch  in  order  to  thoroughly  mix  the 
sample,  break  up  lumps  and  remove  foreign  material. 

Specific  Gravity. — Determine  the  sp.  gr.  with  the  Le  Chatelier 
apparatus,  standardized  by  the  Bureau  of  Standards.  Use  kero- 
sene, free  from  water,  or  benzine  not  lighter  than  62°  Baume. 
Fill  the  flask  with  either  of  these  liquids  to  a  point  on  the  stem 
between  0  and  1  cc.  and  introduce  slowly  64  grams  of  cement 
of  the  same  temperature  as  the  liquid,  taking  care  that  the  cement 
does  not  adhere  to  the  inside  of  the  flask  above  the  liquid  and  to 
free  the  cement  from  air  by  rolling  the  flask  in  an  inclined  position. 
After  all  the  cement  is  introduced,  the  level  of  the  liquid  will  rise 
to  some  division  of  the  graduated  neck.  The  difference  between 
readings  is  the  volume  displaced  by  64  grams  of  the  cement.  Cal- 
culate the  sp.  gr.  from  the  formula: 

g       r  ==_ 64_ 

displaced  volume  (cc.)' 

Keep  the  flask  immersed  in  water  during  the  operation  to 
avoid  variations  in  the  temperature  of  the  liquid  in  the  flask 
(which  should  not  exceed  0.5°  C.)  and  report  results  to  2  decimal 
places.  Check  determinations  should  agree  within  0.01. 

NOTE. — The  sp.  gr.  is  to  be  determined  on  the  cement  as  received;  if  it 
falls  below  3.10  (or  3.07  for  white  cement),  make  a  second  determination 
after  igniting  the  sample  in  a  muffle  at  a  temperature  between  900  and  1000°  C. 
Ignite  at  this  temperature  for  fifteen  minutes  and  then  for  periods  of  five 
minutes  to  constant  weight. 

Fineness. — Place  50  grams  of  cement  on  a  clean,  dry  200-mesh 
sieve  with  pan  and  cover  attached,  if  desired,  and  hold  in  one  hand 
in  a  slightly  inclined  position  so  that  the  sample  will  be  well 
distributed  over  the  sieve,  at  the  same  time  gently  striking  the 
side  about  150  times  per  minute  against  the  palm  of  the  other  hand 
on  the  upstroke.  Turn  the  sieve  every  25  strokes  about  one-sixth 
of  a  revolution  in  the  same  direction.  Continue  the  operation 
until  not  more  than  0.05  gram  passes  through  in  one  minute  of 
continuous  sieving.  Weigh  the  residue  on  the  sieve  in  grams  and 
multiply  by  2  to  obtain  the  per  cent  of  residue. 

NOTES. — (1)  A  permissible  variation  of  1%  will  be  allowed  and  all  results 
between  22.0  and  23.0%  shall  be  reported  as  22.0%. 


MISCELLANEOUS  ANALYSES  565 

(2)  Routine  sieving  is  done  in  this  laboratory  on  a  Ro-tap  mechanical  sifter. 
The  sifter  is  run  for  fifteen  minutes,  the  fine  material  in  the  pan  discarded  and 
then  the  sieving  continued  for  five-minute  periods  until  no  more  material 
comes  through  the  sieve.     In  case,  however,  any  sample  fails  to  pass  on  the 
Ro-tap  tester,  it  shall  not  be  rejected  until  checked  by  the  hand  method  above 
described. 

(3)  The  200-mesh  sieve  used  must  be  standardized  by  the  U.  S.  Bureau  of 
Standards.     It  should  have  200  wires  per  inch  and  the  number  of  wires  in  any 
whole  inch  should  not  be  less  than  192  nor  more  than  208.     No  opening  be- 
tween adjacent  parallel  wires  should  be  more  than  0.0050  inch.     The  diameter 
of  the  wire  should  be  0.0021  inch  and  the  average  diameter  should  not  be  less 
than  0.0019  nor  more  than  0.0023  inch.     The  value  of  the  sieve  as  determined 
by  sieving  tests  made  in  conformity  with  the  standard  specification  for  these 
tests  on  a  standardized  cement  which  gives  a  residue  of  25-20%  on  the 
200-mesh  sieve,  or  on  other  similarly  graded   material,  should   not  show  a 
variation  of  more  than    1.5%  above  or  below  the  standards  maintained  at 
the  Bureau  of  Standards. 

(4)  The  old  specifications  required  a  100-mesh  sieve  test.     This  test  is 
made  in  the  same  way  as  the  200-mesh  test,  using  a  100-mesh  sieve  of  the 
following  specifications : 

Diameter  of  wire,  inch 0. 0042-0 . 0048 

Meshes  per  linear  inch 

Warp 95-101 

Woof 93-103 

Preparation  of  Neat  Paste  or  Mortars. — The  quantity  of  dry 
material  to  be  mixed  at  one  time  must  be  between  500  and  1000 
grams.  Weigh  out  the  dry  materials  to  the  nearest  gram,  place 
on  a  non-absorbent  surface  (glass  is  satisfactory),  thoroughly  mix 
dry,  if  sand  is  used,  and  form  a  crater  in  the  center,  into  which 
pour  the  proper  percentage  of  clean  water.  Turn  the  material 
on  the  outer  edge  into  the  crater  by  means  of  a  trowel.  After 
an  interval  of  one-half  minute  for  the  absorption  of  the 
water,  complete  the  operation  by  continuous,  vigorous  mixing, 
squeezing  and  kneading  with  the  hands  for  at  least  one  minute. 
Protect  the  hands  by  rubber  gloves  during  the  mixing. 

NOTES. — (1)  The  temperature  of  the  room  and  the  mixing  water  should  be 
maintained  as  nearly  as  practicable  at  21°  C.  (70°  F.). 

(2)  In  order  to  secure  Uniformity  in  the  results  of  tests  for  the  time  of 
setting  and  tensile  strength,  the  manner  of  mixing  as  above  described  should 
be  carefully  followed.  At  least  one  minute  is  necessary  to  obtain  the  desired 
plasticity,  which  is  not  appreciably  affected  by  continuing  the  mixing  for 
several  minutes.  The  exact  time  necessary  depends  upon  the  personal  equa- 
tion of  the  operator.  Any  error  in  mixing  should  be  on  the  side  of  over-mixing. 


566 


TECHNICAL  METHODS  OF  ANALYSIS 


Normal  Consistency. — Use  the  standard  Vicat  apparatus  (Fig. 
27),  which  consists  of  a  frame  bearing  a  movable  rod  weighing  300 
grams,  one  end  being  1  cm.  in  diameter  for  a  distance  of  6  cm.  and 
the  other  having  a  removable  needle  1  mm.  in  diameter,  6  cm-, 
long.  The  rod  is  reversible  and  may  be  held  in  any  desired  posi- 
tion by  a  screw,  and  has  midway  between  the  ends  a  milli- 
meter scale  attached  to  the  frame.  The  paste  is  held  in  a  conical, 
hard-rubber  ring,  7  cm.  in  diameter  at  the  base,  4  cm.  high,  resting 
on  a  glass  plate  about  10  cm.  square. 


FIG.  27. — Vicat  Apparatus. 

In  making  the  determination,  weigh  out  500  grams  of  cement 
and  knead  into  a  paste  with  a  measured  quantity  of  water  as 
described  previously.  Quickly  form  into  a  ball  with  the  hands, 
completing  the  operation  by  tossing  it  six  times  from  one  hand 
to  the  other,  maintained  about  6  inches  apart. 

Press  the  ball,  resting  in  the  palm  of  one  hand,  into  the  larger 
end  of  the  rubber  ring  held  in  the  other  hand,  completely  filling 
the  ring  with  paste;  then  remove  the  excess  at  the  larger  end  by  a 
single  movement  of  the  palm  of  the  hand.  Place  the  ring  on  its 
larger  end  on  the  glass  plate  and  slice  off  the  excess  paste  at  the 


MISCELLANEOUS  ANALYSES 


567 


smaller  end  (top)  of  the  ring  by  a  single  oblique  stroke  of  a  trowel 
held  at  a  slight  an*gle  with  the  top  of  the  ring.  During  these 
operations  take  care  not  to  compress  the  paste. 

Place  the  paste  confined  in  the  ring,  resting  on  the  plate,  under 
the  rod  and  bring  the  larger  end  of  the  rod  in  contact  with  the  sur- 
face of  the  paste;  read  the  scale  and  quickly  release  the  rod.  The 
paste  is  considered  to  be  of  normal  consistency  when  the  rod  settles 
to  a  point  10  mm.  below  the  original  surface  in  one-half  minute 
after  being  released. 

The  apparatus  must  be  free  from  all  vibrations  during  the  test. 
Make  trial  pastes  with  varying  percentages  of  water  until  the 
normal  consistency  is  obtained.  Express  the  amount  of  water 
required  in  percentage  by  weight  of  the  dry  cement. 

Standard  Mortar  (1  :  3). — The  consistency  of  standard  mortar 
depends  upon  the  amount  of  water  required  to  produce  a  paste  of 
normal  consistency  from  the  same  sample  of  cement.  Having 
determined  the  normal  consistency  of  the  cement  sample,  the  con- 
sistency of  standard  mortar  made  from  the  same  sample  shall  be 
as  indicated  in  the  table  below,  the  values  being  given  in  per- 
centage of  the  dry  weights  of  the  cement  and  standard  sand. 
PERCENTAGE  OF  WATER  FOR  STANDARD  MORTARS 


Normal  Consistency 
Per  Cent  of  Water 
for  Neat  Cement 
Paste 

Per  Cent  of  Water 
for  1  :  3  Mortar 

Normal  Consist- 
ency Per  Cent  of 
Water  for  Neat 
Cement  Paste 

Per  Cent  of  Water 
for  1  :  3  Mortar 

15 
16 

9.0 
9.2 

23 
24 

10.3 
10.5 

17 

18 

9.3 
9.5 

25 
26 

10.7 
10.8 

19 
20 

9.7 

9.8 

27 
28 

11.0 
11.2 

21 
22 

10.0 
10.2 

29 
30 

11.3 
11.5 

Soundness. — Make  a  pat  of  cement  paste  of  normal  consistency 
about  3  inches  in  diameter,  0.5  inch  thick  at  the  center  and  taper- 


568  TECHNICAL  METHODS  OF  ANALYSIS 

ing  to  a  thin  edge,  on  a  clean  glass  plate  about  4  inches  square  and 
store  it  in  moist  air  for  twenty-four  hours.  'In  molding  the  pat, 
first  flatten  the  cement  paste  on  the  glass  and  then  form  the  pat 
by  drawing  the  trowel  from  the  outer  edge  toward  the  center. 

Then  place  the  pat  in  an  atmosphere  of  steam  at  a  temperature 
between  98  and  100°  C.  upon  a  suitable  support  .1  inch  above 
boiling  water  for  five  hours.  At  the  end  of  this  time,  examine 
the  pat  for  shrinkage,  absorption,  cracking,  checking  or  dis- 
integration. The  pat  should  be  firm  and  sound. 

NOTE. — Should  the  pat  leave  the  plate,  distortion  may  be  detected  best 
with  a  straight  edge  applied  to  the  surface  which  was  in  contact  with  the  plate. 

Time  of  Setting. — The  time  of  setting  may  be  determined 
either  with  the  Vicat  needle,  previously  described,  or  with  the 
Gillmore  needle.  Unless  otherwise  directed,  tests  in  this  labora- 
tory are  made  with  the  Gillmore  needles. 

(a)  With  Gillmore  needles. — Make  a  pat  of  neat  cement  about 
3  inches  in  diameter  and  0.5  inch  in  thickness  with  a  flat  top,  mixed 
to  normal  consistency,  and  keep  in  moist  air  at  a  temperature  main- 
tained as  nearly  as  practicable  at  21°  C.  Test  at  intervals  with  the 
standard  Gillmore  needles.  (Fig.  28.)  The  cement  shall  be  con- 
sidered as  having  acquired  its  initial  set  when  the  pat  will  bear, 
without  appreciable  indentation,  the  Gillmore  needle  TV  inch  in 
diameter,  weighing  0.25  Ib.  The  cement  has  acquired  its  final  set 
when  the  pat  will  bear  without  an  appreciable  indentation,  the 
Gillmore  needle  -£$  inch  in  diameter,  weighing  1  Ib.  In  making  the 
test  hold  the  needles  in  a  vertical  position  and  apply  lightly  to  the 
surface  of  the  pat. 

(6)  With  Vicat  needle. — Make  a  paste  of  neat  cement  of  normal 
consistency  and  mold  it  into  the  hard  rubber-ring  as  previously 
described  under  Normal  Consistency  above.  Place  it  under 
the  rod  and  then  carefully  bring  the  smaller  end  of  the  rod  in 
contact  with  the  surface  of  the  paste  and  quickly  release  the  rod. 
The  paste  has  reached  the  condition  of  initial  set  when  the  needle 
ceases  to  pass  a  point  5  mm.  above  the  glass  plate  in  one-half 
minute  after  being  released ;  and  final  set,  when  the  needle  does  not 
sink  visibly  into  the  paste. 

The  test  pieces  must  be  kept  in  moist  air  during  the  test.  The 
needle  must  be  kept  clean,  as  the  collection  of  cement  on  the  sides 


MISCELLANEOUS  ANALYSES 


569 


retards  the  penetration,  and  cement  on  the  point  may  increase  the 
penetration. 

NOTE. — Time  of  setting  is  affected  not  only  by  the  percentage  and  tem- 
perature of  the  water,  but  by  the  temperature  and  humidity  of  the  air,  and  its 
determination  is,  therefore,  only  approximate. 

Tensile  Strength. — The  tensile  strength  tests  are  made  on 
briquettes  having  a  cross  section  of  1  square  inch.  For  the  neat 
tests  use  a  neat  paste  made  up  to  normal  consistency.  For  mortar 


Rat  w'tb  Top  Surface  Flattened  for  Determining 
Time  of  Setting  by  Gillroore  Method. 


Q 


(Z>)  Gil  (more  Needles. 

FIG.  28. 

tests  make  a  standard  mortar  according  to  the  table  previously 
given  under  Normal  Consistency,  using  1  part  of  cement  to  3 
parts  of  standard  Ottawa  sand,  by  weight.  Use  standard  briquette 
molds  as  specified  by  the  A.  S.  T.  M.  Make  4  briquettes  for 
each  28-day  test  and  3  for  each  of  the  other  tests  called  for. 

Immediately  after  mixing,  place  the  paste  or  mortar  in  the 
molds  (wipe  the  molds  with  an  oily  cloth  before  using) ,  pressing  in 
firmly  with  the  thumbs  and  smoothing  off  with  a  trowel  without 
ramming.  Then  heap  up  additional  mortar  (or  paste)  above 


570 


TECHNICAL  METHODS  OF  ANALYSIS 


the  mold  and  smooth  off  with  a  trowel.     Draw  the  trowel  over  the 
mold  in  such  a  manner  as  to  exert  a  moderate  pressure  on  the  ma- 


FIG.  29. — Fairbanks  Cement  Testing  Machine. 

DIRECTIONS  FOR  USE 

Hang  the  cup  F  on  the  end  of  the  beam  D,  as  shown  in  the  illustration. 
See  that  the  poise  R  is  at  the  zero  mark,  and  balance  the  beam  by  turning  the 
ball  L.  Fill  the  hopper  B  with  fine  shot  (of  which  a  bag  is  provided  with 
each  machine) .  Place  the  briquette  in  the  clamps  N  N.  Tighten  the  hand 
wheel  g  sufficiently  to  cause  the  graduated  beam  D  to  rise  to  the  stop  K. 
Only  enough  pressure  should  be  exerted  to  hold  the  beam  firmly  against  the 
stop;  not  enough  to  transmit  any  strain  to  the  specimen.  Open  the  auto- 
matic valve  J  to  allow  the  shot  to  run  into  the  cup  F.  At  the  point  where  the 
spout  joins  the  reservoir  there  is  a  small  valve,  by  which  the  flow  of  shot  may 
be  regulated.  Better  results  will  be  obtained  by  allowing  the  shot  to  run 
very  slowly  into  the  cup.  When  the  briquette  breaks,  the  beam  D  will  drop 
and  automatically  close  the  valve  J. 

terial.     Then  turn  the  mold  over  and  repeat  the  operation  of  heap- 
ing, thumbing  and  smoothing  off.     Make  the  tests  on  the  standard 


MISCELLANEOUS  ANALYSES  571 

testing  machine  (Fig.  29),  which  should  be  frequently  calibrated 
in  order .  to  determine  its  accuracy.  The  briquettes  should  be 
tested  as  soon  as  they  are  removed  from  the  water.  See  that  the 
bearing  surfaces  of  the  clips  and  briquettes  are  free  from  grains 
of  sand  or  dirt.  Carefully  center  the  briquettes  and  apply  the 
load  continuously  at  the  rate  of  600  Ibs.  per  minute.  In  reporting 
results  give  the  breaking  strength  of  each  briquette  and  the 
average  of  the  3  briquettes. 

NOTES. — (1)  The  fourth  briquette  on  the  28-day  test  is  made  up  only  for 
use  in  case  anything  goes  wrong  with  one  of  the  other  briquettes.  If  any 
of  the  first  three  28-day  briquettes  appears  to  be  faulty  or  gives  a  breaking 
strength  widely  at  variance  with  the  other  two,  then  use  the  fourth  briquette 
in  place  of  the  faulty  one.  Otherwise  do  not  break  the  fourth  briquette. 

(2)  Briquettes  which  are  manifestly  faulty  or  which  give  strengths  differing 
more  than  15%  from  the  average  value  of  all  test  pieces  made  from  the  same 
samples  and  broken  at  the  same  period,  will  not  be  considered  in  determining 
the  tensile  strength. 

(a)  Storage  of  test  briquettes. — The  moist  closet  may  consist 
of  a  soapstone,  slate  or  concrete  box,  or  a  wooden  box  lined  with 
metal.  If  a  wooden  box  is  used,  the  interior  should  be  covered 
with  felt  or  broad  wicking  kept  wet.  The  bottom  of  the  moist 
closet  should  be  covered  with  water.  The  interior  of  the  closet 
should  be  provided  with  non-absorbent  shelves  on  which  to 
place  the  test  pieces. 

Unless  otherwise  specified,  all  test  pieces,  immediately  after 
molding,  shall  be  placed  in  the  moist  closet  for  twenty  to  twenty- 
four  hours.  The  briquettes  should  be  kept  in  the  molds  on  glass 
plates  in  the  moist  closet  for  at  least  twenty  hours.  After  twenty- 
four  hours  in  moist  air  the  briquettes  should  be  immersed  in  clean 
water  in  storage  tanks  of  non-corroding  material.  The  air  and 
water  should  be  maintained  as  nearly  as  possible  at  a  temperature 
of  21°  C.  The  briquettes  for  the  various  tests  shall  be  stored  as 
follows : 

24-four-hour  test:    Twenty-four  hours  in  moist  air. 

7rday  test :  One  day  in  moist  air,  6  days  in  water. 

28-day  test :  One  day  in  moist  air,  27  days  in  water. 

(6)  Standard  Ottawa  Sand. — Standard  sand-  shall  be  natural 
sand  from  Ottawa,  Illinois  (obtained  from  the  Ottawa  Silica  Com- 
pany), and  screened  to  pass  a  No.  20  sieve,  but  not  a  No.  30  sieve. 
The  sand,  having  passed  the  No.  20  sieve,  shall  be  considered 


572  TECHNICAL  METHODS  OF  ANALYSIS 

standard  when  not  more  than  5  grams  pass  the  No.  30  sieve  after 
one  minute  of  continuous  sieving  of  a  500-gram  sample.  ' . 

REFERENCE. — American  Society  for  Testing  Materials,  Triennial  Stand- 
ards (1918),  page  503,  ff. 

CHEMICAL  ANALYSIS  OF  PORTLAND  CEMENT 

General. — Portland  cement,  according  to  Le  Chatelier,  con- 
sists of  a  mixture  of  dry  calcium  silicate  and  dry  calcium  aluminate. 
It  may  also  contain,  and  generally  does  contain,  small  amounts 
of  magnesia  and  of  calcium  sulfate.  The  average  analysis  of 
13  samples  of  different  American  Portland  Cements  *  is  as  follows: 

Per  cent 

Silica,  Si02 21.85 

Iron  oxide,  Fe203 2.62 

Alumina,  A^Oa 7 . 03 

Lime,  CaO 62.50 

Magnesia,  MgO 2 . 06 

Sulfur  trioxide,  S03 1 .38 

Loss  on  ignition 1 . 80 

It  is  seldom  necessary,  however,  to  make  a  complete 
chemical  analysis.  A  partial  analysis  will  show  whether  the 
cement  has  been  adulterated  or  is  unsatisfactory. 

Specifications. — The  American  Society  for  Testing  Materials, 
under  specifications  C9-17,  gives  the  following  chemical  require- 
ments for  Portland  cement: 

Maximum 
Per  cent 

Loss  on  ignition 4 . 00 

Insoluble  residue 0 . 85 

Sulfur  trioxide,  S03 2.00 

Magnesia,  MgO 5 .00 

The  methods  given  herewith,  so  far  as  they  apply  to*  the 
above  determinations  are  according  to  the  American  Society  for 
Testing  Materials  requirements. 

Loss  on  Ignition, — Heat  1  gram  in  a  weighed,  covered  platinum 

*  Meade:  "  Portland  Cement "  (1906),  page  16. 


MISCELLANEOUS  ANALYSES  573 

crucible  of  20-25   cc.  capacity,   using    either  of   the  following 
methods  as  ordered: 

(A)  Place  the  crucible  in  a  hole  in  an  asbestos  board,  clamped 
horizontally  so  that  about  three-fifths  of  the  crucible  projects 
below,  and  blast  at  a  full  red  heat  for  fifteen  minutes  with  an 
inclined  flame.     Cool  in  a  desiccator  and  weigh.     Check  the  loss 
in  weight  by  a  second  blasting  for  five  minutes.     Take  care  to 
wipe  off  any  particles  of  asbestos  that  may  adhere  to  the  crucible 
when  withdrawn  from  the  asbestos  board. 

(B)  Place  the  crucible  in  a  muffle  heated  to  900-1000°  C. 
for  fifteen  minutes  and  cool  in  a  desiccator  and  weigh.     Check  the 
weight  by  a  second  heating  for  five  minutes. 

NOTE. — A  permissible  variation  of  0.25%  is  allowed  and  all  results  between 
4.00  and  4.25%  shall  be  reported  as  4.00%,  when  the  cement  is  bought  to 
A.  S.  T.  M.  specifications. 

Insoluble  Residue. — Treat  1  gram  of  the  sample  in  a  beaker 
with  10  cc.  of  water  and  5  cc.  of  cone.  HC1  and  warm  until  effer- 
vescence ceases.  Dilute  to  50  cc.  and  digest  on  the  steam  bath 
or  hot  plate  until  decomposition  is  complete.  Filter  the  residue 
and  wash  with  cold  water.  Digest  the  filter  paper  and  contents 
in  about  30  cc.  of  a  5%  solution  of  Na2CO3,  keeping  the  liquid 
at  just  below  boiling  for  fifteen  minutes.  Filter  this  residue,  wash 
with  cold  water,  then  with  a  few  drops  of  hot  HC1  (1  *  9)  and 
finally  with  hot  water.  Ignite  at  red  heat,  cool  in  a  desiccator 
and  weigh. 

NOTE. — A  permissible  variation  of  0.15%  will  be  allowed  and  all  results 
between  0.85  and  1.00%  shall  be  reported  as  0.85%,  when  the  cement  is  pur- 
chased to  A.  S.  T.  M.  specifications. 

Sulfur  Trioxide. — If  the  insoluble  residue  has  been  determined, 
use  the  acid  filtrate  for  the  determination  of  SOs.  Otherwise, 
dissolve  1  gram  of  the  cement  in  10  cc.  of  HC1  (1:1)  with  gentle 
warming.  When  the  solution  is  complete,  add  40  cc.  of  water. 
Filter  and  wash  the  residue  thoroughly  with  water.  Dilute  to 
250  cc.,  heat  to  boiling  and  add  10  cc.  of  a  hot  10%  solution  of 
BaCl2,  slowly,  drop  by  drop,  from  a  pipette,  and  continue  boiling 
for  fifteen  minutes.  Digest  on  the  steam  bath  until  the  pre- 
cipitate has  settled.  Filter  and  wash  with  hot  water.  Place  the 
paper  and  contents  in  a  weighed  platinum  crucible  and  slowly  char 


574  TECHNICAL  METHODS  OF  ANALYSIS 

the  paper  until  consumed  without  burning.  Then  ignite,  cool 
in  a  desiccator  and  weigh  as  BaSC>4.  Calculate  to  80s. 

CALCULATION.— BaSO4  X  0.3430  =  SO3. 

NOTE. — A  permissible  variation  of  0.10%  will  be  allowed  and  all  results 
between  2.00  and  2.10%  shall  be  reported  as  2.00%,  when  the  cement  is  pur- 
chased to  A.  S.  T.  M.  specifications. 

Silica. — Place  0.5  gram  of  the  cement  in  an  evaporating  dish, 
add  10  cc.  of  water  to  prevent  lumping  and  then  10  cc.  of  cone. 
HC1.  Heat  gently  and  agitate  until  decomposition  is  complete. 
Then  evaporate  to  complete  dry  ness  on  the  steam  bath.  Heat 
the  residue  to  about  150°  C.  for  one-half  to  one  hour.  Take  up 
with  20  cc.  of  HC1  (1  :  1),  cover  the  dish  and  digest  for  ten  min- 
utes on  the  steam  bath.  Dilute  and  filter  through  a  quantitative 
filter,  washing  thoroughly  with  hot  water.  Evaporate  the  filtrate 
again  to  dryness  on  the  steam  bath.  Take  up  with  HC1  (1:1), 
digest  for  ten  minutes  on  the  steam  bath  and  filter  through  a 
fresh  quantitative  filter,  washing  with  hot  water.  Place  both 
papers  in  a  weighed  platinum  crucible,  dry,  blast  to  constant 
weight  and  weigh  as  SiO2- 

NOTE. — If  the  silica  determination  is  not  required,  it  is  not  necessary  to 
make  the  second  evaporation,  nor,  of  course,  to  weigh  the  SiCV 

Iron  Oxide  and  Alumina. — To  the  filtrate  from  the  SiO2  deter- 
mination (about  250  cc.),  add  5  cc.  of  cone.  HC1  and  sufficient 
bromine  water  to  precipitate  any  Mn  which  may  be  present. 
Make  alkaline  with  NH40H,  and  boil  until  the  odor  of  NH3 
is  nearly  but  not  quite  gone.  Let  the  precipitate  settle  and 
wash  once  by  decantation  and  then  slightly  on  the  filter  paper. 
Set  aside  the  filtrate  and  transfer  the  precipitate  by  a  jet  of  hot 
water  to  the  original  beaker.  Dissolve  in  10  cc.  of  hot  HC1  and 
extract  the  filter  paper  with  acid,  adding  the  solution  and  wash- 
ings to  the  main  solution.  Then  reprecipitate  the  iron  and  alumina 
at  boiling  heat  by  NH4OH  and  bromine  water  in  a  volume  of 
about  100  cc.  Collect  the  precipitate,  washing  on  the  filter 
previously  used,  if  this  is  still  intact.  Transfer  to  a  weighed 
platinum  crucible,  ignite  in  a  blast  lamp,  cool  and  weigh. 

The  above  precipitate  consists  of  Fe2OsH-Al2O3+Mn3O4. 
For  general  purposes  it  is  sufficient  to  report  this  as  "  iron  oxide 
and  alumina."  If  desired,  the  amounts  of  Fe20a  and  Mn304 
may  be  determined  and  subtracted  from  the  total  precipitate  to 


MISCELLANEOUS  ANALYSES  575 

determine  the  amount  of  A^Os-  The  amount  of  Mn  is  generally 
insignificant,  and  the  iron  may  be  determined  by  fusing  the  ignited 
precipitate  with  KHSCU  and  passing  the  solution  of  the  fusion 
(made  acid  with  fl^SCU)  through  a  Jones  reductor,  titrating  the 
iron  with  standard  KMnO4  solution.  (See  page  148.) 

Lime. — To  the  combined  filtrates  from  the  iron  and  alumina, 
somewhat  evaporated  if  necessary,  add  1  cc.  of  cone.  NH4OH, 
heat  to  boiling  and  add  25  cc.  of  a  saturated,  boiling  solution  of 
(NH4)2C2C>4.  Boil  until  the  precipitate  settles  well,  let  stand 
for  one  hour,  filter  and  wash  with  hot  water.  Place  the  filter 
while  still  wet  in  a  platinum  crucible  (unweighed)  and  burn  off 
the  paper  over  a  low  flame,  finally  igniting  until  the  paper  is 
consumed.  Dissolve  this  residue  in  HC1  and  dilute  to  100  cc. 
Add  NH^OH  in  slight  excess,  heat  to  boiling  and  reprecipitate  the 
lime  with  (NH4)2C204,*  let  stand  until  settled  clear;  then  filter 
and  wash  with  hot  water. 

The  precipitate  of  CaC2O4  may  be  dissolved  in  H2SO4  and 
titrated  hot  with  0.1  N  KMnO4  (see  page  326)  or  ignited  strongly 
in  a  weighed  platinum  crucible,  cooled  in  a  desiccator  and  weighed 
rapidly  as  CaO. 

Magnesia. — To  the  combined  filtrates  from  the  CaC2O4,  add 
a  slight  excess  of  HC1,  concentrate  on  the  steam  bath  to  about 
150  cc.,  make  slightly  alkaline  with  NH4OH,  boil,  and  filter,  if 
necessary.  (There  may  be  a  slight  precipitate  of  iron  and  alumina 
and  perhaps  calcium  salts.)  When  cool,  add  10  cc.  of  a  saturated 
solution  of  NaNH4HPO4,  with  constant  stirring.  When  the 
crystalline  NH^MgPCU  has  formed,  add  a  moderate  excess  of 
cone.  NH40H.  Set  aside  for  several  hours,  preferably  overnight, 
filter  and  wash  with,  water  containing  2.5%  of  NHs.  Dissolve 
the  precipitate  in  a  small  quantity  of  HC1,  dilute  to  about  100  cc. 
and  add  1  cc.  of  a  saturated  solution  of  *NaNH4HPO4  "and  then 
cone.  NELiOH,  with  constant  stirring,  until  the  crystalline  precip- 
itate is  again  formed  and  the  NH^OH  is  in  moderate  excess.  Let 
stand  for  about  two  hours.  Filter  through  an  ignited  and  weighed 
Gooch  crucible,  washing  as  before.  Ignite  the  precipitate  to 
constant  weight  over  a  Meker  burner  or  blast  lamp  not  strong 
enough  to  soften  or  melt  the  pyrophosphate.  Cool  in  a  desiccator 
and  weigh  as  Mg2?2O7.  Calculate  to  MgO. 

CALCULATION.— Mg2P2O7X  0.3621  =  MgO. 


576  TECHNICAL  METHODS  OF  ANALYSIS 

NOTES. — (1)  A  permissible  variation  of  0.4%  will  be  allowed  and  al)  results 
between  5.00  and  5.40%  shall  be  reported  as  5.00%,  when  the  cement  is  bought 
to  A.  S.  T.  M.  specifications. 

(2)  In  case  only  the  MgO  .is  desired  all  the  steps  in  the  above  procedure 
must  be  followed  beginning  with  "  Place  0.5  gram  of  the  cement  in  an  evap- 
orating dish,"  etc.,  except  that  a  double  evaporation  of  the  silica  solution  is 
not  necessary,  nor,  of  course,  is  it  necessary  to  do  anything  with  the  iron  and 
alumina  precipitates  or  the  second  CaC2O4  precipitate. 

REFERENCE. — American  Society  for  Testing  Materials,  Triennial  Stand- 
ards (1918),  pages  506-509. 


MECHANICAL  TESTING  OF  SAND  AND  GRAVEL  FOR  USE  IN  REIN- 
FORCED CONCRETE 

General. — Sand  and  gravel  for  use  in  reinforced  concrete  con- 
struction have  been  the  subject  of  considerable  study,  but  thus  far 
no  official  specifications  for  testing  have  appeared.  The  following 
methods,  however,  have  been  used  for  some  time  in  this  laboratory 
with  good  results.  It  is  to  be  understood  that  they  apply  only  to 
material  for  use  with  cement  in  concrete  construction. 

Definitions. — (1)  SAND  OR  FINE  AGGREGATE. — This  con- 
sists of  natural  sand,  crushed  stone  or  gravel  screenings,  graded 
from  fine  to  coarse,  and  completely  passing  a  quarter-inch  screen 
in  the  dry  condition.  It  should  be  free  from  dust,  loam,  soft 
particles,  clay  lumps,  and  organic  matter.  Not  more  than  6% 
should  pass  a  100-mesh  sieve  and  it  should  be  free  from  an  excessive 
amount  of  mica. 

(2)  GRAVEL    OR     COARSE    AGGREGATE.  —  This    consists    of 
natural  gravel,  crushed  stone,  cinders,  or  slag,  graded  from  small 
to  large  particles,  none  of  which,  however,  will  pass  through  a 
quarter-inch  screen.     It  should  be  clean  and  free  from  sticks, 
leaves,  roots,  or  other  organic  matter.     Bank  gravel  should  be 
screened  on  a  quarter-inch  screen  before  mixing  in  construction 
work. 

(3)  SLAG. — When  slag  is  used  it  should  be  clean,  air-cooled 
blast  furnace  slag  weighing  not  less  than  75  Ibs.  per  cubic  foot  and 
containing  not  over  1.3%  of  sulfur  as  sulfides. 

(4)  CINDERS. — Where  cinders   are   used   as  coarse  aggregate 
they  should  be  composed  of  hard,  clean,  vitreous  clinker,  free 
from  unburned  coal  or  ashes  and  from  sulfides. 

General  Appearance. — Examine  the  sample  as  received  and 


MISCELLANEOUS  ANALYSES  577 

note  whether  or  not  it  is  clean  and  contains  any  of  the  impurities 
mentioned  above. 

Mechanical  Analysis  (Fineness). — The  sample  must  be  dry 
before  starting  screening  tests. 

COARSE  OR  MIXED  AGGREGATE. — If  the  sample  looks  as  though 
it  would  practically  all  pass  a  J-inch  sieve,  weigh  out  500  grams. 
If  it  contains  many  particles  coarser  than  J-inch,  weigh  out  a-  con- 
siderably larger  amount,  depending  upon  the  proportion  and  size 
of  the  large  particles.  For  samples  containing  particles  as  large  as 
2  inches,  as  much  as  5-10  kilograms  should  be  weighed. 

Pass  the  sample  successively  through  the  various  screens, 
beginning  with  the  largest  and  continuing  down  to  and  including 
the  J-inch  screen.  Weigh  the  residue  retained  on  each  screen. 
Calculate  the  amounts  passing  each  screen  as  follows : 

Subtract  the  amount  remaining  on  the  largest  screen  from 
the  total  amount  of  sample  weighed  out.  This  gives  the  weight 
passing  this  screen.  From  this  weight  subtract  the  amount 
remaining  on  the  next  screen.  This  gives  the  weight  passing  that 
screen.  From  the  latter  weight  subtract  the  amount  retained  on 
the  third  screen;  and  so  on.  Calculate  these  weights  to  percent- 
ages of  the  original  sample. 

Mix  that  portion  of  the  sample  which  passed  the  J-inch  screen 
and  weigh  out  200  grams.  Make  sieving  tests  on  this  as  described 
below  under  Sand. 

NOTES. — (1)  The  screens  generally  used  for  coarse  aggregate  are  3£,  3, 
2£,  2,  l\,  1,  f,  £,  and  Hnch,  respectively.  They  should  have  square  openings 
of  uniform  size.  The  above  figures  refer  to  the  size  of  the  openings;  the 
1-inch  screen,  for  example,  has  openings  1  inch  square. 

(2)  The  screening  tests  on  the  screens  of  Hnch  and  larger  are  calculated 
on  the  sample  as  received,  whereas  the  figures  on  sieves  smaller  than  J-inch 
should  be  calculated  on  the  basis  of  the  sand  (material  finer  than  |-inch) . 

(3)  The  Hnch  sieve  is  taken  as  the  dividing  line  between  sand  and  gravel. 

SAND. — If  the  sample  is  all  finer  than  J-inch,  weigh  out  200 
grams;  otherwise  weigh  out  200  grams  of  the  material  which  has 
passed  a  J-inch  sieve.  Place  it  on  a  6-mesh  sieve  which  is  the  top- 
most of  a  series  of  7  brass  sieves  fitting  into  each  other  to  form  a 
nest.  The  other  sieves  in  the  nest  are  8,  10,  20,  30,  50,  and  100- 
mesh,  respectively.  Put  the  cover  on  the  top  sieve  and  a  receiver 
under  the  bottom  one,  and  place  the  nest  in  a  Ro-tap  mechanical 


578 


TECHNICAL  METHODS  OF  ANALYSIS 


sieving  machine.  After  five  minutes'  sieving,  remove  and  weigh 
the  residue  in  the  bottom  pan  (passing  100-mesh).  Return  the 
pan  and  continue  sieving  for  five  minutes  longer.  Continue  this 
until  the  increase  in  the  amount  of  the  fine  residue  in  the  pan  is 
not  more  than  1  gram  between  subsequent  shakings.  Finally 
weigh  the  residue  on  each  sieve  and  calculate  the  percentage 
passing  each  mesh  as  previously  described. 

The  following  example  shows  the  method  of  tabulating  the 
figures  and  the  form  of  the  final  report.  The  figures  to  be  reported 
are  in  the  last  column. 

SCREENING  TEST  OF  SAMPLE  AS  RECEIVED   (5000  GRAMS  TAKEN) 


Screen 

Grams  Retained 

Grams  Passing 

Per  Cent  Passing 

3£  inch 

None 

5000 

100.0 

3    inch 

•      500 

4500 

90.0 

2£  inch 

750 

3750 

75.0 

2    inch 

1000 

2750 

55.0 

U  inch 

250 

2500 

50.0 

1    inch 

100 

2400 

48.0 

f  inch 

275 

2125 

42.5 

\  inch 

500 

1625 

32.5 

\  inch 

500 

1125 

22.5 

SIEVING  TEST  OF  SAND  PASSING  I-INCH  (200  GRAMS  TAKEN) 


Sieve 

Grams  Retained 

Grams  Passing 

Per  Cent  Passing 

^  inch 

None 

200 

100.0 

6-mesh 

24 

176 

88.0 

8-mesh 

33 

143 

71.5 

10-mesh 

27 

116 

58.0 

20-mesh 

35 

81 

40.5 

30-mesh 

30 

51 

25.5 

50-mesh 

21 

30 

15.0 

100-mesh 

21 

9 

4.5 

NOTES. — (1)  Some  contractors  require  also  a  200-mesh  sieve  test.     In  this 
case  use  the  cement  sieve  described  on  page  565. 

(2)  Sieving  may  be  done  by  hand,  using  the  sieves  consecutively,  always 


MISCELLANEOUS  ANALYSES 


579 


starting  with  the  largest;  but  much  time  is  saved  by  the  Ro-tap  and  it  elim- 
inates the  personal  factor  of  the  operator. 

(3)  The  sieves  used  should  be  accurately  made  and  should  be  carefully 
tested  out  unless  certified  by  the  U.  S.  Bureau  of  Standards.  The  A.  S.  T.  M. 
specifications  for  standard  sieves  *  are  as  follows: 


Permissible  Variations 

above  and  below 

Mesh 
Desig- 
nation 

Acutal  Mesh 
(per  inch) 

Opening 
(inch) 

WireDiam. 

(inch) 

Standard 

Mesh 

Diameter 

(per  inch) 

(inch) 

10 

9.9 

0.079 

0.022 

0.1 

0.002 

20 

20.3 

0.0335 

0.0157 

0.5 

0.0006 

30 

30.5 

0.0197 

0.0130 

1.0 

0.0005 

40 

40.6 

0.0142 

0.0102 

1.5 

0.0004 

50 

50.8 

0.0114 

0.0083 

2.0 

0.0004 

80 

78.7 

0.0067 

0.0059 

3.0 

0.0003 

100 

99.1 

0.0055 

0.0046 

3.0 

0.0003 

200 

200.7 

0.0029 

0.0021 

8.0 

0.0002 

Tensile  Strength. — Make  up  seven  1  :  3  mortar  briquettes 
with  standard  Ottawa  sand  and  any  of  the  standard  brands  of 
Portland  cement,  f  as  described  on  page  569  under  Tensile 
Strength. 

Make  up  seven  more  briquettes  using  the  same  cement,  but, 
instead  of  standard  Ottawa  sand,  use  the  sand  in  question  (after 
removing  any  material  coarser  than  J  inch).  Both  sets  of  bri- 
quettes should  be  made  up  to  standard  mortar,  based  on  the 
normal  consistency  of  the  cement  used,  and  the  per  cent  of  water 
used  should  be  stated.  In  the  case  of  bank  sand  or  crushed 
stone  containing  considerable  fine  material,  it  will  be  found  that 
more  water  is  required  to  make  a  mortar  of  the  proper  consistency 
than  in  the  case  of  the  standard  Ottawa  sand. 

Break  3  briquettes  of  each  set  at  the  end  of  seven  days  and 

*  American  Society  for  Testing  Materials:  Triennial  Standards  (1918), 
page  663. 

f  The  cement  should  be  tested  according  to  A.  S.  T.  M.  specifications 
(see  page  561),  and  not  used  if  it  does  not  meet  these  specifications. 


580  TECHNICAL  METHODS  OF  ANALYSIS 

3  at  the  end  of  twenty-eight  days,  respectively.  The  fourth 
briquette  of  the  28-day  sets  is  only  to  be  broken  in  case  any- 
thing goes  wrong  with  one  of  the  other  three  [see  page  571, 
under  Note  (1)].  Divide  the  average  strength  of  the  sample 
briquettes  by  the  average  strength  of  the  standard  sand  briquettes 
broken  at  the  same  time,  and  multiply  by  100  to  obtain  the  per- 
centage strength. 

The  following  example  shows  the  method  of  reporting: 

Tensile  Strength,  Ibs.  per  square  inch: 

1  cement:  3  sand 
Seven  days 248-270-264 

Average 261 

Twenty-eight  days 380-340-355 

Average 358 

Per  cent  of  water  used 11 . 0% 

1  cement:  3  standard  sand 
Seven  days 238-258-250 

Average 259 

Twenty-eight  days 370-328-341 

Average 346 

Per  cent  of  water  used 10 . 2% 

Percentage  Strength  of  Standard  Sand: 

Seven  days 105% 

Twenty-eight  days 103% 

NOTES. — (1)  A  well-graded,  clean  sand  should  show  a  tensile  strength 
more  than  100%  that  of  the  standard  sand  at  both  periods.  It  is  usually 
recommended  that  a  sand  which  shows  less  than  70%  of  the  standard  sand's 
strength  at  the  end  of  twenty-eight  days  should  be  rejected  for  use  in 
reinforced  concrete  work.  A  satisfactory  sand  should  also  show  a  greater 
actual  strength  at  the  end  of  twenty-eight  days  than  at  the  end  of  seven  days. 

(2)  Any  obviously  defective  briquette  should  not  be  counted  in  the  average 
nor  any  result  which  varies  more  than  50  Ibs.  from  the  average. 

Color  Test  for  Organic  Matter. — The  method  is  based  on  a 
comparison  of  the  color  produced  by  the  reaction  of  NaOH  upon 
the  organic  matter  in  the  sand  with  standard  colors  produced 
from  known  amounts  of  alkaline  sodium  tannate. 

To  200  grams  of  the  dry  sample  (passing  J-inch),  add  100  cc. 
of  3%  NaOH  solution  and  digest  at  room  temperature  with 
occasional  stirring  for  twenty-four  hours.  Filter  and  refilter,  if 


MISCELLANEOUS  ANALYSES 


581 


necessary,  until  the  filtrate  is  absolutely  clear.  Place  10  cc.  of  the 
final  clear  filtrate  in  a  50  cc.  Nessler  tube  and  dilute  to  50  cc. 
with  distilled  water.  Mix  thoroughly  and  let  stand  until  all  foam 
and  bubbles  disappear.  Determine  the  color  value  of  the  liquid 
by  comparing  it  with  tubes  containing  standard  solutions  of 
alkaline  sodium  tannate,  looking  through  the  full  depth  of  the 
solution  with  the  cylinders  held  toward  a  good  natural  light. 

Standard  Tannate  Solution. — The  preparation  of  the  standard 
solution  for  comparing  the  colors  should  be  begun  at  the  same  time 
as  the  treatment  of  the  sand.  Add  10  cc.  of  a  2%  solution  of 
tannic  acid  in  10%  alcohol  to  90  cc.  of  a  3%  solution  of  NaOH 
and  let  stand  twenty-four  hours  at  room  temperature.  Place 
1,  2,  3,  4,  5,  6,  7,  8,  9,  and  10  cc.,  respectively,  of  this  solution  in 
50  cc.  Nessler  tubes,  dilute  to  the  mark  with  distilled  water  and 
mix. 

The  following  table  shows  the  amount  of  tannic  acid  in  each 
cylinder  and  the  color  value  of  the  solution  expressed  in  parts  of 
tannic  acid  per  million  parts  by  weight : 


Tannate  Solution 
cc. 

Tannic  Acid 
mgs. 

Color  Value 

1 

2 

100 

2 

4 

200 

3 

6 

300 

4 

8 

400 

5 

10 

500 

6 

12 

600 

7 

14 

700 

8 

16 

800 

9 

18 

900 

10 

20 

1000 

It  is  desirable  to  have  good  sunlight  for  comparing  the  colors. 
If  sunlight  is  not  available  the  amount  of  tannic  acid  in  each  of  the 
standard  tubes  may  be  decreased  by  one-half  and  the  other  values 
of  the  table  modified  accordingly. 

In  case  the  solution  obtained  by  digesting  the  sand  with  the 
NaOH  is  very  dark,  use  less  than  10  cc.  for  the  comparison,  and 
make  the  necessary  modifications  in  the  calculation.  With  very 


582  TECHNICAL  METHODS  OF  ANALYSIS 

light-colored  solutions,  use  more  than  10  cc.  of  the  filt  ate.  The 
depth  of  the  color  of  the  solution  decreases  on  standing,  and,  there- 
fore, the  solution  should  be  made  up  fresh  for  each  day's  work. 
CALCULATION. — Using  10  cc.  of  the  filtrate  from  the  200-gram 
sample,  the  color  value  of  the  sand  is  the  same  as  that  of  the 
standard  tube  which  it  most  nearly  matches.  If  5  cc.  of  the  fil- 
trate are  used,  the  color  values  should  be  doubled.  Similar  cor- 
rections should  be  made  if  any  other  volume  than  10  cc.  is  em- 
ployed. 

NOTES. — (1)  This  color  test  was  developed  by  Abrams  and  Harder, 
published  in  Circular  No.  1,  Structural  Materials  Research  Laboratory,  Lewis 
Institute,  Chicago,  (1917). 

(2)  Sand  showing  a  color  value  greater  than  250  should  be  looked  upon 
with  suspicion  for  use  in  reinforced  concrete.  Most  good  sands  give  color 
values  between  0  and  100. 


TABLES 

IN  the  following  tables  the  weights  and  calculations  are  based 
on  the  table  of  International  Atomic  Weights  for  1920.  In  com- 
puting the  molecular  weights  in  Table  I  the  number  of  decimal 
places  has  been  governed  by  the  least  number  of  decimal  places  in 
any  one  of  the  atomic  weights  of  the  elements  entering  into  the 
chemical  formula.  For  example,  in  the  case  of  H^PtCle  the  cal- 
culated molecular  weight  would  be  2X1.008+195.2+6X35.46  = 
409.976.  Since,  however,  the  atomic  weight  of  Pt  is  given  only 
to  one  decimal  place,  the  molecular  weight  of  the  compound  should 
also  contain  only  one  decimal  place  and  therefore  will  be  found  in 
table  I  as  410.0.  In  the  tables  of  equivalents  of  volumetric  solu- 
tions the  values  have,  in  most  cases,  been  carried  out  to  a  sufficient 
number  of  places  to  give  an  accuracy  of  at  least  0.1%;  and  for 
purposes  of  uniformity  the  factors  in  Table  III  have,  as  a  rule, 
been  calculated  to  four  decimal  places.  In  a  few  cases,  where  the 
values  are  more  or  less  approximate  or  empirical,  they  are  carried 
to  a  lesser  number  of  decimal  places. 

Five-place  logarithms  have  been  used  throughout  the  tables 
for  uniformity  and  greater  accuracy.  In  most  cases,  however, 
sufficient  accuracy  would  be  obtained  from  four-place  logarithms 
and  the  analyst  is  advised  to  "round  off"  the  last  place  of  the 
logarithms  given,  unless  unusual  accuracy  is  required. 

583 


584 


TECHNICAL  METHODS  OF  ANALYSIS 


TABLE  I 
INTERNATIONAL  ATOMIC  WEIGHTS,  1920 


Element 


Symbol 


Atomic 
Weight 


Logarithm 


Aluminum Al 

Antimony Sb 

Argon A 

Arsenic As 

Barium Ba 

Bismuth Bi 

Boron B 

Bromine Br 

Cadmium Cd 

Caesium Cs 

Calcium Ca 

Carbon C 

Cerium Ce 

Chlorine Cl 

Chromium Cr 

Cobalt Co 

Columbium ^ Cb 

Copper Cu 

Dysprosium Dy 

Erbium Er 

Europium Eu 

Fluorine F 

Gadolinium Gd 

Gallium Ga 

Germanium Ge 

Glucinum Gl 

Gold Au 

Helium He 

Holmium Ho 

Hydrogen H 

Indium In 

Iodine , I 

Iridium Ir 

Iron Fe 

Krypton Kr 

Lanthanum La 

Lead Pb 

Lithium -. . Li 

Lutecium Lu 

Magnesium Mg 

Manganese Mn 


27.1 

120.2 
39.9 
74.96 

137.37 

208.0 
10.9 
79.92 

112.40 

132.81 
40.07 
12.005 

140.25 
35.46 
52.0 
58.97 
93.1 
63.57 

162.5 

167.7 

152.0 
19.0 

157.3 

70.1 

72.5 

9.1 

197.2 
4.00 

163.5 
1.008 

114.8 

126.92 

193.1 
55.84 
82.92 

139.0 

207.20 
6.94 

175.0 
24.32 
54.93 


1.43297 
2 . 07990 
1.60097 
1 . 87483 
2.13789 
2.31806 
1.03743 
1.90266 
2.05077 
2.12323 
1.60282 
1.07936 
2.14691 
1.54974 
1 . 71600 
1.77063 
1 . 96895 
1.80325 
2.21085 
2 . 22453 
1 . 18184 
1.27875 
2.19673 
1.84572 
1.86034 
0.95904 
2.29491 
0 . 60206 
2.21352 
0.00346 
2.05994 
2.10353 
2.28578 
1.74695 
1.91866 
2.14301 
2.31639 
0.84136 
2.24304 
1 . 38596 
1 . 73981 


TABLES 


585 


TABLE  I — INTERNATIONAL  ATOMIC  WEIGHTS,  1920 


Element 


Symbol 


Atomic 
Weight 


Logarithm 


Mercury Hg 

Molybdenum Mo 

Neodymium Nd 

Neon Ne 

Nickel Ni 

Niobium Nb 

Niton  (radium  emanation) Nt 

Nitrogen N 

Osmium Os 

Oxygen O 

Palladium Pd 

Phosphorus P 

Platinum Pt 

Potassium K 

Praseodymium Pr 

Radium Ra 

Rhodium Rh 

Rubidium Rb 

Ruthenium Ru 

Samarium Sa 

Scandium Sc 

Selenium Se 

Silicon Si 

Silver Ag 

Sodium Na 

Strontium Sr 

Sulfur S 

Tantalum Ta 

Tellurium Te 

Terbium .  Tb 

Thallium Tl 

Thorium Th 

Thulium Tm 

Tin Sn 

Titanium Ti 

Tungsten W 

Uranium U 

Vanadium V 

Xenon Xe 

Ytterbium  (Neoytterbium) Yb 

Yttrium Yt 

Zinc Zn 

Zirconium.  .  Zr 


200.6 
96.0 

144.3 
20.2 
58.68 


2.30233 
1.98227 
2.15927 
1.30535 
1.76849 


(See  Columbium) 


222.4 

14.008 
190.9 

16.000 
106.7 

31.04 
195.2 

39.10 
140.9 
226.0 
102.9 

85.45 
101.7 
150.4 

44.1 

79.2 

28.3 
107.88 

23.00 

87.63 

32.06 
181.5 
127.5 
159.2 
204.0 
232.15 
168.5 
118.7 

48.1 
184.0 
238.2 

51.0 
130.2 
I'K.S 

89.33 

65.37 

90.6 


2.34713 
1 . 14638 
2.28081 
1.20412 
2.02816 
1.49192 
2.29048 
1.59218 
2 . 14891 
2.35411 
2.01242 
1.93171 
2.00732 
2.17725 
1 . 64444 
1.89873 
1.45179 
2.03294 
1 . 36173 
1.94265 
1.50596 
2.25888 
2 . 10551 
2 . 20194 
2.30963 
2.36577 
2.22660 
2.07445 
1.68215 
2.26482 
2.37694 
1.70757 
2.11461 
2.23930 
1.95100 
1.81538 
1 . 95713 


586  TECHNICAL  METHODS  OF  ANALYSIS 

TABLE  II 
MOLECULAR  AND  ATOMIC-GROUP  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Acetaldehyde 

CH3CHO 

44  042 

64387 

(Acetate  Radical)  

59  034 

77110 

Acetone 

(CH3)2CO 

58  063 

76390 

Acetic  Anhydride  
(Acetyl    Radical)  ... 

(CH3CO)2O  
C2H3O 

102.068 
43  034 

.00888 
63381 

Acetylene  

26  026 

41541 

Acid,  Abietic  

302  34 

2  48050 

Acetic 

HC2H3O2 

60  042 

1  77845 

Arachidic  

312  42 

2  49474 

Arsenic 

H3AsO4-£H2O 

150  99 

2  17895 

Arsenic,  Anhyd  

H3AsO4  

141  98 

2  15223 

Benzoic  

HC7H5O2 

122  083 

2  08666 

Bichromic 

H2Cr2O7 

218  0 

2  33846 

Boric  

H3BO3 

61  9 

1  79169 

Butyric 

HC4H7O2 

88  084 

1  94490 

Carbonic  

H2CO3  .  .  . 

62  021 

1  79254 

Chlorauric,  Anhyd 

HAuCL, 

340  0 

2  53148 

Chlorauric,  Cryst  
Chloric,  Anhyd  

HAuCl4-4H2O  
HC1O3 

412.1 

84  47 

2.61500 
1  92670 

Chloric    Cryst  . 

HC1O3  •  7H2O 

210  58 

2  32342 

Chlorplatinic,  Anhyd.  .  .  . 

H2PtCl6 

410  0 

2  61278 

Chlorplatinic,  Cryst 

H2PtCl6  •  6H2O 

518  1 

2  71441 

Chlorplatinous 

H2PtCl4 

339  1 

2  53033 

Chromic  

H2CrO4 

118  0 

2  07188 

Citric,  Anhyd 

H3C6H5O7 

192  09 

2  28351 

Citric,  Cryst  
Fluosilicic    .  . 

H3C6H507-H20  
H2SiF6 

210.11 
144  3 

2.32245 
2  15927 

Formic  

HCHO2  

46  021 

1  66296 

Hydriodic   : 

HI 

127  93 

2  10697 

Hydrobromic 

HBr 

80  93 

1  90811 

Hydrochloric  

HC1  

36  47 

1  56194 

Hydrocyanic 

HCN 

27  021 

1  43171 

Hydrofluoric 

HF 

20  0 

1  30103 

lodic  

HIO3  

175  93 

2  24534 

Lactic 

HC3H5O3 

90  063 

1  95455 

Malic  

134  068 

2  12732 

Molybdic,  Anhyd 

H2MoO4  . 

162  0 

2  20952 

Molybdic,  Hydrated  
Nitric  

H2MoO4-H2O  
HNO3  

180.0 
63  016 

2.25527 
1  79945 

TABLES 


587 


TABLE  II — MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Acid    Nitrous 

HNO2 

47  016 

1  67224 

Oleic 

282  36 

2  45080 

Oxalic,  Anhyd.  .  .  .  

H2C2O4  . 

90.026 

1.95437 

Oxalic   Cryst        

H2C2O4-2H2O. 

126  058 

2  10057 

Palmitic  

HCi6HsiO2  

256.34 

2.40882 

Perchloric,  Anhyd  

HC1O4  

100.47 

2.00204 

Perchloric,  Cryst  
Persulfuric  

HC1O4-2H2O  
H2S2O8  

136.50 
194.14 

2.13513 

2.28812 

Phosphoric   Hypo- 

H2PO3 

81  06 

1  90881 

Phosphoric,  Meta-  

HPO3  

80.05 

1  90336 

Phosphoric,  Ortho-  . 

H3PO4  

98  06 

1  99149 

Phosphoric   Pyro- 

H4P2O7 

178  11 

2  25069 

Phosphorous,  Hypo-  

H3PO2  

66.06 

1  .  81994 

Phosphorous,  Ortho-. 

H3PO3  

82.06 

1  91413 

Phosphotungstic 

P2O5-12WO3-42H2O 

3682  8 

3  56618 

Prussic  (see  Hydrocyanic) 
Pyrosulfuric  
Salicylic 

H2S2O7  
HC7H5O3  . 

178.14 
138  083 

2.25076 
2  14014 

Selenic   Anhyd 

H2SeO4 

145  2 

2  16197 

Selenic,  Cryst  
Selenious         

H2SeO4-H20  
H2SeO3.... 

163.2 
129  2 

2.21272 
2  11126 

Silicic   Meta- 

H2SiO3 

78  3 

1  89376 

Silicic,  Ortho-  

H2Si04  

96.3 

1.98363 

Silicotungstic  

4H2SiO3'12WO3- 

Stearic 

22H20  

3494.6 

284  38 

3.54340 
2  45390 

Sulfocyanic  

HCNS  

59  08 

1  77144 

Sulfuric            .  . 

H2SO4  

98  08 

1  99158 

Sulfurous 

H2SO3 

82  08 

1  91424 

Tannic  

322.15 

2  50806 

Tartaric,  Anhyd  
Tartaric   Cryst 

xi^^-^-H^Oe  

H2C4H4O6-H2O 

150.068 
168  084 

2.17629 
2  22553 

Tungstic 

H2WO4 

250  0 

2  39794 

Alum           

K2A1,(SO4)4-24H2O 

949.0 

2.97727 

Alumina  (see  Aluminum  Oxide) 
Aluminum  Acetate  .  . 

A1(C2H3O2)3... 

204  2 

2  31006 

Aluminum  Chloride  Anhyd 

A1C13  . 

133  5 

2  12548 

Aluminum  Chloride,  Cryst  

A1C13-6H2O  

241  6 

2  38310 

Aluminum  Fluoride,  Anhyd  .  .  . 

A1F3  

84  1 

1  92480 

Aluminum  Fluoride,  Cryst  

A1F3-3|H2O  

147.2 

2.16791 

Aluminum  Hydroxide  

A1(OH)3  

78.1 

1.89265 

588 


TECHNICAL  METHODS  OF  ANALYSIS 
TABLE  II — MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Aluminum  Oleate         

Al(Ci8H33O2)3 

871  2 

2  94012 

Aluminum  Oxide 

A12O3 

102  2 

2  00945 

Aluminum  Phosphate.  . 

A1P04.. 

122.1 

2.08672 

Aluminum  Potassium  Fluoride  (See  Potassium  Aluminum  Fluoride) 
Aluminum  Potassium  Silicate  (See  Potassium  Aluminum  Silicate) 


Aluminum  Potassium  Sulfate  (Se 
Aluminum  Silicate  

e  Alum) 
Al2Si2O7-H2O  

240  8 

2  38166 

Aluminum  Sulfate  Anhyd 

A12(SO4)3 

342  4 

2  53453 

Aluminum  Sulfate,  Cryst  
(Amino  Radical)  « 

A12(SO4)3-18H2O.... 
NH2     

666.7 
16  024 

2  .  82393 
1  20477 

Ammonia 

NH3 

17  032 

1  23126 

(Ammonium  Kadical)  

NH4           

18  040 

1  25624 

Ammonium  Acetate 

NH4C2H3O2 

77  074 

1  88691 

Ammonium  Alum  

(NH4)oAl2(SO4)4- 

24H2O  

906  9 

2  95756 

Ammonium  Bichromate  

(NH4)2Cr2O7  

252.1 

2  40157 

Ammonium  Bromide  

NH4Br     

97  96 

1  99105 

Ammonium  Carbonate 

(NH4)2CO3- 

Ammonium  Carbonate,  Cryst  .  .  '. 
Ammonium  Chloride  
Ammonium  Chlorplatinate  .... 

NH4CO2-NH2.... 
(NH4)2C03-H20.... 
NH4C1  
(NH4),PtCl6  

174.154 
114.101 
53.50 
444  0 

2.24094 
2.05729 
1.72835 
2  64738 

Ammonium  Chromate 

(NH4)2CrO4 

152  1 

2  18213 

Ammonium  Chrome  Alum  
Ammonium  Citrate  

(NH4)2Cr2(S04)4- 
24H/3  
(NH4)3C6H607  

956.7 
243.19 

2.98078 
2.38594 

Ammonium  Citrate  
Ammonium  Copper  Chloride   (S 
Ammonium  Ferric  Alum  (See  Fe 
Ammonium  Ferrous  Sulfate  (See 
Ammonium  Fluoride 

24H2O  
(NH4)3C6H607  
ee  Cupric  Ammoniui 
rric  Ammonium  Alum 
Ferrous  Ammonium 
NH4F         

956.7 
243.19 
n  Chloride 
) 
Sulfate) 
37.0 
35.048. 
144.96 
0 

2.98078 
2.38594 
) 

1.56820 
1.54466 
2.16125 

Ammonium  Hydroxide  
Ammonium  Iodide 

NH4OH  

NTU 

Ammonium  Iron  Alum     (See  Ferric  Ammonium  Alun 

Ammonium  Magnesium  Chloride,  etc.     (See  Magnesium  Ammonium 


Chloride,  etc.) 
Ammonium  Molybdate  
Ammonium  Nickel  Chloride  (See 
Ammonium  Nitrate 

(NH4)2MoO4  

196.1 
Chloride) 
80.048 
299.39 
124  .  090 
142.106 

2.29248 

1.90335 
2.47624 
2  .  09374 
2.15261 

Nickel  Ammonium  C 
NH4NO3 

Ammonium  Oleate 

NH4Ci8H33O2  

Ammonium  Oxalate,  Anhyd  .... 
Ammonium  Oxalate,  Cryst  

(NH4)2C204  
(NH4)2C204-H20... 

TABLES 
TABLE  II — MOLECULAR  WEIGHTS 


589 


Name 

Formula 

Molecular 
Weight 

Logarithm 

(Ammonium  Oxide  Radical)  .... 
Ammonium  Persulfate  

(NH)2O  

52.080 
228.20 
132.13 
115.10 

1860.1 

1877.2 
137.09 

209.14 
132.14 
51.11 
68.14 
76.11 
Dsphate) 
130.147 
88.121 
93.094 
242.6 
171.7 
297.5 
400.7 
320.4 
304.4 
226.6 
288.4 
336.6 
imonyl  Tar 
150.105 
138.96 
261.92 
214.04 
310.22 
229.92 
122.96 
181.34 
77.98 
197.92 

1.71667 
2.35832 
2.12100 
2.06108 

3.26953 
3.27351 
2.13701 

2.32043 
2.12103 
1.70851 
1.83340 
1.88144 

2.11444 
1.94508 
1.96892 
2.38489 
2.23477 
2.47349 
2.60282 
2.50569 
2.48344 
2.35526 
2.46000 
2.52711 
trate) 
2.17639 
2.14289 
2.41817 
2.33049 
2.49167 
2.36158 
2.08977 
2.25850 
1.89198 
2.29649 

(NH4)2S2O8 

Ammonium  Phosphate,  Di-  
Ammonium  Phosphate,  Mono-.  . 
Ammonium  Phosphomolybdate, 
Di-  

(NH4)2HP04  
NH4H2P04  

(NH4)2HPO4- 
12MoO3.    .    . 

Ammonium    Phosphomolybdate, 
Tri-  

(NH4)3PO4.12MoO3 
NH4NaHPO4 

Ammonium    Sodium    Hydrogen 
Phosphate,  Anhyd  
Ammonium     Sodium     Hydrogen 
Phosphate,  Cryst  

NH4NaHPO4-4H2O 

(NH4)2SO4.  

Ammonium  Sulfate  
Ammonium  Sulf  hydrate  
Ammonium  Sulfide  

NH4SH  

(NH4)2S.    .    . 

Ammonium  Sulfocyanate  
Ammonium  Zinc  Phosphate  (See 
Amyl  Acetate.  .  .  . 

NH4CNS  

Zinc  Ammonium  Ph< 

Amyl  Alcohol  

C6HnOH 

Aniline  
Antimonic  Oxychloride  

C6H6.NH2  
SbOCl3.. 

Antimonous  Oxychloride  
Antimony  Pentachloride  . 

SbOCl  . 

SbClg 

Antimony  Pentasulfide 

Sb2S6 

Antimony  Pentoxide  

Sb2O6.  . 

Antimony  Tetroxide  
Antimony  Trichloride  
Antimony  Trioxide  

Sb204  
SbCl3  

Sb2O3  .  . 

Antimony  Trisulfide  

Sb2S3 

Antimonyl  Potassium  Tartrate 
Arabinose 

(See  Potassium  Ant 

(Arsenate  Radical)  

AsO4  

(Arsenate  Radical,  Pyro-)  
Arsenic  Disulfide  

As2O7 

As2S2 

Arsenic  Pentasulfide 

As2S5 

Arsenic  Pentoxide  

As2O5  .... 

(Arsenite  Radical)  
Arsenous  Chloride 

AsO3 

AsCl3 

Arsenous  Hydride  .  
Arsenous  Oxide  

AsH3  
As2O3  .... 

590 


TECHNICAL  METHODS  OF  ANALYSIS 
TABLE  II — MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Arsenous  Sulfide  
Arsine  (See  Arsenous  Hydride) 
Auric  Chloride,  Anhyd  

As2S3  
AuCl3  

246.10 

303.6 
339.6 
197.38 
208.29 
244.32 
253.4 
279.7 
171.39 
315.51 
261.39 
153  .  37 
169.37 
313.50 
602  .  19 
233.43 
169.43 
78.078 
77.070 
155.6 
61.013 
216.0 
394.0 
484.1 
259.5 
303.0 
304.0 
512.2 
464.0 

69.8 
154.194 
196  .  220 
158.152 
183.32 
219.35 
146.42 
366.24 

2.39111 

2.48230 
2.53097 
2  .  29531 
2.31867 
2.38796 
2.40381 
2.44669 
2.23399 
2.49901 
2.41729 
2  .  18574 
2.22884 
2.49624 
2.77937 
2.36816 
2.22899 
1.89253 
1.88689 
2.19201 
1.78542 
2.33445 
2.59550 
2  .  68494 
2.41414 
2.48144 
2.48287 
2.70944 
2.66652 

1.84386 
2.18806 
2  .  29274 
2  .  19907 
2.26321 
2.34114 
2.16560 
2.56377 

Auric  Chloride,  Cryst  
Barium  Carbonate 

AuCl3-2H2O. 

BaCO3 

Barium  Chloride,  Anhyd  
Barium  Chloride,  Cryst 

BaCl2  
BaCl2-2H2O  
BaCrO4  
BaSiF6  
Ba(OH)2  
Ba(OH)2-8H2O  
Ba(NO3)2  
BaO 
BaO2    . 

Barium  Chromate  

Barium  Fluosilicate  .  ... 

Barium  Hydroxide  Anhyd 

Barium  Hydroxide,  Cryst  
Barium  Nitrate 

Barium  Oxide  
Barium  Peroxide,  Anhyd  
Barium  Peroxide,  Cryst  
Barium  Phosphate,  Tri-  
Barium  Sulfate 

BaO2-8H2O  
Ba3(PO4)2 

BaSO4 

Barium  Sulfide  
Benzene 

BaS  

C6H6 

(Benzyl  Radical)  

(Biborate  Radical)  .  .    . 

B4O7 

(Bicarbonate  Radical)  

HC03  
Cr2O7  .  . 

(Bichromate  Radical)  ...    . 

Bismuth  Nitrate,  Anhyd  
Bismuth  Nitrate,  Cryst  
Bismuth  Oxy  chloride  
Bismuth  Phosphate 

Bi(NO3)s  

Bi(NO3)3-5H2O  
BiOCl 

BiPO4 

Bismuth  Sub-Nitrate  
Bismuth  Sulfide   .    . 

BiONO3-H2O  

Bi2S3 

Bismuth  Trioxide  
Bleaching  Powder  (See  Calcium  ( 
Bone  Phosphate  (See  Calcium  PI 
Borax   (See  Sodium  Tetraborate, 
Boric  Oxide   ...         .  .          .    . 

Bi2O3  

3xychloride) 
losphate,  Tri-) 
Cryst.) 
B-O3...    . 

Borneol  

C10H17OH  

CioHnC2H3O2  

(C3H7CO)2O 

Bornyl  Acetate  

Butyric  Anhydride 

Cadmium  Chloride,  Anhyd  ..... 
Cadmium  Chloride,  Cryst  
Cadmium  Hydroxide  

CdCl2  
CdCl2-2H2O  
Cd(OH)2  
CdI2  

Cadmium  Iodide  

TABLES 


591 


TABLE  II — MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Cadmium  Nitrate,  Anhyd 

Cd(NO3)2 

236  42 

2  37369 

Cadmium  Nitrate,  Cryst  

Cd(NO3)2-4H2O.  . 

308.48 

2.48923 

Cadmium  Oxide  

CdO  

128.40 

2  10857 

Cadmium  Sulfate,  Anhyd 

CdSO4 

208  46 

2  31903 

Cadmium  Sulfate,  Cryst  
Cadmium  Sulfate,  Cryst  
Cadmium  Sulfide.  ... 

CdSO4-fH2O....... 
CdSO4-4H2O  
CdS      

256.50 
280.52 
144  46 

2.40909 
2.44796 
2  15975 

Caesium  Carbonate 

Cs2CO3 

325  63 

2  51272 

Caesium  Chloride  
Caesium  Hydroxide     .  . 

CsCl  
CsOH  

168.27 
149  .  82 

2.22601 
2  17557 

Caesium  Nitrate 

CsNO3 

194  82 

2  28963 

Caesium  Sulfate  

Cs2SO4  

361  .  68 

2  .  55833 

Caffeine     

C8Hi0N4O2  

194  152 

2  28814 

Calcium  Acetate,  Anhyd 

Ca(C2H3O2)2 

158  14 

2  19904 

Calcium  Acetate,  Cryst  

Ca(C2H3O2)2-H2O..  . 

176.16 

2.24591 

Calcium  Bicarbonate  
Calcium  Bisulfite  (Meta-) 

CaH2(CO3)2  
CaS2O5  

162.10 
184  19 

2.20978 
2  26527 

Calcium  Carbide 

CaC2 

64  08 

1  80672 

Calcium  Carbonate         

CaCO3  

100.08 

2.00034 

Calcium  Chloride  Anhyd 

CaCl2  . 

110  99 

2  04528 

Calcium  Chloride,  Cryst. 
(Hexahydrate)  

CaCl2-6H2O  

219.09 

2.34062 

Calcium  Chloride,  Cryst. 
(  Mono  hydrate) 

CaCl2-H2O 

129  01 

2  11062 

Calcium.  Fluoride 

CaF2 

78  1 

1  89265 

Calcium  Hydroxide 

Ca(OH)2  

74  09 

1  86976 

Calcium  Hypochlorite,  Anhyd  .  .  . 
Calcium  Hypochlorite,  Hyd  
Calcium  Nitrate,  Anhyd  
Calcium  Nitrate,  Cryst 

Ca(ClO)2  
Ca(ClO)2-4H2O.  .  .. 
Ca(N03)2  
Ca(NO3)2-4H2O 

142.99 
215.05 
164.09 
236  15 

2.15531 
2.33254 
2.21508 
2  37319 

Calcium  Oleate  

Ca(Ci8H33O2)2  

602  .  78 

2  .  78016 

Calcium  Oxalate  Anhyd 

CaC2O4 

128  08 

2  10748 

Calcium  Oxalate,  Cryst    . 

CaC2O4-H2O  

146.10 

2.16465 

Calcium  Oxide 

CaO 

56.07 

1  .  74873 

Calcium  Oxychloride 

CaOCl2 

126  99 

2  10377 

Calcium  Peroxide  

CaO2  

72.07 

1  .  85775 

Calcium  Phosphate,  Di-,  Anhyd 

CaHPO4  

136.12 

2.13392 

Calcium  Phosphate  Di-  Cryst 

CaHPO4-2H2O 

172.15 

2  .  23591 

Calcium      Phosphate,       Mono-, 
Anhyd 

CaH4(PO4)2  

234.18 

2.36955 

592 


TECHNICAL  METHODS  OF  ANALYSIS 
TABLE  II — MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Calcium      Phosphate,       Mono-, 
Cryst       .    .      

CaH4(PO4)2-H2O.  .. 
Ca3(P04)2  
CaSiO3  

252.20 
310.29 
116.4 
606.81 
136.13 
172.16 
72.13 
120.13 
156.16 
76.13 
44.005 
28.005 
153.85 
60.005 

388.28 
172.25 
326.27 
434.37 
328.50 
568.68 
712.81 
83.46 
119.39 
408.0 
116.0 

158.4 
266.5 
103.0 
238.0 
373.1 
400.2 
152.0 
392.2 
482.3 

2.40175 
2.49177 
2.06595 
2.78306 
2.13396 
2.23593 
1.85812 
2.07965 
2.19357 
1  .  88156 
1.64350 
1.44724 
2.18710 
1.77819 

2.58915 
2.23616 
2.51358 
2.63786 
2.51654 
2.75487 
.  2.85298 
1.92148 
2.07696 
2.61066 
2.06446 

2.19976 
2.42570 
2.01284 
2.37658 
2.57183 
2.60228 
2.18184 
2.59351 
2.68332 

Calcium  Phosphate,  Tri-  
Calcium  Silicate  

Calcium  Stearate          .    .  . 

Ca(C18H3602)2  
CaSO4  

Calcium  Sulfate,  Anhyd  

Calcium  Sulfate,  Cryst  
Calcium  Sulfide 

CaS04-2H20..  
CaS 

Calcium  Sulfite,  Anhyd  

CaSO3  

Calcium  Sulfite,  Cryst  
Carbon  Bisulfide  

CaSO3-2H2O 

CS2  

Carbon  Dioxide  

CO2  

Carbon  Monoxide  

CO  

Carbon  Tetrachloride  
(Carbonate  Radical) 

CC14  
CO, 

Carborundum     (See  Silicon  Carbide) 
Caustic  Potash  (See  Potassium  Hydroxide) 
Caustic  Soda     (See  Sodium  Hydroxide) 
Ceric  Nitrate  ....                          CWNO,^  

Ceric  Oxide  
Cerous  Nitrate,  Anhyd.  . 

CeO2 

Ce(NO3)3  

Cerous  Nitrate,  Cryst  

Ce(NO3)3-6H2O.  ... 
Ce2O3  

Cerous  Oxide  

Cerous  Sulfate,  Anhyd 

Ce2(S04)3  
Ce2(SO4)3-8H2O.  ... 
C1O3...  

Cerous  Sulfate,  Cryst  

(Chlorate  Radical)  

Chloroform 

CHC13 

(Chlorplatinate  Radical)  
(Chromate  Radical)  .  .  . 

PtCl6 

CrO... 

Chrome  Alum      (See  Potassium  Chrome  Alum) 
Chrome  Orange    (See  Lead  Chromate,  Basic) 
Chrome  Yellow    (See  Lead  Chromate) 
Chromic  Chloride,  Anhyd  CrCL  

Chromic  Chloride,  Crvst  .  .  . 

CrCl3-6H2O  

Chromic  Hydroxide 

Cr(OH)3  
Cr(NO3)3  

Chromic  Nitrate,  Anhyd  
Chromic  Nitrate,  Cryst 

Cr(N03)3-7£H20... 
Cr(NO3)3-9H2O.  ... 
Cr2O3  

Chromic  Nitrate,  Cryst  

Chromic  Oxide         

Chromic  Sulfate,  Anhyd  
Chromic  Sulfate,  Cryst  

Cr2(SO4)3  

Cr2(SO4)3-5H2O.... 

TABLES 


TABLE  II— MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Chromium  Trioxide  

CrO3  

Cr(C2H302)2  
Cr(C2H3O2)2-H2O... 
CrCl2  

100.0 
170.1 
188.1 
122.9 
68.0 
148.1 
274.2 
152.178 
165.35 
109.99 
165.94 
240.91 
129.89 
237.99 
182.99 
291.08 
74.97 
155.03 
281.14 

468.63 
540.69 
oride) 
ate) 

146.093 
1014.11 

277.52 
187.54 
123.58 
221.17 
344.75 
134.49 
170.52 
97.59 
187.59 
241.63 
295.68 
79.57 

2.00000 
2.23070 
2.27439 
2.08955 
1.83251 
2.17056 
2.43807 
2.18235 
2.21841 
2.04135 
2.21995 
2.38186 
2.11358 
2.37656 
2.26243 
2.46401 
1.87489 
2.19041 
2.44892 

2.67083 
2.73295 

2.16463 
3.00609 

2.44329 
2.27309 
2.09195 
2.34473 
2.53751 
2.12869 
2.23177 
1.98941 
2.27321 
2.38315 
2.47082 
1.90075 

Chromous  Acetate,  Anhyd  
Chromous  Acetate,  Cryst  

Chromous  Chloride  

Chromous  Oxide  . 

CrO   

Chromous  Sulfate,  Anhyd  
Chromous  Sulfate,  Cryst  
Citral             

CrSO4 

CrSO4-7H2O  

C9H15-CHO  
CoCl3 

Cobaltic  Chloride 

Cobaltic  Hydroxide 

Co  (OH)  3 

Cobaltic  Oxide  

Co2O3  

Cobalto-cobaltic  Oxide  
Cobaltous  Chloride,  Anhyd  
Cobaltous  Chloride,  Cryst  
Cobaltous  Nitrate,  Anhyd 

Co3O4.  .  . 

CoCl2 

CoCl2-6H2O  
Co(NO3)2  

Cobaltous  Nitrate,  Cryst  

Co(NO3)2-6H2O.  ... 
CoO  

Cobaltous  Oxide  

Cobaltous  Sulfate,  Anhyd 

CoSO4  

Cobaltous  Sulfate  Cryst 

CoSO4-7HoO 

Copper    (See  also  Cupric  and  CL 
Copper  Arsenate,  Anhyd 

iprous) 
Cu3(AsO4)2  

Copper  Arsenate,  Cryst  

Cu3(AsO4)2-4H2O... 
Potassium  Cupric  Ch 
otassium  Cupric  Sull 
ric  Chloride) 
C9H6O2            .    . 

Copper  Potassium  Chloride  (See  '. 
Copper  Potassium  Sulfate  (See  P 
Corrosive  Sublimate   (See  Mercuj 
Coumarin 

Cupric  Aceto-arsenite 

Cu3(AsO3)2-2As2O3- 
Cu(C2H3O2)2  

Cupric  Ammonium  Chloride  .... 
Cupric  Arsenite 

CUC12-2NH4C1- 
2H2O   

CuHAsO3  
CuCO3  

Cupric  Carbonate  

Cupric  Carbonate,  Basic  
Cupric  Carbonate,  Basic  
Cupric  Chloride  Anhyd 

CuCO3-Cu(OH)2... 
2CuCO3-Cu(OH)2.  . 
CuCl2 

Cupric  Chloride,  Cryst  

CuCl2-2H2O  

Cupric  Hydroxide  

Cu(OH)2  

Cupric  Nitrate  Anhyd         .  .  . 

Cu(NO3)2  

Cupric  Nitrate,  Cryst  
Cupric  Nitrate  Cryst 

Cu(N03)2.3H20.... 
Cu(NO3)2-6H2O.... 
CuO  

Cupric  Oxide  

594 


TECHNICAL  METHODS  OF  ANALYSIS 
TABLE  II — MOLECULAK  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Cupric  Sulfate,  Anhyd      .  . 

CuSO4  

159.63 
249.71 
95.63 
80.58 
143.14 
159.20 
121.64 
26.013 
52.026 
198.142 
116.100 
383.4 
29.050 
88.084 
46.058 

964.38 
162.22 
270.32 
859.11 
106.86 
241.86 
404.00 
159.68 
177.70 
150.88 
n) 
399.86 
562.00 
207  .  86 
231.52 
295.76 
173.91 
245.97 

392.14 
115.85 
126.76 

198.82 
591.36 

2.20311 
2.39744 
1.98059 
1.90623 
2.15576 
2.20194 
2.08507 
1.41519 
1.71622 
2.29697 
2.06483 
2.58365 
1.46315 
1.94490 
1.66330 

2.98425 
2.21010 
2.43188 
2.93405 
2.02882 
2.38357 
2.60638 
2.20325 
2.24969 
2.17863 

2.60191 
2.74974 
2.31777 
2.36459 
2.47094 
2.24033 
2.39089 

2.59344 
2.06390 
2.10298 
2.29846 
2.77185 

Cupric  Sulfate,  Cryst  

CuSO4-5H>O  

Cupric  Sulfide  

CuS  

Cuprous  Hydroxide 

CuOH   .    .  . 

Cuprous  Oxide  

Cu2O  

Cuprous  Sulfide               

Cu2S  

Cuprous  Sulfocyanate 

CuCNS 

(Cyanide  Radical)  

CN  

Cyano  gen 

C2N2.  .    . 

Dextrose,  Cryst  
Dimethylglyoxime  . 

L/6Hi2Oe  •  H2O  

(CH3)2C2(NOH)2... 
Er2O3 

Erbium  Oxide 

(Ethyl  Radical)    

Ethyl  Acetate 

Ethyl  Alcohol  

QjHsOH  

Ferric  (Ammonium)  Alum  
Ferric  Chloride,  Anhyd.  .  . 

Fe2(NH4)2(S04)4- 
24H2O  

FeCl3  

Ferric  Chloride  Cryst 

FeCl3-6H2O 

Ferric  Ferrocyanide  

Fe4[Fe(CN)6l3  

Ferric  Hydroxide 

Fe(OH)3  
Fe(NO3)3  

Ferric  Nitrate,  Anhyd  

Ferric  Nitrate,  Cryst  

Fe(N03)3-9H20.... 
FezOs 

Ferric  Oxide 

Ferric  Oxide,  Hydrated  
Ferric  Phosphate,  Anhyd 

FeaOs-HzO  

FePO4  

Ferric  Potassium  Alum    (See  Poi 
Ferric  Sulfate,  Anhyd  

bassium   Ferric   Aim 
Fe2(SO4)3  

Ferric  Sulfate  Cryst 

Fe2(SO4)3-9H2O.  ... 
FejzSa  

Ferric  Sulfide  *  
Ferroso-f  erric  Oxide                  .  .  . 

Fe3O4 

Ferroso-f  erric  Sulfide  

Fe3S4  

Ferrous  Acetate,  Anhyd 

Fe(C2H302)2  
Fe(C2H302)2-4H20.. 

Fe(NH4)2(S04)2- 
6H2O 

Ferrous  Acetate  Cryst 

Ferrous  Ammonium  Sulfate  
Ferrous  Carbonate   

FeCO3  

Ferrous  Chloride  Anhyd 

FeCl2 

Ferrous  Chloride,  Cryst  
Ferrous  Ferricyanide 

FeCl2-4H2O  

Fe<[Fe(CN)6]2  

*  See  also  Iron  Sul-fide 


TABLES 
TABLE  II— MOLECULAR  WEIGHTS 


595 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Ferrous  Hydroxide.  .  .  . 

Fe(OH)2 

89.86 
71.84 
151.90 
278.01 
87.90 
142.3 
30.021 
96.057 

180.126 
92.079 

34.016 
34.08 
17.008 
63.04 
174.92 
158.92 
162.38 
333.84 
233.30 

119.96 
647.36 

360.252 
326.0 
685.60 

325.27 
608.51 
1422.20 
379.32 
347.17 
899.52 
267.21 
775.64 
278.12 

1.95357 
1.85637 
2.18156 
2.44406 
1.94399 
2  .  15320 
1.47743 
1.98253 

2.25557 
1.96417 

1.53168 
1.53250 
1.23065 
1.79962 
2.24284 
2.20118 
2.21054 
2.52354 
2.36791 

2.07904 
2.81115 

2.55660 
2  .  51322 
2.83607 

2.51224 
2.78427 
3.15296 
2.57900 
2.54054 
2.95401 
2.42686 
2.88966 
2.44423 

Ferrous  Oxide  

FeO:  

Ferrous  Sulf  ate,  Anhyd  
Ferrous  Sulfate,  Cryst 

FeSO4 

FeSO4-7H2O  
FeS  

Ferrous  Sulfide  

(Fluosilicate  Radical)  

SiF6 

Formaldehyde 

HCHO 

Furfural  

C4H3O-CHO.. 

Fusel  Oil    (See  Amyl  Alcohol) 
Galactose 

C«H,oO«. 

Glauber  Salts     (See  Sodium  Sulfate,  Cryst.) 
Glycerol  |C3H5(OH)3.  .  
Gold  Chloride    (See  Auric  Chloride) 
Gypsum     (See  Calcium  Sulfate,  Cryst.) 
Hydrogen  Peroxide  HoOo  

Hydrogen  Sulfide  

H2S... 

(Hydroxyl  Radical) 

HO 

(Hypophosphate  Radical)  
(lodate  Radical)  

PO2  

IO3 

Iodine  Dioxide  

IO2 

Iodine  Monochloride  

IC1  

Iodine  Pentoxide  

I2O5 

Iodine  Trichloride 

IC13 

Iron  Alum  (See  Ferric  Ammoniu 
Iron  Di-sulfide  

tn  Alum)  * 
FeS2 

Iron  Sulfide  

Fe7S8  
roso-ferric  Oxide) 
Ci2H22Oii-H2O 

Iron  Oxide,  Magnetic     (See  Fen 
Lactose,  Cryst  

Lanthanum  Oxide 

LaizOs 

Lead,  Red 

Pb3O4 

Lead,  White    (See  Lead  Carbon. 
Lead  Acetate,  Anhyd  

ite,  Hydrated) 
Pb(C2H3O2)2 

Lead  Acetate,  Basic  
Lead  Acetate,  Basic  t  

Pb2(C2H302)3-OH... 
3Pb(C2H3O2)2-2PbO 
Pb(C2H302)2-3H20.. 
PbHAsO4  .. 

Lead  Acetate,  Cryst  

Lead  Acid  Arsenate.  .  .    . 

Lead  Arsenate     .  . 

Pb3(AsO4)3 

Lead  Carbonate  

PbCO3...    . 

Lead  Carbonate,  Hydrated 

2PbCO3-Pb(OH)2... 
PbCL 

Lead  Chloride 

*For  other  compounds  of  iron  see  under  Ferric  and  Ferrous. 


t  Home's  Reagent. 


596 


TECHNICAL  METHODS  OF  ANALYSIS 
TABLE  II— MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Lead  Chromate   

PbCrO4 

323  2 

2  50947 

Lead  Chromate,  Basic  

PbCrO4-PbO    .  . 

546  4 

2  73751 

Lead  Cyanide  

Pb(CN)2 

259  23 

2  41368 

Lead  Hydroxide 

Pb(OH)2 

241  22 

2  32842 

Lead  Iodide  

PbI2 

461  04 

2  66374 

Lead  Molybdate 

PbMoO4 

367  2 

2  56490 

Lead  Monoxide  

PbO.    . 

223  20 

2  34869 

Lead  Nitrate  

Pb(NO3)2 

331  22 

2  52012 

Lead  Oleate  

Pb(Ci8H33O2)2 

769  21 

2  88644 

Lead  Peroxide  

PbO2 

239  20 

2  37876 

Lead  Stearate 

Pb(Ci8H,fiO2)2 

773  94 

2  88870 

LeadSulfate  

PbS04 

303  26 

2  48181 

Lead  Sulfate  Basic 

PbSO4  •  PbO 

526  46 

2  72137 

LeadSulfide  

PbS 

239  26 

2  37887 

Lead  Tungstate 

pbWO4 

455  2 

2  65820 

Levulose  

C6Hi2O6 

180  126 

2  25557 

Lime  (See  Calcium  Oxide) 
Litharge     (See  Lead  Monoxide) 
Lithium  Acetate,  Anhyd  .... 

LiC2H3O2 

65  97 

1  81935 

Lithium  Acetate,  Cryst  

LiC2H3O2-2H2O    .  . 

102  01 

2  00864 

Lithium  Bromide  

LiBr 

86  86 

1  93882 

Lithium  Carbonate 

LioCO3 

73  89 

1  86859 

Lithium  Chloride  

LiCl 

42  40 

1  62737 

Lithium  Hydroxide 

LiOH 

23  95 

1  37931 

Lithium  Nitrate,  Anhyd  

LiNO3 

68  95 

1  83853 

Lithium  Nitrate,  Cryst  
Lithium  Oxide  

LiNO3-3H2O  
Li2O         .    . 

123.00 

29  88 

2.08991 
1  46538 

Lithium  Phosphate,  Anhyd  
Lithium  Phosphate,  Cryst  
Lithium  Sulfate,  Anhyd  

Li3P04  
Li3P04-H20  
Li2SO4 

115.86 
133.88 
109  94 

2.06393 
2.12672 
2  04116 

Lithium  Sulfate,  Cryst  

Li2SO4-H2O  

127  96 

2  10707 

Magnesia  (See  Magnesium  Oxide) 
Magnesium  Acetate,  Anhyd  .... 
Magnesium  Acetate,  Cryst  
Magnesium  Acid  Sulfite 

Mg(C2H302)2  
Mg(C2H302)2-4H20. 
MgH2(SO3)2 

142.39 
214.45 
186  46 

2  .  15348 
2.33133 
2  26059 

Magnesium  Ammonium  Chloride 

MgCl2-NH4Cl- 
6H2O 

256  84 

2  40966 

Magnesium    Ammonium    Phos- 
phate, Anhyd  

MgNH4PO4 

137  40 

2  13799 

.  Magnesium    Ammonium    Phos- 
phate, Cryst  

MgNH4PO4-6H2O.  . 

245  .  50 

2.39005 

TABLES 
TABLE  II — MOLECULAR  WEIGHTS 


597 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Magnesium  Ammonium  Sulfate. 

Mg(NH4)2(S04)2- 
6H2O 

360  62 

2  55705 

Magnesium  Bicarbonate 

MgH2(CO3)2 

146  35 

2  16539 

Magnesium  Bisulfite  (Meta-).  .  .  . 

MgS2O6 

168  44 

2  22644 

Magnesium  Carbonate 

MgCO3 

84  33 

1  92598 

Magnesium  Carbonate,  Basic  .  .  . 

Mg(OH)2.4MgC03- 
5H2O 

485  74 

2  68641 

Magnesium  Chloride,  Anhyd.  .  .  . 

MgCl2  

95  24 

1  97882 

Magnesium  Chloride,  Cryst  
Magnesium  Hydroxide  
Magnesium  Nitrate,  Anhyd  

MgCl2-6H2O  
Mg(OH)2  
Mg(NO3)2  

203.34 
58.34 
148  34 

2.30822 
1.76597 
2  17126 

Magnesium  Nitrate,  Cryst  
Magnesium  Oxide 

Mg(NO3)2-6H2O.... 
MgO 

256.43 
40  32 

2.40897 
1  60552 

Magnesium  Phosphate,  Anhyd.  . 

Mg3(PO4)2  

263  04 

2  42002 

Magnesium  Phosphate,  Cryst.  .  . 
Magnesium  Pyroarsenate  
Magnesium  Pyrophosphate  

Mg3(PO4)2-4H2O..  . 
Mg2As2O7  
Mg2P2O7  

335.10 
310.56 

222  72 

2.52517 
2.49214 
2  34776 

Magnesium  Silicate  (Meta-)  .... 

MgSiO3           

100  6 

2  00260 

Magnesium  Silicate  (Ortho-) 

MgSiO4 

116  6 

2  06670 

Magnesium  Sulfate,  Anhyd  
Magnesium  Sulfate,  Cryst  

MgS04  
MgSO4-7H2O  

120.38 
246  49 

2.08056 
2  39180 

Magnesium  Sulfite,  Anhyd 

MgSO3 

104  38 

2  01862 

Magnesium  Sulfite  Cryst 

MgSO3-6H2O 

212  48 

2  32732 

Maltose,  Cryst       

C12H22On-H2O  

360  252 

2  55660 

Manganese  Carbonate 

MnCO3 

114  94 

2  06047 

Manganese  Chloride,  Anhyd.  .  .  , 

MnCl2  

125  85 

2  09986 

Manganese  Chloride,  Cryst  

MnCl2-4H2O  

197  91 

2  29647 

Manganese  Dioxide  

MnO2         ... 

86  93 

1  93917 

Manganese  Heptoxide 

Mn2O7 

221  86 

2  34608 

IVlanganese  Hydroxide 

Mn(OH)2 

88  95 

1  94915 

Manganese  Nitrate,  Anhyd  

Mn(NO3)2  . 

178  95 

2  25273 

Manganese  Nitrate,  Cryst   . 

Mn(NO3)2-6H2O 

287  04 

2  45794 

Manganese  Pyrophosphate  

Mn2P2O7  

283  94 

2  45323 

Manganese  Silicate  

MnSiO3  

131  2 

2  11793 

Manganese  Sulfate,  Anhyd  

MnSO4 

150  99 

2  17895 

Manganese  Sulfate,  Cryst  

MnSO4-4H2O  

223.05 

2  34840 

Manganese  Sulfide 

MnS 

86  99 

1  93947 

Manganese  Trioxide  

MnO3.    .    . 

102  93 

2  01255 

Magnanic  Oxide       .... 

Mn2O3 

157  86 

2  19827 

Mangano-manganic  Oxide  

Mn3O4  

228  79 

2  35944 

Manganous  Oxide  

MnO.  . 

70  93 

1  85083 

598 


TECHNICAL  METHODS  OF  ANALYSIS 


TABLE  II — MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Menthol 

Ci0Hi9OH        

156  210 

2  19371 

Menthyl  Acetate                    .... 

198.236 

2.29718 

Mercuric  Bromide 

HgBr2   

360  4 

2.55678 

IVlercuric  Chloride 

HgCl2 

271  5 

2  43377 

Mercuric  Cyanide 

Hg(CN)2  

252.6 

2.40243 

Mercuric  Hydroxide  
Mercuric  Iodide 

Hg(OH),  
HgI2  

234.6 
454.4 

2.37033 
2.65744 

Mercuric  Nitrate,  Anhyd  
Mercuric  Nitrate,  Cryst  
Mercuric  Oxide 

Hg(N03)2  
Hg(N03)2-H20  
HgO 

324,6 
342.6 
216.6 

2.51135 
2.53479 
2.33566 

Mercuric  Sulfate  

HgSO4  

296.7 

2.46232 

Mercuric  Sulfide 

HgS 

232.7 

2.36680 

Mercurous  Chloride    

Hg2Cl2  

472.1 

2.67403 

Mercury  Fulminate 

HgC2N2O2  

284.6 

2.45423 

Methane   

CH4  

16.037 

1.20512 

(Methyl  Radical) 

CH3   

15.029 

1  .  17693 

Methyl  Acetate  

CH3C2H3O2  

74.063 

1.86960 

Methyl  Alcohol 

CH3OH  

32.037 

1  .  50565 

Methvl  Salicvlate..  . 

CH.C7H.O.,.. 

152.104 

2.18214 

Microcosmic  Salt     (See  Ammoni 
Cryst.) 
Minium  (See  Lead,  Red) 
(Molybdate  Radical)  .  . 

um  Sodium  Hydrog 
MoO4       

3n    Phosph 

160.0 
128.0 
240.0 
160.1 
144.0 
336.6 
291.20 
118.69 
129.60 
237.70 
110.71 
182.77 
288.86 
182.69 
290.79 
74.68 
154.74 
90.74 
109.70 

ate, 

2.20412 
2  .  10721 
2.38021 
2.20439 
2.15836 
2.52711 
2  .  46419 
2.07441 
2.11261 
2.37603 
2.04419 
2.26191 
2.46069 
2.26172 
2.46358 
1.87320 
2.18960 
1.95780 
2.04021 

]Vlolybdic  Dioxide 

MoO2 

Molybdic  Oxide                    ... 

Mo2O3  

Molybdic  Sulfide 

MoS2 

Molybdic  Trioxide     

MoO3  

Neodymium  Oxide 

Nd2O3 

Nickel  Ammonium  Chloride  .... 
Nickel  Carbonate 

NiCl2-NH4Cl-6H2O 
NiCO3  

Nickel  Chloride  Anhyd 

NiCl2 

Nickel  Chloride,  Cryst         .    ... 

NiCl2-6H2O  
Ni(CN)2  
Ni(CN)2-4H2O  
NiC8H14N4O4... 

Nickel  Cyanide,  Anhyd  
Nickel  Cyanide,  Cryst  

Nickel  Glyoxime 

Nickel  Nitrate  Anhyd 

Ni(NO3)2 

Nickel  Nitrate,  Cryst  
Nickel  Oxide  

Ni(NO3)2-6H2O.  .  .. 
NiO  

Nickel  Sulfate                 

NiSO4  

Nickel  Sulfide 

NiS  

Nickelic  Hydroxide         

Ni(OH)3  

TABLES 
TABLE  II — MOLECULAR  WEIGHTS 


599 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Nickelo-nickelic  Oxide  
Nickelous  Hydroxide  

Ni3O4  

240.04 
92.70 
162.178 
62.008 
30.008 
108.016 
46.008 
76.016 
44.016 

88.010 
48.000 
122.7 

99.46 
118.93 
162.110 
95.04 
174.08 
79.04 

208.34 
142.08 
137.42 
110.08 
337.0 
427.1 
266.1 

mide) 
98.13 
136.17 
120.17 
258.4 
279.1 

332.4 
100  11 
294.2 
78.1 

2.38028 
1.96708 
2.20999 
1.79245 
1  .  47724 
2.03348. 
1.66283 
1.88091 
1.64361 

1.94453 
1.68124 

2.08884 

1.99765 
2.07529 
2.20981 
1.97791 
2.24075 
1.89785 

2.31877 
2.15253 
2.13805 
2.04171 
2.52763 
2.63053 
2.42504 

1.99180 
2.13408 
2.07979 
2.41229 
2.44576 

2.52166 
2.00047 
2.46864 
1.89265 

Ni(OH)2 

Nicotine 

Ci0Hi4N2 

(Nitrate  Radical) 

NO3 

Nitric  Oxide  

NO  

Nitrogen  Pentoxide 

N2O6 

Nitrogen  Tetroxide  

NO2  

Nitrogen  Trioxide  

N2O3  

Nitrous  Oxide 

N2O 

Orpiment   (See  Arsenous  Sulfide) 
(Oxalate  Radical)  

C2O4...    . 

Ozone 

O3 

Palladium  Monoxide  
Paris  Green    (See  Cupric  Aceto- 
(Perchlorate  Radical) 

PdO  

irsenite) 
C1O4 

(Permanganate  Radical)  
Phloroglucinol,  Cryst.  .  . 

MnO4  

C6H3(OH)3.2H2O... 
P04  
P2O7  

(Phosphate  Radical)  
(Phosphate  Radical,  Pyro-)  

(Phosphite  Radical)    

PO3... 

Phosphoric  Anhydride    (See  Pho, 
Phosphorus  Pentachloride  

sphorus  Pentoxide) 
PC16  

Phosphorus  Pentoxide  
Phosphorus  Trichloride  
Phosphorus  Trioxide  

P205  
PC13  
P2O3  

Platinic  Chloride,  Anhyd  
Platinic  Chloride,  Cryst 

PtCU  

PtCl4-5HoO 

Platinous  Chloride 

PtCl2 

Potash  (See  Potassium  Oxide) 
Potash  Alum  (See  Alum)  
Potassium  Silver  Cyanide     (See 
Potassium  Acetate  

Silver  Potassium  Cyj 
KC2H3O2  

Potassium  Acid  Sulf  ate  

KHSO4  

Potassium  Acid  Sulfite  
Potassium  Aluminum  Fluoride... 
Potassium  Aluminum  Silicate  .  .  . 
Potassium     Aluminum     Sulfate 
Potassium  Antimonyl  Tartrate  .  .  . 
Potassium  Bicarbonate  

KHSO3 

K3A1F6  
KAlSisOg  

(See  Alum) 
KSbOC4H4O6^H2O 
KHCO3  

Potassium  Bichromate  

K2Cr2O7  

Potassium  Bifluoride 

KHF2 

600 


TECHNICAL  METHODS  OF  ANALYSIS 


TABLE  II — MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Potassium  Binoxalate  

KHC2O4  

128.12 

2.10762 

Potassium  Bitartrate  

KHC4H4O6  

188  16 

2  27453 

Potassium  Bromide     .  . 

KBr 

119  02 

2  07562 

Potassium  Carbonate  

K2CO3  

138  21 

2  .  14054 

Potassium  Chlorate  

KC1O3  

122  56 

2  08835 

Potassium  Chloride 

KC1 

74  56 

1  87251 

Potassium  Chlorplatinate  .... 

K2PtCl6..  . 

486  2 

2  68681 

Potassium  Chromate 

K2CrO4 

194  2 

2  28825 

Potassium  Chrome  Alum  
Potassium  Cobaltinitrite,  Anhyd. 
Potassium  Cobaltinitrite,  Cryst.. 
Potassium  Cupric  Chloride  
Potassium  Cupric  Sulf  ate  

K2Cr2(SO4)4-24H2O. 
K3Co(NO2)6  
K3Co(NO2)6-HH2O. 
K2CuCl4-2H2O  
K2Cu(SO4)2-6H2O... 

998.8 
452.32 
479.34 
319.64 
441  .  99 

2.99948 
2.65545 
2.68065 
2.50466 
2.64541 

Potassium  Cyanide 

KCN 

65  11 

1  81365 

Potassium  Ferric  Alum  

K2Fe2(SO4)4-24H2O 

1006.50 

3.00282 

Potassium  Ferricyanide  
Potassium  Ferrocyanide,  Anhyd  . 
Potassium  Ferrocyanide,  Cryst  .  . 
Potassium  Fluoride  

K3Fe(CN)6  
K4Fe(CN)6  
K4Fe(CN)6-3H20... 
KF  

329.22 
368.32 
422.37 
58.1 

2.51749 
2.56622 
2.62569 
1.76418 

Potassium  Fluosilicate  ..... 

K2SiF6  

220.5 

2  34341 

Potassium  Hydrosulfide 

KHS 

72  17 

1  85836 

Potassium  Hydroxide  

KOH  

56.11 

1.74904 

Potassium  lodate 

KIO3 

214  02 

2  33045 

Potassium  Iodide.  .  .  .  

KI  

166.02 

2  .  22016 

Potassium  Nitrate 

KNO3 

101.11 

2  00479 

Potassium  Nitrite.  

KNO2  

85.11 

1  .  92998 

Potassium  Oleate           .... 

320  45 

2  .  50576 

Potassium  Oxalate,  Anhyd  

K2C2O4  

166.21 

2  .  22066 

Potassium  Oxalate,  Cryst  
Potassium  Oxide 

K2C2O4-H2O  
K2O 

184.23 
94  20 

2.26536 
1  97405 

Potassium  Perchlorate  

KC1O4  

138.56 

2  .  14164 

Potassium  Permanganate 

KMnO4 

158.03 

2  .  19874 

Potassium  Persulf  ate  

K2S2O8  

270  .  32 

2.43188 

Potassium  Phosphate,  Di-  
Potassium  Phosphate  Mono- 

K2HPO4  
KH2PO4 

174.25 
136  16 

2.24118 
2  .  13405 

Potassium  Phosphate  (Ortho-)  .  .  . 

K3PO4  

212.34 

2  .  32703 

Potassium  Silicate 

K2SiO3   

154.5 

2  .  18893 

Potassium  Silver  Cyanide 

KAg(CN)2 

199  01 

2.29887 

Potassium    Sodium    Carbonate, 
Anhyd     

KNaCO3  

122.11 

2.08676 

TABLES 
TABLE  II — MOLECULAR  WEIGHTS 


601 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Potassium  Sodium  Carbonate, 
Cryst 

KNaCO3-6H2O  
KNaC4H4O6-4H2O.. 
KCisHssOz  
K2SO4 

230.20 
282.22 
322.47 
174.26 
110.26 
200.34 
158.26 
194.29 
97.17 
226.25 
235.26 
335.4 
160.27 
329.8 

261.92 
174.08 
385.8 
296.9 
594.426 

209.3 

186.90 
266.96 
251.4 
183.14 

348.8 
136.2 

143.2 
127.2 
111.2 

2.36211 
2.45059 
2.50849 
2.24120 
2.04242 
2.30177 
2.19937 
2.28845 
1.98753 
2.35459 
2.37155 
2.52556 
2.20485 
2.51825 

2.41817 
2.24075 
2.58636 
2.47261 
2.77410 

2.32077 

2.27161 
2.42645 
2.40037 
2.26279 

2.54258 
2.13418 

2.15594 
2.10449 
2.04610 

Potassium  Sodium  Tartrate  

Potassium  Stearate  

Potassium  Sulfate 

Potassium  Sulfide,  Anhyd  

K2S  

Potassium  Sulfide,  Cryst  
Potassium  Sulfite,  Anhyd  
Potassium  Sulfite  Cryst 

K2S-5H2O  
K2SO3 

K2SO>-2H2O 

Potassium  Sulfocyanate  

KCNS 

Potassium  Tartrate,  Anhyd  
Potassium  Tartrate,  Cryst  
Potassium  Tetrasilicate  .... 

K2C4H406  
K2C4H4O6^H2O.... 
K2Si4O9   .  .  . 

Potassium  Xanthogenate  

KS2COC2H5  

Praseodymium  Oxide  

Pr,O,  . 

Prussian  Blue    (See  Ferric  Ferrocyanide) 
Prussic  Acid     (See  Acid,  Hydrocyanic) 
Pyrites     (See  Iron  Bisulfide) 
Pyrites,  Magnetic    (See  Iron  Sulfide) 
(Pyroarsenate  Radical)                    AsoO^ 

(Pyrophosphate  Radical)  
Radium  Bromide  

P207  
RaBr2 

Radium  Chloride 

RaCl2 

Raffinose,  Cryst  

C18H32OiC-5H2O  
RhCl3  

Realgar  (See  Arsenic  Disulfide) 
Red  Lead  (See  Lead,  Red) 
Rhodium  Chloride  

Rochelle  Salts     (See  Potassium 
Rubidium  Oxide  

Sodium  Tartrate) 
Rb2O 

Rubidium  Sulfate 

Rb2SO4 

Ruthenium  Oxide  

Ru2O3  

Saccharin  

C7H5SO3N 

Sal  Soda  (See  Sodium  Carbonate, 
Salt  (See  Sodium  Chloride) 
Samarium  Oxide  

Decahydrate) 
SaaOa  

Scandium  Oxide  

ScoO3  

Schlippe's  Salt    (See  Sodium  Thi< 
(Selenate  Radical)  
(Selenite  Radical)  

Dantimonate) 
SeQ4  
SeO3  

Selenium  Dioxide  
Silica  (See  Silicon  Dioxide) 

Se02  

602 


TECHNICAL  METHODS  OF  ANALYSIS 


TABLE  II — MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

(Silicate  Radical  Meta-) 

SiO3 

76.3 
92.3 
257.2 
40.3 
60.3 
104.3 
187.80 
275.77 
143.34 
331.8 
133.89 
234.80 
169.89 
231.76 
199.01 
311.82 
247.82 
165.95 
540.0 
494.78 

82.03 
136.08 

103.05 

157.10 
916.8 
263.0 

1.88252 
1.96520 
2.41027 
1.60531 
1.78032 
2.01828 
2.26370 
2.44055 
2.15637 
2.52088 
2.12675 
2.37070 
2  .  23017 
2.36504 
2.29887 
2.49391 
2.39414 
2.21998 
2.73239 
2.69441 

1.91397 
2.13380 

2.01305 

2.19618 
2.96227 
2.41996 

(Silicate  Radical,  Ortho-)  

SiO4  

(Silicate  Radical,  Tetra-)  
Silicon  Carbide  

S^Og 

SiC  

Silicon  Dioxide 

SiO2  

SiF4  

Silver  Bromide             

AgBr 

Silver  Carbonate 

Ag2CO3 

Silver  Chloride           

AgCl  . 

Silver  Chromate 

Ag2CrO4 

Silver  Cyanide     

AgCN  

Silver  Iodide 

Ael 

Silver  Nitrate  

AgNO3  

Silver  Oxide 

Ag2O 

Silver  Potassium  Cyanide  
Silver  Sulfate 

AgK(CN)2  

Ag2SO4 

Silver  Sulfide  

Ag2S  

Silver  Sulfocyanate 

AgSCN  

Silver  Thioantimonite  

Ag3SbS3  

Silver  Thioarsenite                      .  . 

Ag<tAsS3  

Soda     (See  Sodium  Oxide) 
Soda  Alum     (See  Sodium  Alum) 
Soda  Ash    (See  Sodium  Carbonai 
Sodium  Acetate,  Anhyd  

;e,  Anhyd.) 
NaC2H3O2  

Sodium  Acetate  Cryst 

NaC2H3O2-3H2O.... 
NaHPO3  

Sodium    Acid    Hypophosphate, 
Anhyd 

Sodium     Acid     Hypophosphate, 
Cryst                         .    .    . 

NaHP03-3H20  

Na2Al2(SO4)4-24H2O 
NaAlSi3Os.. 

Sodium  Alum  

Sodium  Aluminum  Silicate.  .  . 

Sodium    Ammonium    Hydrogen  Phosphate    (See  Ammonium  Sodium 
Hydrogen  Phosphate) 


Sodium  Arsenate,  Di-,  Anhyd. 
Sodium  Arsenate,  Di-,  Cryst.  . 
Sodium  Arsenate,  Tri-,  Anhyd . 
Sodium  Arsenate,  Tri-,  Cryst .  . 

Sodium  Arsenite,  Di- 

Sodium  Arsenite,  Tri- 

Sodium  Benzoate , 

Sodium  Bicarbonate .  . 


Na2HAsO4 

Na2HAsO4-7H2O.. 

Na3AsO4 

Na3AsO4-12H2O... 

Na2HAsO3 

Na3AsO3 

NaC7H5O2 

NaHCO3.. 


185.97 
312.08 
207.96 
424 . 15 
169.97 
191.96 
144.08 
84.01 


2.26944 
2.49426 
2.31798 
2.62752 
2.23037 
2.28321 
2.15860 
1.92433 


TABLES 


603 


TABLE  II— MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Sodium  Bichromate,  Anhyd  

NaaCr-A  

262.0 

2.41830 

Sodium  Bichromate,  Cryst  
Sodium  Binoxalate,  Cryst  .  . 

Na2Cr2O7-2H2O.... 
NaHC2O4-H2O 

298.0 
130  03 

2.47422 
2  11404 

Sodium  Bisulfate 

NaHSO4 

120  07 

2  07943 

Sodium  Bisulfite  

NaHSOs   

104  07 

2.01732 

Sodium  Bisulfite  (Meta-)   .  .  . 

Na2S2O5 

190  12 

2  27903 

Sodium  Bromate 

NaBrOa 

150  92 

2  17875 

Sodium  Bromide,  Anhyd  

NaBr 

102  92 

2.01250 

Sodium  Bromide,  Cryst 

NaBr-2H2O 

138  95 

2  14286 

Sodium  Carbonate,  Anhyd  

Na2CO3  

106.01 

2.02535 

Sodium  Carbonate,  Decahydrate 
Sodium  Carbonate,  Monohydrate 

Na2CO3-lOH2O  
Na2CO3-H2O  

286.17 
124.03 

2.45663 
2.09353 

Sodium  Chlorate  

NaClO3  

106.46 

2.02719 

Sodium  Chloride               

NaCl 

58  46 

1.76686 

Sodium  Chromate  Anhyd 

Na^CrC^ 

162  0 

2  20952 

Sodium  Chromate,  Cryst  

Na2CrO4-lOH2O  .. 

342  2 

2.53428 

Sodium  Citrate,  Anhyd  

Na3C6H507 

258  07 

2  41174 

Sodium  Citrate  Cryst 

2Na3C6H6O7-llH2O 

714  32 

2  85389 

Sodium  Cyanide  

NaCN  

49  01 

1.69028 

Sodium  Fluoride 

NaF 

42  0 

1  62325 

Sodium  Fluosilicate  

Na2SiF6  

188.3 

2.27485 

Sodium  Hydrosulfide,  Anhyd  .  .  . 

NaSH          

56  07 

1.74873 

Sodium  Hydrosulfide,  Cryst 

NaSH-2H«O 

92  10 

1  96426 

Sodium  Hydroxide  

NaOH  

40.01 

1.60217 

Sodium  Hypochlorite         .    .    . 

NaOCl 

74  46 

1.87192 

Sodium  Hypophosphate,  Anhyd. 

Na2PO3  

125.04 

2.09705 

Sodium  Hypophosphate,  Cryst  .  . 

Na2PO3-5H2O  

215.12 

2.33268 

Sodium  Hypophosphite,  Anhyd. 

NaH2PO2  

88  06 

1.94478 

Sodium  Hypophosphite,  Cryst... 
Sodium  Hyposulfite 

NaH2PO2-H2O  
NaHSO2 

106.07 
88  07 

2.02560 
1  94483 

Sodium  lodate  

NaIO3  

197.92 

2.29649 

Sodium  Iodide,  Anhyd  

Nal               .    . 

149  92 

2  .  17586 

Sodium  Iodide,  Cryst  
Sodium  Molybdate,  Anhyd  

NaI-2H2O  
Na2MoO4  

185.95 
206.0 

2.26940 
2.31387 

Sodium  Molybdate,  Cryst  

Na-sMoO^HaO.  .  . 

242.0 

2.38382 

Sodium  Nitrate 

NaNO3 

85  01 

1.92947 

Sodium  Nitrite  

NaNO2  

69.01 

1.83891 

Sodium  Nitroprusside,  Cryst.  .  .  . 

Na2Fe(CN)5NO- 
2H2O 

297  95 

2.47415 

Sodium  Oleate 

NaCi8H33O2 

304  35 

2  48337 

Sodium  Oxalate  

Na2C2O4  

134.01 

2.12713 

604 


TECHNICAL  METHODS  OF  ANALYSIS 


TABLE  II — MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Sodium  Oxide  

Na2O  .  .    .  . 

62.00 
122.46 
78.00 
238.12 
142.05 
358.24 
120.06 
138.07 
164.04 
380.23 
126.05 
216.13 
n   Carbona 
rtrate) 
160.08 
122.3 
303.2 
182.91 
306.37 
142.06 
322.22 
78.06 
240.20 
126.06 
252.17 
81.07 
194.05 
230.08 
201.6 
381.8 
479.58 
158.12 
248.20 
294.0 
330.0 
348.2 
184.0 
472.3 
260.5 
194.7 
150.7 

1.79239 
2.08800 
1.89209 
2.37680 
2.15244 
2.55418 
2.07940 
2.14010 
2.21495 
2.58005 
2.10055 
2.33471 
te) 

2.20433 
2.08743 
2.48173 
2.26223 
2.48625 
2.15247 
2.50816 
1.89243 
2.38057 
2.10058 
2.40170 
1.90886 
2.28792 
2.36188 
2.30449 
2.58184 
2  .  68086 
2.19899 
2.39480 
2.46835 
2.51851 
2.54183 
2.26482 
2.67422 
2.41581 
2.28937 
2.17811 

Sodium  Perchlorate 

NaClO4 

Sodium  Peroxide  

Na2O2  

Sodium  Persulfate 

Na2S2Os  
Na2HPO4  
Na2HPO4-12H2O... 
NaH2PO4  
NaH2PO4-H.,O 

Sodium  Phosphate,  Di-,  Anhyd.. 
Sodium  Phosphate,  Di-,  Cryst.  .  . 
Sodium  Phosphate,  Mono-,  Anh'd 
Sodium  Phosphate,  Mono-,  Cryst 
Sodium  Phosphate,  Tri-,  Anhyd. 
Sodium  Phosphate,  Tri-,  Cryst  .  . 
Sodium  Phosphite,  Di-,  Anhyd  .  . 
Sodium  Phosphite,  Di-,  Cryst  .  .  . 
Sodium  Potassium  Carbonate,  (S 
Sodium  Potassium  Tartrate  (See  ] 
Sodium  Salicylate             

Na3P04  
Na3PO4-12H2O  
Na2HP03  
Na2HPO3-5H2O.... 
ee  Potassium  Sodiur 
Potassium  Sodium  Ta 
NaC7H6O3  .  .  . 

Sodium  Silicate  (Meta-) 

Na2SiO3 

Sodium  Silicate  (Tetra-)  ....'... 

NaaSiiOg  

Sodium  Silver  Cyanide 

NaAg(CN)2 

Sodium  Stearate  

NaCi8H35O2  

Sodium  Sulfate,  Anhyd 

Na2SO4 

Sodium  Sulfate,  Cryst  

Na2SO4-10H2O  
Na2S  '  

Sodium  Sulfide,  Anhyd  
Sodium  Sulfide,  Cryst 

Na2S-9H2O 

Sodium  Sulfite,  Anhvd  

Na2SO3  

Sodium  Sulfite,  Cryst  
Sodium  Sulfocyanate  
Sodium  Tartrate,  Anhyd  
Sodium  Tartrate,  Cryst  
Sodium  Tetraborate,  Anhyd  .... 
Sodium  Tetraborate,  Cryst  

Na2SO3-7H2O 

NaCNS  

Na2C4H406  
Na2C4H4O6-2H2O... 
Na2B4O7.. 

Na2B4O7-10H2O.... 
Na«SbS4-9H2O  

Na2S2O3 

Sodium  Thioantimonate  
Sodium  Thiosulf  ate,  Anhyd  
Sodium  Thiosulfate,  Cryst  
Sodium  Tungstate,  Anhyd  .  .  . 

Na2S2O3-5H2O  
Na2WO4..      .. 

Sodium  Tungstate,  Cryst  

Na2WO4-2H2O  

Sodium  Uranate  

Na2UO4  

Sodium  Vanadate,  Anhyd  
Sodium  Vanadate,  Cryst  
Stannic  Chloride 

Na3VO4. 

Na3VO4-16H2O  
SnCl4  

Stannic  Fluoride 

SnF4 

Stannic  Oxide  

SnO2  

TABLES 
TABLE  II— MOLECULAR  WEIGHTS 


605 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Stannic  Phdsphate,  Anhyd 

Sn2P2O9 

443.5 
623.6 
182.8 
189.6 
225.7 
156.7 
152.7 
134.7 
150.8 
147.64 
158.55 
266.65 
203.6 
121.65 
265.78 
211.65 
283.71 
103.63 
183.69 
119.69 
167-.69 
199.75 

342.236 

96.06 
64.06 
135.04 
80.06 
134.98 
118.98 
322.15 
443.0 

159.5 
143.5 
175.5 
366.4 
456.0 

2.64689 
2.79491 
2.26198 
2.27784 
2.35353 
2.19507 
2.18384 
2.12937 
2.17840 
2.16921 
2.20017 
2.42594 
2.30878 
2.08511 
2.42452 
2.32562 
2.45288 
2.01549 
2.26409 
2.07805 
2.22450 
2.30049 

2.53433 

1.98254 
1.80659 
2.13046 
1.90342 
2.13027 
2.07548 
2.50806 
2.64640 

2.20276 
2.15685 
2.24428 
2.56396 
2.65896 

Stannic  Phosphate,  Cryst  

Sn2P2O9-10H2O  
SnS2  

Stannic  Sulfide  

Stannous  Chloride,  Anhyd 

SnCl2 

Stannous  Chloride  Cryst 

SnCl2-2H2O 

Stannous  Fluoride  

SnF2  

Stannous  Hydroxide  

Sn(OH)2    .  . 

Stannous  Oxide 

SnO 

Stannous  Sulfide  

SnS  

Strontium  Carbonate    

SrCO3  

Strontium  Chloride,  Anhyd  
Strontium  Chloride,  Cryst  
Strontium  Chromate  

SrCl2  

SrCl2-6H2O.....  ... 
SrCrO4  

Strontium  Hydroxide,  Anhyd  .  .  . 
Strontium  Hydroxide,  Cryst  .... 
Strontium  Nitrate,  Anhyd  

Sr(OH)2 

Sr(OH)2-8H2O  
Sr(NO3)2  

Strontium  Nitrate,  Cryst  
Strontium  Oxide  

Sr(NO3)2-4H2O 

SrO  

Strontium  Sulfate  

SrSO4  . 

Strontium  Sulfide 

SrS 

Strontium  Sulfite  

SrSO3  

Strontium  Thiosulfate 

SrS2O3  

Sublimed  Lead    (See  Lead  Sulfa 
Sucrose  

,e,  Basic) 

Sugar     (See  Sucrose) 
Sugar  of  Lead  (See  Lead  Acetate, 
Sugar  of  Milk  (See  Lactose) 
(Sulfate  Radical)  

Cryst.) 
SO4  

Sulfur  Dioxide       ... 

SO2.   . 

Sulfur  Monochloride  
Sulfur  Trioxide  

S.C12  "... 

SO3  

Sulfuric  Oxy  chloride  

SO2C12  

Sulf  urous  Oxy  chloride  
Tannin 

SOC12. 

Tantalum  Oxide  

Ta-A  

Tartar  Emetic     (See  Potassium 
Tellurium  Dioxide 

Antimonyl  Tartrate) 
TeO2 

Tellurium  Monoxide  
Tellurium  Trioxide  
Terbium  Oxide  ... 

TeO  
TeO3  
Tr^Os. 

Thallic  Oxide 

T1203 

606 


TECHNICAL  METHODS  OF  ANALYSIS 


TABLE  II— MOLECULAR  WEIGHTS 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Thallous  Oxide       

T12O  

424.0   ' 
180.131 
480.18 
696.37 
264.15 

119.0 
80.1 
124.1 
96.1 
384.4 
189.9 
92.099 
216.0 
248.1 
232.0 
280.2 

270.2 

286.2 
650.5 
714.5 
842.6 
424.3 
341.1 
134.0 
422.2 
182.0 
166.0 
150.0 
137.9 
326.1 
152.104 
18.016 

106.120 
150.105 
395.0 
226.66 

2.62737 
2.25558 
2.68140 
2.84284 
2.42185 

2.07555 
1.90363 
2.09377 
1  .  98272 
2.58478 
2.27852 
1.96426 
2.33445 
2.39463 
2.36549 
2.44747 

2.43169 
2.45667 
2.81325 
2.85400 
2.92562 
2.62767 
2.53288 
2.12710 
2.62552 
2.26007 
2.22011 
2.17609 
2  .  13956 
2.51335 
2.18214 
1.25565 

2.02580 
2.17639 
2.59660 
2.35537 

Theobromiiie                 . 

C7H8N4O2 

Thorium  Nitrate,  Anhyd  

Th(NO3)4  

Thorium  Nitrate,  Cryst  
Thorium  Oxide     

Th(NO3)4-12H2O... 
ThO2  

Tin  Salt  (See  Stannous  Chloride, 
Titanium  Dichloride  

Cryst.)* 
TiCl2  

Titanium  Dioxide 

TiO2 

Titanium  Fluoride  

TiF4  

Titanium  Peroxide       .    . 

TiO3 

Titanium  Sulfate  

Ti2(SO4)3  

Titanium  Tetrachloride  

TiCl4   

Oe.H.5  °  vyH.3  
WO2  

Tungsten  Dioxide       

Tungsten  Disulfide 

WS2 

Tungsten  Trioxide  

WO3  

Tungsten  Trisulfide 

WS3               

Turnbull's  Blue      (See  Ferrous 
Uranium  Dioxide       

Ferricyanide) 
UO2   

Uranium  Trioxide 

UO3 

(Urano-phosphate  Radical)  
(Urano-phosphate  Radical) 

U2P2O7  

U2P2On               

Uranoso-uranic  Oxide  
Uranyl  Acetate  Cryst   ...    . 

U308  
U02(C2H302)2-2H20 
UO2C12  

Uranyl  Chloride  

Vanadium  Dioxide         

V2O2  

Vanadium  Oxysulfate 

V202(S04)3  
V206  
V2O4 

Vanadium  Pentoxide  
Vanadium  Tetroxide 

Vanadium  Trioxide  
Vanadyl  Chloride                     .    . 

V203  
VOC12   

Vanadyl  Sulfate  Di- 

V2O2(SO4)2 

Vanillin                                   

C8H8O3  

Water 

H2O           

Water  Glass     (See  Sodium  Sili< 
White  Lead    (See  Lead  Carbonal 
Xylene  
Xylose                 .          

3ate,  Tetra-) 
:e,  Hydrated) 
C6H4(CH3)2  
CsHioOe  

Ytterbium  Oxide 

Yb2O3 

Yttrium  Oxide 

Yt2O3 

*  For  other  salts  of  Tin  see  under  Stannic  and  Stannous, 


TABLES 
TABLE  II — MOLECULAR  WEIGHTS 


607 


Name 

Formula 

Molecular 
Weight 

Logarithm 

Zinc  Ammonium  Phosphate  
Zinc  Carbonate  

ZnNH4PO4  
ZnCO3 

178.45 
125  38 

2.25152 
2  09823 

Zinc  Chloride 

ZnCl2 

136  29 

2  13447 

Zinc  Ferrocyanide,  Anhyd  

Zn2Fe(CN)6 

342  66 

2  53486 

Zinc  Ferrocyanide,  Cryst. 

Zn2Fe(CN)6-3H2O 

396  71 

2  59847 

Zinc  Hydroxide 

Zn(OH)2 

99  39 

1    QQ7^4 

Zinc  Oxide  

ZnO  

81  37 

1  91046 

Zinc  Pyrophosphate  

Zn2P2O7 

304  82 

2  48404 

Zinc  Sulfate,  Anhyd 

ZnSO4 

161  43 

2  20798 

Zinc  Sulfate,  Cryst  

ZnSO4'7H2O 

287  54 

2  45870 

Zinc  Sulfide  

ZnS 

97  43 

1  98869 

Zirconium  Oxide  

ZrO2 

122  6 

2  08849 

608 


TECHNICAL  METHODS  OF  ANALYSIS 

TABLE  III 

ANALYTICAL  FACTORS 


Wanted 

Found 

Factor 

Logarithm 

Ag 

AgCl 

0  7526 

9  87656 

AgCl  

BaCl2  

1.3764 

0.13874 

CaCl2  
KC1 

2.5830 
1  9225 

0.41212 
0  28386 

MgCl2  
NaCl 

3.0101 
2  4520 

0.47858 
0.38952 

AgNOs,    

ACT    . 

1.5748 

0.19722 

AgCl                  

1  .  1852 

0.07379 

Al       

A12O3  

0.5303 

9.72452 

A1(OH)3  
A1203  
A12(S04)3  
A12(SO4)3-18H2O 

A1203  
A12(S04)3  
A1203  
A12O3 

1.5284 
0.2985 
3.3503 
6.5235 

0.18424 
9.47494 
0.52508 
0.81448 

As  •  

As2O3  

0.7575 

9.87938 

As2O3 

As.  .                   

1.3202 

0.12063 

Cu3(AsO3)2-2As2O3- 
Cu(C2H3O2)2  

0.5855 

9.76753 

As2O5 

Pb3(AsO4)2 

0  2556 

9.40756 

PbHAsO4  

0.3311 

9.51996 

B 

B2O3  

0.3123 

9.49457 

BaCO3 

BaSO4 

0  8456 

9  92716 

Ba,Cl2                ... 

AgCl.. 

0.7265 

9.86124 

BaSO4 

0  8923 

9.95051 

BaO           

BaSO4  

0.6570 

9.81757 

Ba3(PO4)2 

BaSO4  

0.8599 

9.93445 

Mg2P2O7  

2.7038 

0.43198 

P2O6  

4.2384 

0.62720 

BaSO4 

Ba3(TO4)2 

1  1630 

0.06558 

c 

CO2  

0.2728 

9.43584 

CO2 

CaCO3                 .    . 

0.4397 

9.64316 

CaO 

0  7848 

9.89476 

MgO  

1.0914 

0.03798 

Na2CO3 

0  4151 

9.61815 

Pb(OH)2-2PbCO3  
SiO2         .     . 

0.1135 
0.7298 

9.05500 
9.86320 

Ca                      

CaSO4  

0.2944 

9.46894 

CaCO3 

CO2     

2.2743 

0.35685 

CaO  

1.7849 

0.25161 

CaCl2 

AgCl  

0.3872 

9.58794 

TABLES 
TABLE  III — ANALYTICAL  FACTORS 


609 


Wanted 

Found 

Factor 

Logarithm 

CaClo 

CaO                 .        ... 

1  9795 

0  .  29656 

Cl 

1  5650 

0  19451 

CaO  

CO2  

1.2742 

0.10524 

Ca                      .... 

1  .  3993 

0.14591 

CaCO3 

0  5603 

9  74842 

CaCl2  

0.5052 

9.70346 

CaS04  
CaSO4-2H2O 

0.4119 
0  3257 

9.61479 
9.51282 

Ca(OH)o 

CaO 

1  3214 

0  12103 

Ca  Oleate  

CaO   

10.750 

1.03141 

Oleic  Acid               .    ... 

1  0674 

0.02832 

Ca3(PO4)2  

P,O5  

2.1840 

0.33925 

CaSO4       

BaSO4  

0.5832 

9.76582 

CaO                 

2  4279 

0.38523 

SO. 

1  7004 

0  23055 

CaSO4-2H2O  

BaSO4  

0.7375 

9.86776 

CaO           

3  0704 

0.48720 

CaSO4 

1  2646 

0  10195 

SO3  

2.1504 

0.33252 

CaS2O6 

CaO         

3.2850 

0.51654 

SO2 

1  4376 

0  .  15764 

Casein 

N 

6  38 

0  80482 

Cd 

CdSO4        

0.5392 

9.73175 

Cl 

AgCl                      

0  2474 

9  39340 

NH4C1 

0  6628 

9  82138 

NaCl  

0.6066 

9.78290 

ZnCl2   

0  5204 

9.71634 

Cr2Os 

PbCrO4 

0  2352 

9  37144 

Cu           

CuO  

0.7989 

9.90249 

CuO 

Cu  '.  

1.2517 

0.09750 

Cu3(AsO3)2-2As2O3- 
Cu(C2H3O2)2 

0  3139 

9  49679 

Fat  

CaSoap  

0.94 

9.97313 

KSoap  
Na  Soap            

0.88 
0  93 

9.94448 
9  96848 

Pb  Soap 

0  74 

9  86923 

Fatty  Anhydride  

Fattv  Acid  

0.9673 

9.98556 

Fe 

Fe(NH4)2(SO4)2-6H2O... 

0  1424 

9.15351 

Fe2O3 

0  6994 

9  84473 

FeCO3 

Fe2O3 

1  4510 

0  16167 

Fe(NH4)2(SO4)2-6H2O... 

Fe2O3  

4.9115 

0.69122 

610 


TECHNICAL  METHODS  OF  ANALYSIS 
TABLE  III— ANALYTICAL  FACTORS 


Wanted 

Found 

Factor 

Logarithm 

Fe2O3       

Fe  -  

1.4298 

0.15528 

Fe(NH4)2(S04)2-6H20... 
P2O5 

0.2036 
1  1239 

9.30878 
0  05073 

FeSO4 

Fe2O3  

1.9026 

0  27935 

Glue 

N 

5  60 

0  74819 

Glycerol              

K2Cr2O7  

0.1341 

9.12743 

H 

H2O 

0  1119 

9  04883 

HC2H3O2           

Cu3(AsO3)2-2As2O3- 

HCO2H         

Cu(C2H302)2  
HgCl2  

0.1184 
0.09748 

9.07335 

8.98892 

HC1 

AgCl           

0  2544 

9  40552 

H2O 

A1(OH)3 

0  3460 

9  53908 

Ca(OH)2     

0  2432 

9  38596 

CaSO4 

0  2647 

9  42275 

CaSO4-2H2O  

0  2093 

9.32077 

H2SO4 

BaSO4 

0  4202 

9  62346 

H2O  
SO3 

5.4441 
1  2251 

0.73593 
0  08818 

HgCl2            

HgS.  . 

1  .  1667 

6.06696 

I 

Agl 

0  5405 

9  73280 

K             

K2PtCl6  

0.1608 

9.20629 

K2CO3 

K2O     

1  4671 

0  16646 

KC1  

AgCl  

0.5202 

9.71617 

Cl  

2  .  1026 

0  32276 

K2O 

1  5830 

0  19948 

K2O 

K2PtCl6....  
K2CO3 

0.3067 
0  6816 

9.48671 
9  83353 

KC1  

0.6317 

9.80051 

KOH            .  .     . 

0  8394 

9  92397 

K2PtCl6 

0  1938 

9  28735 

K2SO4  

0  5405 

9  73280 

KoSO* 

BaSO4 

0  7465 

9  87303 

KC1  

1  .  1686 

0.06766 

K2O 

1  8499 

0  26715 

K2PtCl6  

0.3584 

9.55437 

SO3  

2  1766 

0  33778 

Li                  

Li2SO4  

0.1263 

9.10140 

Li2O 

Li2SO4  

0  2718 

9  43425 

Me 

MgCO3 

0  2884 

9  46000 

MeCO3 

Mg2P2O7  
CO2 

0.2184 
1  9164 

9.33925 
0  28249 

MgO  

2.0915 

0.32046 

TABLES 
TABLE  III — ANALYTICAL  FACTORS 


611 


Wanted 

Found 

Factor 

Logarithm 

MgCl2 

AgCl 

0  3322 

9  52140 

Cl  

1.3429 

0.12805 

MgO  

2  3621 

0  37330 

MgO 

MgCl2 

0  4234 

9  62675 

Mg2P2O7  

0.3621 

9.55883 

Mg(OH)2-4MgC03- 
5H2O 

MgS04  
Mg2P2O7 

0.3349 
0  8724 

9.52492 
9  94072 

Mg3(PO4)2  

P2O5  

1.8513 

0  26748 

MgSO4            

MgO 

2  9857 

0  47504 

Mg2P2O7  ,  

1.0810 

0.03383 

SO3  

1  .  5036 

0  17713 

MgS2O5            

MgO 

4  1775 

0  62092 

SO2 

1  3147 

0  11883 

Mn     

Fe  

0.9837 

9  .  99286 

Mn2P2O7.                    .    . 

0  3869 

9  58760 

MnCO3 

Mn3O4 

1  5071 

0  17814 

Mn2P2O7  
Mo 

MnO  
PbMoO4 

2.0016 
0  2614 

0.30137 
9  41731 

N 

C7H  8N4O2  (theobromine) 

0  3111 

9  49290 

NH4C1 

C8H10N4O2(caffeine)  .... 
N               

0.2886 
3  8192 

9.46030 
0  58197 

Na 

NaCl 

0  3934 

9  59483 

Na2O  

0.7419 

9.87035 

Na2SO4     

0  3238 

9  51028 

NazCOa 

CO2 

2  4090 

0  38184 

Na  

2.3046 

0.36259 

NaHCO3  
Na2O     

0.6309 
1  7098 

9.79996 
0  23295 

NaOH 

1  3248 

0  12215 

NaaSO4 

0  7462 

9  87286 

NaCl  

AgCl  

0.4078 

9.61045 

Cl  

Na 

1.6486 
2  5417 

0.21712 
0  40513 

Na-sO 

1  8858 

0  27549 

NaHCO3  

Na2CO3  

1  .  5849 

0  20000 

NazO  

2  7100 

0  43297 

Na2HPO4  
NaoO 

P206  
BaSO4 

1.9996 
0  2656 

0.30094 
9  42423 

Na 

1  3478 

0  12963 

Na2CO3  
NaCl  :. 

0.5848 
0.5303 

9.76701. 
9  .  72452 

612 


TECHNICAL  METHODS  OF  ANALYSIS 
TABLE  III— ANALYTICAL  FACTORS 


Wanted 

Found 

Factor 

Logarithm 

Na2O  

NaHCO3  .v,i 

0.3690 

9  .  56703 

NaOH   .... 

0  7748 

9  88919 

Na2S 

0  7943 

9  89998 

Na2SO4  

0  4364 

9  63988 

Na2Si4O9 

0  2045 

9  31069 

NaOH        

Na2CO3  

0.7548 

9.87783 

NasO  

1  2906 

0  11079 

Na2S  

AgNOs  

0.2297 

9.36116 

Zn  

1  1941 

0  07705 

Na2SO4 

BaSO4 

0  6086 

9  78433 

Na2CO3  

1  3401 

0  12713 

Na2O 

2  2913 

0  36008 

SO3       

1  7744 

0  24905 

Na2SO4  •  10H2O 

BaSO4 

1  3804 

0  14000 

Na2SiO3 

Na2O       

1.9726 

0.29504 

SiO2 

2  0282 

0  30711 

Na2Si4O9             

Na2O   

4.8903 

0.68934 

SiO2 

1  2570 

0  09934 

Ni  

Ni-glyoxime  

0.2031 

9.30771 

NiO             

0.7858 

9.89531 

o    

Cl  

0.2256 

9  .  35334 

p 

(NH4)2HPO4-12Mo<X.. 

0.01669 

8.22246 

(NH4)3PO4-12MoO3.... 
P2O5  

0,  01654 
0.4370 

8.21854 
9  .  64048 

P2O5 

Mg2P2O7 

0  6379 

9.80475 

(NH4)2HPO4-12MoO3... 
(NH4)3PO4-12MoO3.... 
p 

0.0382 
0.0378 

2  2886 

8.58206 
8.57749 
0  .  35957 

Pb                    

PbO2  

0.8662 

9.93762 

PbO2 

0  8643* 

9.93666 

PbSO4  

0.6833 

9.83461 

PbCO3 

CO2  

6.0724 

0.78336 

PbCrO4         

Pb(OH)2-2PbCO3  
Cr2O3  

0.6890 
4.2526 

9.83822 
0.62866 

PbCO3                     .    .  .  .' 

1.2095 

0.08261 

PbCrO4  

Pb(C2H,O2)2-3H2O  

0.8521 

9.93049 

pbO                

Pb3(AsO4)2  

0.7444 

9.87181 

PbCrO4 

0  6906 

9  83923 

PbHAsO4  

0.6429 

9  .  80814 

PbO2  

0.9331 

9.96993 

*  Empirical  factor  when  deposited  on  anode  by  electrolysis. 


TABLES 
TABLE  III — ANALYTICAL  FACTORS 


613 


Wanted 

Found 

Factor 

Logarithm 

PbO  

Pb3O4  
Pb(OH)2-2PbC03  
PbSO4 

0.9767 
0.8633 
0  7360 

9.98976 
9.93616 
9  86688 

Pb(OH)2          

PbCrO4 

0  7464 

9  87297 

Pb(OH)2-2PbCO3 
(White  Lead)  

Pb(OH)2-2PbCO3  
CO2 

0.3110 

8  813 

9.49276 
0  94512 

PbCrO4  

0  8000 

9  90309 

PbSO4  

0  8526 

9  93075 

PbSO4  

BaSO4 

1  2991 

0  11364 

PbCrO4  

0  9383 

9  97234 

Pb  Stearate  

PbSO4  

2  5521 

0  40690 

Protein  

N  

6  25 

0  79588 

Protein  (in  wheat  prod- 
ucts) 

N 

5  70 

0  75587 

Pt  

NaCl 

1  6695 

0  22259 

PtCl4   . 

NaCl 

2  8823 

0  45974 

Rosin  Anhydride.  ...... 

Pt  
Rosin  Acids 

1.7264 
0  9732 

0.23714 
9  98820 

S  

BaSO4 

0  1373 

9  13767 

Na2S  
Na2S-9H2O. 

0.4107 
0  1335 

9.61352 
9  12548 

Na2S2O3 

0  4055 

9  60799 

SO2 

BaSO4 

0  2744 

9  43838 

CaS2O5  

0  6956 

9  84236 

MgS2O5 

0  7606 

9  88116 

SO,  

A12(SO4)3  
BaSO4  

0.7015 
0  3430 

9.84603 
9  53529 

Fe2O3(from  FeSO4) 

1  0028 

0  00121 

FeSO4 

0  5271 

9  72189 

Na2SO4  

0  5636 

9  75097 

Sb2O4  

Sb  

1  2662 

0  10250 

Si  

SiO2  .... 

0  4693 

9  67145 

SiO2 

Na2Si4O9 

0  7955 

9  90064 

Sn 

SnO2 

0  7877 

9  89636 

SnO2  

Sn  

1  2696 

0  10366 

Ti  

TiO2  

0  6005 

9  77851 

V  ..      . 

Fe 

0  9133 

9  96061 

W 

WO3 

0  7931 

9  89933 

Zn.. 

( 

K2Cr2O7  
ZnNH4PO4  

0.6666 
0.3663 

9.82387 
9.56384 

614 


TECHNICAL  METHODS  OF  ANALYSIS 
TABLE  III— ANALYTICAL  FACTORS 


Wanted 

Found 

Factor 

Logarithm 

Zn  

ZnO  

0.8034 

9  .  90493 

Zn2P2O7 

0  4289 

9  63236 

ZnCl2  

Zn2P2O7  

0.8943 

9.95148 

ZnO  

Zn2P2O7  
ZnS 

0.5339 
0  8532 

9  .  72746 
9  92179 

ZnS 

ZnO             

1  .  1974 

0  .  07824 

TABLES 


615 


TABLE  IV 

VOLUMETRIC  SOLUTIONS 
1  cc.  of  1.0  N  HC1  is  equivalent  to: 


Substance 

Gram 

Logarithm 

Amyl  Acetate,  t  C5HiiC2H3O2  

0  13015 

9  11445  —  10 

BaCO3  f                

0  09869 

8  99427 

Ba(OH)2 

0  08570 

8  93298 

Bornyl  Acetate,  %  Ci0H17C2H3O2  
Ca(Ci8H33O2)2  

0.19622 
0  3014 

9.29274 
9  47914 

Ca(Ci8H35O2)2 

0  3034 

9  48202 

CaCO3  f  

0  05004 

8  69932 

CaO   '. 

0  02804 

8  44778 

Ca(OH)2 

0  03705 

8  56879 

Casein  (NX6.38)  ,. 
Ethyl  Acetate,!  C2H5C2H3O,  . 

0.08937 
0  08808 

8.95119 
8  94488 

Glue  (NX  5  60) 

0  07844 

8  89454 

HC1  

0  03647 

8  56194 

0  3205 

9  50583 

0  3225 

9  50853 

K2CO3  f 

0  06910 

8  83948 

KHCO3  f  .      . 

0  10011 

9  00047 

KNO3 

0  10111 

9  00479 

K2O  

0  04710 

8  67302 

KOH  

0  05611 

8  74904 

Menthyl  Acetate,  J  Ci0Hi9C2H3Oo 

0  19824 

9  29719 

Methyl  Acetate,  %  CH3C2H3O2  
MgCO3  1  .  • 

0.07406 
0  04217 

8.86958 
8  62500 

MgO  t 

0  02016 

8  30449 

Na2B4O7  f 

0  1008 

9  00346 

NaoB4O7-  10H2Ot  

0  1909 

9  28081 

NaC2H3O2  

0  08203 

8  91397 

NaC2H3O2-3H2O  

0  13608 

9  13380 

NaCi8H33O2 

0  3044 

q  48^44 

NaCi8Hs6O2 

0  3064 

q  4862Q 

Na2CO3  f  

0  05300 

8  72428 

NaoCO3-H2Ot  

0  06201 

8  79246 

Na2CO3  •  10H2O  f 

0  14308 

Q    l^ZR 

Na2C2O4 

0  13401 

Q  12713 

NaHCO3  f  

0  08401 

8  92433 

t  Methyl  Orange  Indicator. 

J  By  Saponification  with  Caustic  Solution. 


016 


TECHNICAL  METHODS  OF  ANALYSIS 


TABLE  IV — VOLUMETRIC  SOLUTIONS — (1.0  N  HCl — Continued) 
1  cc.  of  1.0  N  HCl  is  equivalent  to: 


Substance 

Gram 

Logarithm 

Na2HPO  4*  

0.14205 

9.15244—10 

Na2HPO4'-12H2O*. 

0  3582 

9  55413 

Na2O  

0.03100 

8.49136 

NaOH  

0.04001 

8.60217 

Na3PO4  * 

0  16404 

9  21495 

Na3PO4t  

0.08202 

8.91392 

Na2S  * 

0  07806 

8  89243 

Na2Si4O9 

0  1516 

9  18070 

N 

0  014008 

8  14638 

NH3  

0.01703 

8.23121 

NH4              .      . 

0  01804 

8  25624 

NH4Ci8H33O2  

0.2994 

9.47625 

NH4C1     

0.05350 

8.72835 

(NH4)2O 

0  02604 

8  41564 

NH4OH  

0.03505 

8.54469 

Nicotine,  CioHi4N2  

0.01622 

8.21005 

Protein  (NX  6.  25)  

0.08755 

8.94226 

Protein  (NX  5  70) 

0  07985 

8  90227 

Prussian  Blue,  Fe4[Fe(CN)6]3  

0.04773 

8.67879 

Tallow  Oil  §       

0  2877 

9  .  45894 

Wool  Greaself  

0.5501 

9.74044 

1  cc.  of  0.5  N  HCl  is  equivalent  to: 


Amyl  Acetate,t  C5HnC2H3O2  
BaCO3  f          

0.06507 
0  04935 

8.81338-10 
8.69329 

Ba(OH)2  

0.04285 

8.63195 

Bornyl  Acetate,  J  Ci0HnC2H3O2  

Ca(Ci8H33O2)2 

0.09811 
0  1507 

8.99171 
9  17811 

Ca(Ci8H35O2)2  

0.1517 

9.18099 

CaCO3f 

0.02502 

8.39829 

CaO  

0.01402 

8.14675 

Ca(OH)o        

0.01852 

8.26764 

Casein  (NX  6  38) 

0  04469 

8.65021 

Ethyl  Acetate,!  C2H6C2H3O2  

0.04404 

8.64385 

*  Phenolphthalein  Indicator. 

t  Methyl  Orange  Indicator. 

%  By  Saponification  with  Caustic  Solution. 

§  Saponification  Value  195. 

Tf  Saponification  Value  102 . 


TABLES 


617 


TABLE  IV — VOLUMETRIC  SOLUTIONS — (0.5  N  HCl — Continued) 
1  cc.  of  0.5  N  HCl  is  equivalent  to: 


Substance 

Gram 

Logarithm 

Glue  (NX5  60)                                              ... 

0  03922 

8  59351-10 

HCl 

0  018235 

8  26091 

0.1602 

9.20466 

0  1612 

9  20737 

K2CO3  f 

0  03455 

8  53845 

KHCO3  f 

0  05006 

8  69949 

KNO3                                           

0.05055 

8  70372  ' 

K2O 

0  02355 

8  37199 

KOH               

0.028055 

.  8.44801 

Menthyl  Acetate,  J  Ci0H19C2H3O2..  .  
Methyl  Acetate,  J  CH3C2H3O2 

0.09912 
0  03703 

8.99616 
8  56855 

MgCO3  f        

0.02108 

8.32387 

MgOt 

0  01008 

8  00346 

N 

0  007004 

7  84535 

NH3                     

0.008516 

7.93024 

NH4                                                    

0  009020 

7  95521 

NH4Ci8H33O2 

0  1497 

9  17522 

NH4C1   

0.02675 

8.42732 

(NH4)oO                                                 

0  01302 

8  11461 

NH4OH 

0  017524 

8  24363 

Na2B4O7  f              

0.05040 

8.70243 

Na»B4O7  •  10H2O  f                                    

0  09545 

8  97978 

NaC2H3O2 

0  04102 

8  61300 

NaC2H3O2-3H2O.....  
NaCi8H33O2.               .    

0.06804 
0.1522 

8.83276 
9  18241 

NaCi8H35O2 

0  1532 

9  18526 

Na2CO3  f 

0  02650 

8  42325 

Na2CO,-H2Of     

0.03101 

8.49150 

Na2CO3  •  10H2O  f           

0.07154 

8  85455 

Na2C2O4 

0  06701 

8  82614 

NaHCO3  1 

0  04201 

8  62335 

Na»HPO4*  '  

0.07103 

8  .  85144 

Na2HPO4-12H20  *  
Na^O                 .                  

0.1791 
0  "01550 

9.25310 
8  19033 

NaOH 

0  020005 

8  30114 

Na3PO4  * 

0  08202 

8  91392 

Na3PO4  f  

0.04101 

8  61289 

Na2S  *             

0  .  03903 

8  59140 

Na->Si4O9                                                  

0  0758 

8  87967 

*  Phenolphthalein  Indicator, 
t  Methyl  Orange  Indicator. 
J  By  Saponification  with  Caustic  Solution. 


618 


TECHNICAL  METHODS  OF  ANALYSIS 


TABLE  IV— VOLUMETRIC  SOLUTIONS— (0.5  N  HCl— Continued) 
1  cc.  of  0.5  N  HCl  is  equivalent  to: 


Substance 

Gram 

Logarithm 

Nicotine,  CioHi4N2. 

0  08109 

8  90897—10 

Protein  (NX6.25)  

0.04378 

8.64128 

Protein  (N  X5  .  70)  

0  03992 

8  60119 

Prussian  Blue,  Fe4[Fe(CN)6]3  

0.02386 

8.37767 

Tallow  Oil  §  

0  1439 

9  15806 

Wool  Grease  H  . 

0  275 

9  43949 

1  cc.  of  1 .0  N  NaOH  is  equivalent  to: 


Abietic  Acid,*  HC20H29O2  
Acetic  Anhydride,*  (CH3CO)2O 

0.3023 
0  05103 

9.48044-10 
8  70783 

A12(SO4)3.  . 

0  05707 

8  75641 

Amyl  Acetate,  J  C3HuC2H3Oo  

0  13015 

9  11445 

B2(X  *  

0  03490 

8  54283 

B4O7  * 

0  03890 

8  58995 

Benzoic  Acid,*  HC7H5O2 

0  12208 

9  08665 

Bornyl  Acetate,  J  Ci0H17C2H3O2  

0  19622 

9  29274 

Butyric  Acid,  *  HC4H7O2  .  .    . 

0  08808 

8  94488 

C02  *  

0  04400 

8  64345 

Ca(C2H3O2)2  

0  07907 

8  89801 

Ca(Ci8H33O2)2   . 

0  3014 

9  47914 

Ca(Ci8H35O2)2  

0  3034 

9  48202 

Citric  Acid,  Cryst  ,  HoC6H5O7  •  H.O 

0  07004 

8  84535 

Cl 

0  03546 

8  54974 

Ethyl  Acetate,|  C2H6C2H,O2 

0  08808 

8  94488 

Formaldehyde,  HCOH  

0.03002 

8.47741 

Formic  Acid,*  HCO2H  

0  04602 

8  66295 

Glycerol,  ||  C3H5(OH)3 

0  03069 

8  48700 

H3BO-  * 

0  06190 

8  79169 

HBr  

0  08093 

8  90811 

HC2H3O2  * 

0  06004 

8  77844 

H2C2O4*  

0  04501 

8  65331 

H2C2O4-2H2O* 

0  06303 

8  79955 

HCl  

0.03647 

8.56194 

HI  

0.12793 

9.10697 

*  Phenolphthalein  Indicator; 

t  Methyl  Orange  Indicator. 

t  By  Saponification. 

§  Saponification  Value  195. 

f  Saponification  Value  102. 

II  By  Saponification  after  Acetylization. 


TABLES 


619 


TABLE  IV— VOLUMETRIC  SOLUTIONS— (1.0  N  NaOH— Continued) 
1  cc.  of  1.0  N  NaOH  is  equivalent  to: 


Substance 

Gram 

Logarithm 

HNO3 

0  06302 

8  79948  —  10 

H3PO4  *  

0  04903 

8  69046 

H3PO4  f  

0  09806 

8  99149 

H2SO3  * 

0  04104 

8  61321 

H2SO4 

0  04904 

8  69055 

0  3205 

9  50583 

0  3225 

9  50853 

KHCO3 

0  10011 

9  00047 

KHCoO4*  

0  12812 

9  10762 

Lactic  Acid,*  HC3H6O'   . 

0  09006 

8  95453 

Malic  Acid  *  H2C4H4O5 

0  06703 

8  82627 

Menthol,!]  C10H19OH  

0  15621 

9  19371 

Menthyl  Acetate,  |  CioHi9C2H3O2 

0  19824 

9  29719 

Methyl  Acetate,!  CH3C2H3O2  

0.07406 

8  86958 

N  

0  014008 

8  14638 

NO3              

0  06201 

8  79246 

N2O5 

0  05401 

8  73247 

Na2B4O7*  

0  05040 

8  70243 

Na2B4O7  •  10H2O  * 

0  09545 

8  97978 

NaC7H5O2  

0  14408 

9  15860 

NaC7H5O3  

0  16008 

9  20433 

NaC]8H3*O2 

0  3044 

9  48344 

NaCi8H35O2  

0  3064 

9  48629 

NaHCO3  

0  08401 

8  92433 

NaOH 

0  04001 

8  60217 

Oleic  Acid,*  HC18H33O2  

0  2824 

9  45086 

Pb(C2H3O2)9-3H2O  

0  18966 

9  27798 

Salicylic  Acid,*  HC7H6O3   . 

0  13808 

9  14013 

SO2*    

0  03203 

8  50556 

SO3 

0  04003 

8  60239 

SO4  

0  04803 

8  68151 

Stearic  Acid,*  HCi8H36O2 

0  2844 

9  45393 

Tallow  Oil  §  

0.2877 

9  45894 

Tartaric  Acid,  Anhyd.,*  H2C4H4O6  

0  07503 

8  87523 

Tartaric  Acid,  Cryst.,*  H2C4H4O6  •  H2O  
Wool  Grease  If 

0.08404 
0  5501 

8.92449 
9  74044 

*  Phenolphthalein  Indicator, 
t  Methyl  Orange  Indicator. 
J  By  saponification. 
§  Saponification  Value  195 
7  Saponification  Value  102. 
II  By  Saponification  after  Acetylization. 


620  TECHNICAL  METHODS  OF  ANALYSIS 

TABLE  IV — VOLUMETRIC  SOLUTIONS — (Continued) 
1  cc.  of  0.5  N  NaOH  is  equivalent  to: 


Substance 

Gram 

Logarithm 

Abietic  Acid,*  HG>oH29O2 

0  1512 

9  17955     10 

Acetic  Anhydride,*  (CH3CO)2O  

0  025517 

8  40683 

A12(SO4)3                

0  02853 

8  45530 

Amyl  Acetate  J  C5HnC2H3O2 

0  06507 

8  81338 

Benzoic  Acid,*  HC7H5O2  

0  06104 

8  78561 

B->O3  * 

0  01745 

8  24180 

B4O7  *  

0  01945 

8  28892 

Bornyl  Acetate,}  Ci0Hi7C2H3O2  
Butyric  Acid,*  HC4H7O2  

0.09811 
0  04404 

8.99171 
8  64385 

CO2  *         

0  02200 

8  34242 

Ca(C2H3O2)2 

0  3954 

8  59704    ' 

Ca(Ci8H33O2)2  

0  1507 

9  17811 

Ca(Ci8H35O2)2  

0  1517 

9  18099 

Citric  Acid,  Cryst  ,  H3C6H5O7  •  H2O 

0  03502 

8  54432 

Cl  

0.01773 

8  24871 

Ethyl  Acetate,}  C2H5C2H3O2  

0  04404 

8  64385 

Formaldehyde  HCOH 

0  01501 

8  17638 

Formic  Acid,*  HCO2H  

0  02301 

8  36192 

Glycerol,  §C3H5(OH)3 

0  015347 

8  18603 

H3BO3  * 

0  '03095 

8  49066 

HBr            

0  04047 

8  60713 

HC2H3O2  *  

0.03002 

8  47741 

H2C2O4  *    .    ...    . 

0  022507 

8  35232 

H2C2O4-2H2O  * 

0  03151 

8  49845 

HC1  

0  018235 

8  26091 

HI 

0  06397 

8  80598 

HNO3  

0  03151 

8  49845 

H3PO4  * 

0  024515 

8  38943 

H3PO4  f  

0.04903 

8  69046 

H2SO3  *                      

0  02052 

8  31218 

H2SO4 

0  02452 

8  38952 

0  1602 

9  20466 

0  1612 

9  20737 

KHCO3  

0  05006 

8  69949 

KHC2O4*                              .    . 

0  06406 

8  80659 

Lactic  Acid,*  HC3H5O3  
Malic  Acid,*  H2C4H4O5 

0.04503 
0  03352 

8.65350 
8  52530 

*  Phenolphthalein  Indicator. 

t  Methyl  Orange  Indicator. 

t  By  Saponification. 

§  By  Saponification  after  Acetylization. 


TABLES 


621 


TABLE  IV— VOLUMETRIC  SOLUTIONS— (0.5  N  NaOH— Continued) 
1  cc.  of  0.5  N  NaOH  is  equivalent  to: 


Substance 

Gram 

Logarithm 

Menthol  §  d0Hi9OH                               

0.07811 

8  89271-10 

Menthyl  Acetate  {  CioHi9C2H3O2 

0  09912 

8  99616 

Methyl  Acetate,  }  CH3C2H3O2  

0.03703 

8  .  56855 

N                                                            

0.007004 

7  84535 

NO3 

0  03100 

8  49136 

NoO5                       

0.02700 

8.43136 

Na2B4O7  *                                               

0.02520 

8  40140 

Na2B4O7  •  10H2O  * 

0  04773 

8  67879 

NaC7H5Oo     

0.07204 

8.85757 

NaC7H5O3                                            

0.08004 

8  90331 

NaCi8H33O2 

0  1522 

9  18241 

NaCi8H35Oo  

0.1532 

9  .  18526 

NaHCOs                                            

0.04201 

8  62335 

NaOH  

0.020005 

8.30114 

Oleic  Acid,*  HCi8H33O2  

0.1412 

9  14983 

Pb(G>H3O2)o-3H2O                                 .      . 

0.09483 

8  97695 

Salicylic  Acid  *  HC7H5O3 

0  06904 

8  83910 

SO2*   

0.016015 

8  .  20453 

SO3 

0  020015 

8  30136 

SO4     

0.024015 

8.38048 

Stearic  Acid,*  HCi8H35O2  
Tallow  Oil  H 

0.1422 
0  1439 

9.15290 
9  15806 

Tartaric  Acid,  Anhyd  ,*  H2C4H4O6  

0.03752 

8.57426 

Tartaric  Acid,  Cryst.,*  H2C4H4O6-H2O  
Wool  Grease  !| 

.0.04202 
0  2751 

8.62346 
9  43949 

1  c.c.  of  0.1  N  AgNO3  is  equivalent  to: 


Ag  

0.010788 

8.03294  —  10 

AgNO3               

0.016989 

8  23017 

BaCl2 

0  010415 

8  01766 

BaClo-2H2O 

0  012216 

8  08693 

Br     

0.007992 

7  .  90266 

CaCl2     

0  005550 

7  74429 

CdCl2 

0  009166 

7  96218 

CdI2  '.  

0.018312 

8.26274 

*  Phenolphthalein  Indicator. 

J  By  Saponification. 

§  By  Saponification  after  Acetylization. 

I  Saponification  Value  195. 

II  Saponification  Value  102. 


622 


TECHNICAL  METHODS  OF  ANALYSIS 


TABLE  IV — VOLUMETRIC  SOLUTIONS — (0.1  N  AgNOs — Continued) 
1  cc.  of  0.1  N  AgNO3  is  equivalent  to: 


Substance 


Gram 


Logarithm 


Cl 0.003546 

CN* 0.005203 

FeCl2 0.006338 

FeCl3 0.005407 

HBr 0.008093 

HC1 0.003647 

HCN  * ! 0.005404 

HI 0.012793 

I 0.012692 

KBr 0.011902 

KC1 , 0.007456 

KCN  * 0.013022 

KI 0.016602 

K20 0.004710 

KSCN 0.009717 

LiCl 0.004240 

MgCl2 0.004762 

MgCl2-6H2O 0.010167 

NaBr 0.010292 

NaBr-2H20 0.013895 

NaCl 0.005846 

NaCN  * 0.009802 

Nal 0.014992 

NaI-2H2O 0.018595 

Na20 0.003100 

NH4Br 0.009796 

NH4C1. 0.005350 

NHJ 0.014496 

NH4SCN 0.007611 

PbCl2 0.013906 

SrCl2 0.007928 

SrCl2-6H20 0.013333 

Theobromine,  C7H8N4O2 0.018013 

ZnCl2 0.006815 


7.54974- 

7.71625 

7.80195 

7.73296 

7.90811 

7.56194 

7.73272 

8.10697 

8.10353 

8.07562 

7.87251 

8.11468 

8.22016 

7.67302 

7.98753 

7.62737 

7.67779 

8.00719 

8.01250 

8.14286 

7.76686 

7.99131 

8.17586 

8.26940 

7.49136 

7.99105 

7.72835 

8.16125 

7.88144 

8.14320 

7.89916 

8.12493 

8.25558 

7.83347 


-10 


*  Liebig  Method     (See  page  31). 


TABLES 


623 


TABLE  IV — VOLUMETRIC  SOLUTIONS — (Continued) 
1  cc.  of  0.1  N  Iodine  is  equivalent  to: 


Substance 

Gram 

Logarithm 

Acetone   (CH3)oCO 

0  0009677 

6  98574-10 

As  

0.003748 

7.57380 

AsO3  

0  006148 

7.78873 

As2O3             

0  004948 

7  69443 

As2O5 

0  005748 

7  75952 

Br  

0  007992 

7  90266 

CaOCl2  (Bleach)  

0  006350 

7  80277 

Cl 

0  003546 

7  54974 

CrO3 

0  003333 

7  52284 

Cr2O3  

0  002533 

7  40364 

Cu 

0  006357 

7  80325 

CuO  

0.007957 

7.90075 

CuSO4  

0  015963 

8  20311 

CuSO4-5H2O                                      .      . 

0  024971 

8  39744 

Fe'" 

0  005584 

7  74695 

Fe2O3  

0  007984 

7.90222 

HNO2                               ... 

0  002351 

7  37125 

H2S 

0  001704 

7  23147 

H2SO3  

0  004104 

7  61321 

Iodine                  .          

0  012692 

8  10353 

KC1O3 

0  002043 

7  31027 

K2CrO4 

0  006473 

7  81111 

K2Cr2O7         ... 

0  004903 

7  69046 

KMnO4 

0  003161 

7  49982 

KNO2 

0  004256 

7  62900 

Na2CrO4  

0  005400 

7.73239 

Na^Cr-sOr                

0  004367 

7  .  64018 

Na-iCraOr^HijO             

0  004967 

7  69609 

NaNO2 

0  003451 

7  53794 

Na2S  

0.003903 

7.59140 

Na2S-9H2O  
NaeSO3                    

0.012010 
0  006303 

8.07954 
7  79955 

Na2S(X  •  7H«O 

0  012609 

8  10069 

Na2S2O3 

0  015812 

8  19899 

Na2S2O3  -5H..O  

0  024820 

8  39480 

Nag&Os                         

0  004753 

7  67697 

(NH4)2CrO4 

0  005070 

7  70501 

Oxveen.  . 

0.0008000 

6.90309 

624 


TECHNICAL  METHODS  OF  ANALYSIS 


TABLE  IV — VOLUMETRIC  SOLUTIONS — (0.1  N  Iodine — Continued] 
I  cc.  of  0.1  N  Iodine  is  equivalent  to: 


Substance 

Gram 

Logarithm 

PbCrO4                                                    '  . 

0  010773 

8  03234  —  10 

PbO2                 

0.011960 

8  .  07773 

Pb3O4                                           

0.03428 

8  53504 

S 

0  001603 

7  20493 

SO2                              

0.003203 

7  50556 

Sb                                                                     . 

0  006010 

7  77887 

SboOg                         

0.007210 

7  85794 

Sn                                                               .... 

0  005935 

7  77342 

1  cc.  of  0. 1  N  Na2S2O3  is  equivalent  to: 


Acetone   (CH3)2CO                 

0  0009677 

6  98574  —  10 

Br 

0  007992 

7  90266 

CaOCl2  (Bleach)  

0.006350 

7  80277 

Cl 

0  003546 

7  54974 

CrO3         

0.003333 

7  52284 

Cr2O3  

0.002533 

7  .  40364 

Cu  

0.006357 

7  80325 

CuO                                              .      

0  007957 

7  90075 

CuSO4 

0  015963 

8  20311 

CuSO4-5H2O         

0  .  024971 

8  39744 

HNO2 

0  002351 

7  37125 

Iodine       

0.012692 

8  10353 

K2CrO4                                          

0  006473 

7  81111 

K2Cr2O7  

0.004903 

7  69046 

Na2CrO4                

0  005400 

7  73239 

Na2Cr2O7 

0  004367 

7  64018 

Na2Cr2O7-2H2O  

0  .  004967 

7  69609 

NaNO2                    

0  003451 

7  53794 

Na^Os 

0  015812 

8  19899 

Na2S2O3  •  5H2O   

0  .  024820 

8  39480 

(NH4)oCrO4                  

0  005070 

7  70501 

PbCrO4 

0  010773 

8  03234 

PbOo                

0  011960 

8  07773 

Pb3O4 

0  03428 

8  53504 

s 

0  001603 

7  20493 

SO2  

0.003203 

7  50556 

Sb                

0.006010 

7  77887 

SbzOs                      

0  007210 

7  85794 

Sn     

0.005935 

7  77342 

TABLES 


625 


TABLE  IV — VOLUMTERIC  SOLUTIONS — (Continued) 
1  cc.  of  0.1  N  KMnO4  is  equivalent  to: 


Substance 

Gram 

Logarithm 

BaO2  

0  008469 

7  92783  —  10 

BaO2-8H2O 

0  015675 

8  19521 

CaCO3 

0  005004 

7  69932 

CaO  

0  0028035 

7  44770 

CaO2 

0  0036035 

7  55672 

CaSO4  

0  006807 

7  83296 

CaSO4.2H2O  

0  008608 

7  93490 

Fe 

0  005584 

7  74695 

Fe(NH4)2(SO4)2-6HoO  

0  039214 

8  59344 

FeO  

0  007184 

7  85637 

FeoO3 

0  007984 

7  90222 

Fe3O4  

0  007717 

7  88745 

FeSO4       

0  015190 

8  18156 

FeSO4-7H2O 

0  027801 

8  44406 

HCOoH  (Formic  Acid)  

0  002301 

7  36192 

H2C2O4  

0  004501 

7  65331 

H2C2O4-2H2O 

0  006303 

7  79955 

H,O2  

0  003402 

7  53173 

Iodine  

0  012692 

8  10353 

KMnO4 

0  003161 

7  4QQS2 

KNO2  

0  004256 

7  62900 

K2Cr2O7  

0  004903 

7  69046 

K2S2O8 

0  013516 

8  13085 

Mn  

0  0010986 

7  04084 

MnO  

0  0014186 

7  15186 

MnO2  

0  004347 

7  63819 

MoO3  * 

0  0049 

7  6Q020 

Na2CoO4  

0  006701 

7  82614 

NaNO2  

0  003451 

7  53794 

Na2S2O8  

0  011906 

8  07577 

(NH4)2C2O4 

0  006205 

7  70074 

(NH4)2C2O4-H2O  

0  007105 

7  85156 

(NH4)2S2O8  

0  011410 

8  05729 

P  *  .. 

0  000089 

f)  Q4Q3Q 

P2O5  * 

0  000203 

6  ^07^0 

Sb 

0  006010 

7  77SS7 

Sn  

0  005935 

7  77^49 

Tannin,  C14Hi0O9  

0  004157 

7  R1S7S 

*  From  titration  of  yellow  phosphomolybdate  after  reduction     (See  page  25). 


626 


TECHNICAL  METHODS  OF  ANALYSIS 


TABLE  IV — VOLUMETRIC  SOLUTIONS — (Continued) 
1  cc.  of  0. 1  N  K2Cr2O7  is  equivalent  to: 


Substance 

Gram 

Logarithm 

CrO3   

0  .  003333 

7  52284  —  10 

Cr2O3 

0  002533 

7  40364 

Fe"  

0  005584 

7  74695 

FeO 

0  007184 

7  85637 

Fe3O4           '.  

0  .  007717 

7  88745 

FeSO4 

0  015190 

8  18156 

FeSO4-7H2O  

0  027801 

8  44406 

Glycerol   C3H5(OH)3 

0  0006577 

6  81803 

K2Cr2O7  

0  004903 

7  69046 

PbCrO4 

0  010773 

8  03234 

Zn                        

0  .  003269 

7.51441 

BIBLIOGRAPHY 


The  following  is  a  list  of  those  books  which  we  have  found  to  be 
of  great  value  in  Analytical  Work.  It  does  not  claim  to  be  a 
complete  list,  but  a  representative  selection  of  books  which  will 
answer  the  questions  that  arise  in  the  course  of  routine  or  special 
analytical  work.  Prices  are  not  given,  because  they  are  changing 
from  time  to  time  and  it  will  doubtless  be  some  time  before  they 
reach  a  stable  condition. 

Handbooks 

HODGMAN,  C.  D. — Handbook  of  Chemistry  and  Physics.  7th  ed.  1918. 
Chemical  Rubber  Co.,  Cleveland,  Ohio. 

LINDELL,  D.  M. — Metallurgists'  and  Chemists'  Handbook.  2d  ed.  McGraw- 
Hill  Book  Co.,  Inc. 

MEADE,  R.  K  —  Chemists'  Pocket  Manual.  3d  ed.  1918.  Chemical  Pub- 
lishing Co.,  Easton,  Pa. 

OLSEN,  J.  C. — Van  Nostrand's  Chemical  Annual.  1918  ed.  D.  Van  Nos- 
trand  Co. 

SEIDELL,  A. — Solubilities  of  Inorganic  and  Organic  Substances.  2d  ed. 
1919.  D.  Van  Nostrand  Co. 

Qualitative  Analysis 
BASKERVILLE,  C.,  and  CURTMAN,  L.  J. — Course  in  Qualitative  Analysis.    2d 

ed.     1916.     The  Macmillan  Co.  . 

COHN,  A.  I. — Indicators  and  Test  Papers.     2d  ed.     Wiley  &  Sons. 
COHN,  A.  I. — Tests  and  Reagents.     1903.     Wiley  &  Sons. 
MERCK,  VON  E. — Chemical  Reagents,  their  Purity  and  Tests.     Translated 

by  Henry  Schenck.     2d  ed.     1914.     D.  Van  Nostrand  Co. 
MULLIKEN,  S.  P. — Methods  for  the  Identification  of  Pure  Organic  Compounds 
by  a  Systematic  Analytical  Procedure  Based  on  Physical  Properties 
and  Chemical  Reactions.     1904-1916.     Wiley  &  Sons. 
Volume      I.  Compounds  of  Carbon  with  Hydrogen  and  Oxygen. 
II.  Nitrogenous  Compounds. 
III.  Commercial  Dyestuffs. 
MURRAY,  B.  L.— Standards  and  Tests  for  Reagent  Chemicals.    1920.    D.  Van 

Nostrand  Co. 

NOTES,  A.  A. — Qualitative  Analysis  of  Inorganic  Substances.  6th  ed.  1915. 
The  Macmillan  Co. 

627 


628  BIBLIOGRAPHY 

PRESCOTT,  A.  B.,  and  JOHNSON,  O.  C. — Qualitative  Chemical  Analysis.  7th 
ed.,  revised  by  John  C.  Olsen.  1916.  D.  Van  Nostrand  Co. 

STEIGLITZ,  J.  O. — Elements  of  Qualitative  Analysis.  2  vols.  1911.  The 
Century  Co. 

TREADWELL,  F.  P. — Analytical  Chemistry.  I.  Qualitative  Analysis.  4th 
English  ed.  Translated  by  W.  T.  Hall.  1915.  Wiley  &  Sons. 

Quantitative  Analysis 

CLASSEN,  A. — Ausgewahlte  Methoden  der  analytischen  Chemie.  1901.  Fried- 
rich  Vieweg  und  Sohn,  Braunschweig,  Germany. 

MAHIN,  E.  G. — Quantitative  Analysis.  2d  ed.  1919.  McGraw-Hill  Book 
Co.,  Inc. 

OLSEN,  JOHN  C. — Textbook  of  Quantitative  Analysis.  5th  ed.  1916.  D.  Van 
Nostrand  Co. 

SUTTON,  F.— Volumetric  Analysis.     10th  ed.     1911.     Blakiston's  Son  &  Co. 

TREADWELL,  J.  C. — Analytical  Chemistry.  II.  Quantitative  Analysis.  4th 
English  ed.  Translated  by  W.  T.  Hall.  1916.  Wiley  &  Sons. 

Technical  Analysis — Inorganic 
AMERICAN  SOCIETY  FOR  TESTING  MATERIALS. — Triennial  Standards.     1918. 

See  also  supplementary  volume  for  1919. 
LUNGE,   GEORGE. — Technical   Methods  of  Chemical  Analysis.     Translated 

by  C.  A.  Keane.     3  vols.     1908-1914.      D.  Van  Nostrand  Co. 
SCOTT,  W.  W.— Standard   Methods   of   Chemical   Analysis.     2d   ed.     1917. 

D.  Van  Nostrand  Co. 
VILLAVECCHIA,  V. — Treatise  on  Applied  Analytical  Chemistry.     Translated 

by  T.  H.  Pope.     2  vols.     1918.     Blakiston's  Son  &  Co. 

Technical  Analysis — Organic 

ALLEN,  ALFRED  H. — rCommercial  Organic  Analysis.  9  vols.  1909-1917. 
A  Treatise  on  the  Properties,  Proximate  Analysis,  Analytical  Examina- 
tion, etc.  Blakiston's  Son  Co. 

GATTERMANN,  LUDWIG. — Practical  Methods  of  Organic  Chemistry.  Latest 
ed.  The  Macmillan  Co. 

MULLIKEN. — See  under  Qualitative  Analysis. 

SHERMAN,  H.  C. — Methods  of  Organic  Analysis.  3d  ed.  1912.  The  Mac- 
millan Co. 

SPECIAL  SUBJECTS 

Agriculture 
ASSOCIATION  OF  OFFICIAL  AGRICULTURAL  CHEMISTS. — Official  and  Tentative 

Methods  of  Analysis.     1920.     This  covers  also  such  subjects  as:   Foods 

and  Feeding  Stuffs,   Soils,   Fertilizers,   Insecticides,   Fruits,   Beverages, 

Meals,  Dairy  Products,  Food  Preservatives,  etc. 
WILEY,  HARVEY  W. — Principles  and  Practice  of  Agricultural  Analysis.     III. 

Agricultural  Products.     2d  ed.     1914.     Chemical  Publishing  Co.,  Easton, 

Pa. 


BIBLIOGRAPHY  629 

Alloys 

BLOUGH,  E. — Analysis  of  Aluminium  and  Its  Commercial  Alloys.  1910. 
Aluminum  Co.  of  America,  Pittsburgh,  Pa. 

JOHNSON,  C.  M. — Rapid  Methods  for  the  Chemical  Analysis  of  Special 
Steels,  Steel  Making  Alloys  and  Graphite.  3d  ed.  1920.  Wiley 
&  Sons. 

LORD,  N.  W.,  and  DEMOREST,  D.  J. — Metallurgical  Analysis.  4th  ed.  1916. 
McGraw-Hill  Book  Co.,  Inc. 

PRICE,  W.  B.,  and  MEADE,  R.  K. — Technical  Analysis  of  Brass  and  the  Non- 
ferrous  Alloys.  2d  ed.  1911.  Wiley  &  Sons. 

Asphalt 
ABRAHAM,  H. — Asphalt  and  Allied  Substances.    1918.    D.  Van  Nostrand  Co. 

Dyes 

GREEN,  A.  G. — Analysis  of  Dyestuffs  and  their  Identification  in  Dyed  and 
Colored  Materials,  etc.  1915.  Lippincott  Co. 

MULLIKEN. — See  Qualitative  Analysis. 

SCHULTZ,  G.,  and  JULIUS,  P. — Systematic  Survey  of  the  Organic  Coloring 
Matters.  5th  ed.  1914.  42d  Street  Commercial  Studio,  New  York 
City. 

WEISS,  J.  M.— Methods  of  Analysis  of  the  Coal-tar  Industry.  1918.  The 
Barrett  Co. 

Cement 

MEADE,  RICHARD  K.— Portland  Cement.  2d  ed.  1911.  Chemical  Pub- 
lishing Co.,  Easton,  Pa. 

Drugs  and  Chemicals 

PHARMACOPOEIA  OF  THE  UNITED  STATES. — IX  Decennial  revision.  1916. 
Blakiston's  Son  &  Co. 

Foods 

ALLEN. — See  Technical  Analysis — Organic. 

ASSOCIATION  OF  OFFICIAL  AGRICULTURAL  CHEMISTS. — See  Agriculture. 
LEACH,  A.  C.,  and  WINTON,  A.  L. — Food  Inspection  and  Analysis.     4th  ed. 

1920.     Wiley  &  Sons. 
WINTON,   A.   L. — Microscopy  of  Vegetable  Foods.     2d  ed.     1916.     Wiley 

&  Sons. 
WOODMAN,  A.  G.— Food  Analysis.     1915.     McGraw-Hill  Book  Co.,  Inc. 

Fuels 
BACON,  R.  F.,  and  HAMOR,  W.  A. — American  Petroleum  Industry.    2  vols. 

1916.     McGraw  Hill  Book  Co.,  Inc. 
CROSS,    R. — Handbook   of   Petroleum,    Asphalt,   and   Natural   Gas.     1919. 

Kansas  City  Testing  Laboratory. 
GILL,  A.  H. — Gas  and  Fuel  Analysis  for  Engineers.     8th  ed.     1917.     Wiley 

&Sons. 


630  BIBLIOGRAPHY 

HOLDE,  D. — Examination  of  Hydrocarbon  Oils.  Translated  by  E.  Mueller. 
1915.  Wiley  &  Sons. 

Gas  Analysis 

GAS  CHEMISTS'  HANDBOOK. — 2d  ed.  1920.  American  Gas  Association, 
New  York  City. 

HEMPEL,  WALTHER. — Methods  of  Gas  Analysis.  Translated  from  3d  Ger- 
man ed.  1906.  The  Macmillan  Co. 

WHITE,  ALFRED  H. — Technical  Gas  and  Fuel  Analysis.  2d  ed.  1920. 
McGraw-Hill  Book  Co.,  Inc. 

Iron  and  Steel 

BLAIR,  A.  A. — The  Chemical  Analysis  of  Iron.  8th  ed.  1918.  Lippin- 
cott  Co.  See  also  under  Alloys. 

Leather 

PROCTOR,  H.  R. — Leather  Industries'  Laboratory  Book  of  Analytical  and 
Experimental  Methods.  2d  ed.  1908.  Spon  &  Chamberlain. 

Minerals  and  Ores 
Low,  A.  H.— Technical  Methods  of  Ore  Analysis.     8th  ed.     1919.     Wiley 

&  Sons. 

Oils,  Fats  and  Soaps 
FRYER,  F.  E.,  and  WESTON,  P.  J. — Technical  Handbook  of  Oils,  Fats  and 

Waxes.     2d  ed.     1918.     University  Press,  Cambridge,  Eng.     Putnam's 

Sons. 

GILL,  A.  H. — Short  Handbook  of  Oil  Analysis.     8th  ed,     1918.     Lippincott. 
LAMBORN,  LLOYD  L. — Modern  Soaps,  Candles  and  Glycerin.    1906.     D.  Van 

Nostrand  Co. 
LEWKOWITSCH,  J. — Chemical  Technology  and  Analysis  of  Oils,  Fats  and 

Waxes.     5th  ed.     3  vols.     1913-1915.     The  Macmillan  Co. 
PICKERING,  G.  F. — Aids  in  the  Chemical  Analysis  of  Oils,  Fats  and  Their 

Commercial  Products.     1917.     Lippincott  Co. 

Paints  and  Varnishes 

GARDNER,  H.  A.,  and  SCHAEFFER,  JOHN  A. — Analysis  of  Paints  and  Painting 
Materials.  1911.  McGraw-Hill  Book  Co.,  Inc. 

HOLLEY,  C.  D. — Analysis  of  Paint  Vehicles,  Japans  and  Varnishes.  1920. 
Wiley  &  Sons. 

HOLLEY,  C.  D.,  and  LADD,  E.  F. — Mixed  Paints,  Color  Pigments  and  Var- 
nishes. 1908.  Wiley  &  Sons. 

TOCH,  M—  Chemistry  and  Technology  of  Paints.  2d  ed.  1916.  D.  Van 
Nostrand  Co. 

Paper  and  Cellulose 

BROMLEY,  H.  A. — Outlines  of  Stationery  Testing.     1913.     Lippincott  Co. 
GRIFFIN,  R.  B.,  and  LITTLE,  A.  D. — Chemistry  of  Papermaking.     1894.     G.  E. 
Stechert,  New  York  City. 


BIBLIOGRAPHY  631 

HERZBERG,    W.— Papierpriifung.     4th    ed.     1915.     G.    E.    Stechert,    New 

York  City. 
SCHWALBE,   C.   G.,   and  SIBBER,   R. — Chemische   Betriebskontrolle   in   der 

Zellstoff-  und  Papierindustrie.     1919.     G.  E.  Stechert,  New  York  City. 
STEVENS,  H.  P.— Paper  Mill  Chemist.     2d  ed.    1919.     D.  Van  Nostrand  Co. 
WITHAM,     G.     S. — Modern     Pulp     and     Papermaking.     1920.     Chemical 

Catalog  Co. 
WORDEN,  E.  C.— Technology  of  Cellulose  Esters.    Vol.  VIII.    1916.    D.  Van 

Nostrand  Co. 

Rubber 
HEIL,  A.,  and  ESCH,  W. — Manufacture  of  Rubber  Goods.      2d  ed.      1919. 

Griffin,  London. 
WEBER,  C.  O. — Chemistry  of  India  Rubber.     1903.     Lippincott  Co. 

Sugar 

BROWN,  C.  A. — Handbook  of  Sugar  Analysis.     1912.     Wiley  &  Sons. 
PRINSEN  GEERLIGS,  H.  C. — Chemical  Control  in  Cane  Sugar  Factories.     2d 
ed.     1917.     N.  Rodger,  London. 

Textiles 
BARKER,  A.  F.,  and  MIDGELY,  E. — Analysis  of  Woven  Fabrics.    1914.    D.  Van 

Nostrand  Co. 
KNECHT,  E.,  LOWENTHAL,  R.,  and  RAWSON,  C. — Manual  of  Dyeing.     3d  ed. 

2  vols.     1916.     Lippincott  Co. 

MATTHEWS,  J.  M.— The  Textile  Fibers.     3d  ed.     1913.     Wiley  &  Sons. 
MITCHELL,  C.  A.,  and  PRIDEAUX,  R.  M.— Fibers  Used  in  Textile  and  Allied 

Industries.     1910.     Scott,  Greenwood  &  Son,  London. 

Water 
AMERICAN   PUBLIC    HEALTH   ASSOCIATION. — Standard    Methods   of   Water 

Analysis.     3d  ed.     1917.     American  Public  Health  Association,  Boston. 
MASON,  W.  P.— Examination  of  Water.     5th  ed.     1917.     Wiley  &  Sons. 
PRESCOTT,  S.  C.,  and  WINSLOW,  C.-E.  A. — Elements  of  Water  Bacteriology, 

with   Special   Reference   to   Sanitary   Water  Analysis.     3d   ed.     1913. 

Wiley  &  Sons. 
RICHARDS,  ELLEN, — Conservation  by  Sanitation.     1911.     Wiley  &  Sons. 

GOVERNMENT  PUBLICATIONS 

The  following  bulletins  from  the  various  Government  Bureaus 
mentioned  below  deal  in  whole  or  in  part  with  analytical  methods 
which,  as  mentioned  in  the  preface,  have  been  freely  used  in  the 
preparation  of  the  methods  of  analysis  given  in  this  book. 

Bureau  of  Chemistry 

BULLETIN   66.— Fruits   and   Fruit   Products:    Chemical   and   Microscopical 
.Examination.     1902. 


632  BIBLIOGRAPHY 

BULLETIN  79. — Testing  of  Road  Materials,  Including  Methods  Used  and 

Results  Obtained  in  Road  Material  Laboratory  in  Collaboration  with 

Office  of  Public-road  Inquiries.     1903. 
BULLETIN  91. — Mineral  Waters  of  United  States.     1905. 
BULLETIN  108. — Commercial  Feeding  Stuffs  of  United  States,  their  Chemical 

and  Microscopical  Examination.     1908. 
BULLETIN  109. — Some  Technical  Methods  of  Testing  Miscellaneous  Supplies, 

Including  Paints  and  Paint  Materials,  Inks,  Lubricating  Oils,   Soaps, 

etc.     1908. 
BULLETIN  114. — Meat  Extracts  and  Similar  Preparations,  Including  Studies 

of  Methods  of  Analysis  Employed.     1908. 
BULLETIN  135. — Commercial  Turpentines,  their  Quality  and  Methods  for 

their  Examination.     1911. 

BULLETIN  147.— Coal-Tar  Colors  Used  in  Food  Products.     1912. 
CIRCULAR  25. — Coloring    Matters   for  Foodstuffs  and    Methods   for   their 

Detection.     1905. 
CIRCULAR  63. — Identification  of  Food  Colors,  Tentative  Report  on  Solubility 

and  Extraction  of  Certain  Colors  and  Color  Reactions  of  Dyed  Fiber  and 

of  Aqueous  and  Sulfuric  Acid  Solutions.     1911. 
CIRCULAR  89. — Quantitative  Separation  of  Mixtures  of  Certain  Acid  Coal-Tar 

Dyes.     1912. 

CIRCULAR  107. — Detection  of  Faulty  Sizing  in  High-grade  Papers.     1913. 
CIRCULAR  113. — Quantitative  Separation  and  Determination  of  Subsidiary 

Dyes  in  Permitted  Food  Colors.     1913. 

Bureau  of  Mines 
BULLETIN  12. — Apparatus  and  Methods  for  the. Samplings  and  Analysis  of 

Furnace  Gases.     1911. 
BULLETIN  42. — The  Sampling  and  Examination  of  Mine  Gases  and  Natural 

Gas.     1913. 

BULLETIN  97. — Sampling  and  Analysis  of  Flue  Gases.     1915. 
BULLETIN  116. — Methods  of  Sampling  Delivered  Coal,  and  Specifications  for 

the  Purchase  of  Coal  for  the  Government.     1916. 
BULLETIN  125. — The  Analytical  Distillation  of  Petroleum.     1916. 
TECHNICAL  PAPER  8. — Methods  of  Analyzing  Coal  and  Coke.     1913. 
TECHNICAL  PAPER  25. — Methods  for  the  Determination  of  Water  in  Petro- 
leum and  its  Products.     1912. 
TECHNICAL  PAPER  26. — Methods  for  the  Determination  of  the  Sulfur  Content 

of  Fuels,  Especially  Petroleum  Products.     1912. 

TECHNICAL  PAPER  31. — Apparatus  for  the  Exact  Analysis  of  Flue  Gas.     1913. 
TECHNICAL  PAPER  49. — The  Flash  Point  of  Oils;  Methods  and  Apparatus  for 

its  Determination.     1913. 

TECHNICAL  PAPER  148. — The  Determination  of  Moisture  in  Coke.     1917. 
TECHNICAL  PAPER  166. — Motor  Gasoline;  Properties,  Laboratory  Methods  of 

Testing,  and  Practical  Specifications.     1917. 
TECHNICAL  PAPER  186. — Methods  for  Routine  Work  in  the  Explosive  and 

Physical  Laboratory  of  the  Bureau  of  Mines.     1918. 


BIBLIOGRAPHY  633 

TECHNICAL  PAPER  212. — The  Determination  of  Combustible  Matter  in  Sil- 
icate and  Carbonate  Rocks.  1919. 

TECHNICAL  PAPER  214. — Motor  Gasoline;  Properties,  Laboratory  Methods 
of  Testing,  and  Practical  Specifications.  1919. 

Bureau  of  Standards 

CIRCULAR  19. — Standard  Density  and  Volumetric  Tables.  1916. 
CIRCULAR  25. — Standard  Samples — General  Information.  1917. 
CIRCULAR  33. — United  States  Government  Specification  for  Portland  Cement. 

1917. 

CIRCULAR  38. — The  Testing  of  Rubber  Goods.     1915. 
CIRCULAR  41. — Testing  and  Properties  of  Textile  Mater  als.     1918. 
CIRCULAR  45. — The  Testing  of  Materials. 
CIRCULAR  48. — Standard  Methods  of  Gas  Testing.     1916. 
CIRCULAR  62. — Specifications  for  and  Methods  of  Testing  Soaps.     1919. 
CIRCULAR  95. — Inks — Their  Composition,    Manufacture,   and   Methods   of 

Testing.     1920. 

Geological  Survey 
BULLETIN  700.— Analysis  of  silicate  and  carbonate  rocks.     1919. 


INDEX 


Abb£  refractometer,  use  of 

Abietic  acid  in  rosin 

Abrams  and  Harder  color  test  for  sand. . 

Abrasive  in  metal  polish 

Absorption  test  of  blotting  paper 

Acetaldehyde,  standard  solution  of .... 
Acetate  of  lime  (See  Calcium  acetate) . 

Acetate  silk 

Acetates  in  carbolineum 

— ,  qualitative  test  for 

Acetic  acid  in  acetate  of  lime 

carbolineum 

— ethyl  alcohol 

lead  arsenate 

"light  vinegar" 

pyroligneous  acid. .  , 

vinegar 

wood  acid 

wood  distillate 

wood  preserving  oils 

— ,  crude,  analysis  of 

,  qualitative  test  for 

,  reagent 

,  anhydride,  analysis  of 

,  aniline  method  for 

,  boiling  point  of 

,  direct  titration  of 

Acetin  method  for  glycerol.  . 

Acetone  in  wood  alcohol 72, 

— ,  Messinger  method  for 

—  extract  of  rubber 

Acetyl  number    (See  Acetyl  value). 

—  value  of  oils 

Acetylene  equivalent  of  calcium  carbide 

Acetylization  of  glycerol 

oils 

Acid    (See  also  Acidity). 

—  in  leather 

lubricating  oils 

vinegar 

— ,  abietic,  in  rosin 

— ,  acetic    (See  Acetic  acid). 

— ,  arachidic,  melting  point  of 

— ,  arsenious,  0.1    N  solution  of 

— ,  benzoic,'  heating  value  of 

— ,  butyric,  in  oils 

— ,  carbolic,  in  soap  (reference) 


231 
328 
580 
490 
354 
76 

380 

535 

535 

32 

535 

74 

49 

370 

369 

457 

370 

369 

535 

370 

535 

1 

82 

83 

84 

82 

85 

371 

72 

480 

244 

486 

85 

244 

475 
260 
456 
328 

251 
11 

178 
243 

288 


Acid,  carbonic    (See  Carbon  dioxide). 

— ,  chlorplatinic,  preparation  of 16 

— ,  formic,  analysis  of 81 

— ,  — ,  in  vinegar 457 

— ,  hydrochloric,  in  formic  acid 81 

— ,  — ,  reagent 8 

— ,  — ,  volumetric  solutions  of 7,  8 

— ,  lactic,  in  cheese 452 

— ,  lead,  preparation  of 138 

— ,  malic,  in  vinegar 456 

— ,  mineral,  in  leather 475 

— ,  — ,  —  lubricating  oils 260 

— ,  nitric,  reagent 4 

— ,  — ,  red  fuming,  reagent 4 

— ,  — ,  test  for  groundwood 339 

—  number  of  beeswax 276 

fats  and  oils 242 

rosin 328 

— ,  oxalic,  0.  IN  solution  of 8 

— ,  picric,  test  for  gelatin 448 

— ,  phosphoric     (See    Phosphoric   acid 

and  Phosphoric  anhydride). 
— ,  prussic    (See  Hydrocyanic  acid). 

— ,  stearic,  in  beeswax 278 

— ,  sulfite,  analysis  of 301 

— ,  — ,  composition  of 301,  302 

— ,  sulf uric    (See  also  Sulfur  trioxide) . 

— ,  — ,  in  aluminum  sulfate 304 

— ,  — ,  —  fdrmic  acid 81 

— ,  — ,  —  leather 475 

— ,  — ,  —  sulfite  acid 301 

— ,  — ,  free,  in  aluminum  sulfate 305 

— , — .fuming    (See  Oleum). 

— ,  — ,  reagent 5 

— ,  — ,  38  Normal 197 

— ,  sulfurous    (See  also  Sulfur  dioxide). 

— ,  — ,  in  paper 342 

— ,  — ,  —  sulfite  acid 301 

— ,  tannio,  analysis  of 95 

— ,  value    (See  Acid  number). 

— ,  — ,  malic,  of  maple  products 427 

— ,  wood,  analysis  of 370 

Acidity  of  aluminum  sulfate 305 

casein 317 

cheese 452 

ethyl  alcohol 74 

f eedstuffs  and  grains 442 


635 


636 


INDEX 


Acidity  of  gasoline 187 

• glue.  . 320 

leather 475 

paper 342 

Acids,  fatty    (See  Fatty  acids). 
— ,  tar    (See  Tar  acids). 

Acorn  oil,  constants  of 232 

Adams   method   for  fat  in   condensed 

milk 450 

Agalite  in  paper 341 

Aggregate  for  concrete 576 

Air-compressor  oil,  testing  of 254 

Alba  whiting,  composition  of 201 

Albrech  test  for  lemon  peel  color 463 

orange  peel  color 463 

Albumin,  analysis  of 93 

— ,  blood-serum 93 

— ,  egg 93 

— ,  soluble    coagulable,    determination 

of 94 

Albuminoid  nitrogen  in  feedstuff s 439 

— water 502 

Alcohol,      aldehyde-free,      preparation 

of 75,  460 

— ,  amyl    (See  Fusel  oil) 

— ,  ethyl,  in  brandy  drops 419 

— ,  — ,  —  confectionery  syrups 419 

— ,  — ,  —  lemon  extract 458 

— ,  — ,  —  orange  extract 458 

— ,  — ,  —  peppermint  extract 467 

— ,  — ,  —  spearmint  extract 467 

— ,  — ,  —  syrups 419 

— ,  — ,  —  vanilla  extract 468 

— ,  — ,  —  vinegar 454 

— ,  — ,  —  wintergreen  extract 467 

— ,  — ,  analysis  of 74 

— ,  by  volume 459 

— ,  —  weight 458 

—  tables  (reference) 74,  419,  454 

— ,  grain    (See  Alcohol,  ethyl).  . 

— ,  methyl    (See  Methyl  alcohol). 

— ,  wood,  crude,  in  wood  distillate.  .  .  .  369 

Alcoholic  potash  extract  of  rubber ....  482 

Alcoholic  potash,  0. 5  N  solution  of . .  .  1,  29 

Aldehyde  in  alcohol,  silver  nitrate  test 

for 75 

ethyl  alcohol 75 

lemon  extract 460 

orange  extract 460 

— ,  Chace  method  for 460 

free  alcohol,  preparation  of 75,  460 

— ,  sulfite  f uchsin  method  for 75 

Alizarin  lakes,  composition  of 202 

Alkali  in  casein 315 

rosin  size 330 

rosin  size  milk 332 

soap 280,  282,  283 

Alkalies,  analysis  of 19 


Alkalies,  in  water 518 

— ,  qualitative  tests  for 20 

Alkalimeter,  Mohr,  for  COz  determina- 
tion (Fig.  13) 212 

Alkalinity  of  black  sulf  ate  liquor .  .  296,  297 
cocoa 431 

—  —  glue 320 

white  sulf  ate  liquor 299 

Allihn  method  for  dextrose 407 

Fehling's  solutions 3,  407 

Alloy  steel,  analysis  of 116 

Alloys,  aluminum,  analysis  of 160 

— ,  Babbitt,  analysis  of 157 

— ,  brass  and  bronze,  analysis  of 142 

— ,  German  silver,  analysis  of 152 

— ,  nickel  silver,  analysis  of 1 52 

— ,  solder,  analysis  of 154 

— ,  type  metal,  analysis  of 158 

— ,  white,  analysis  of 154,   160 

— ,  zinc  amalgam,  analysis  of 163 

Almond  oil,  constants  of 232 

Alternate  shovel  method     of     reducing 

samples 170 

Alum,  paper  makers',  analysis  of 303 

— ,  resistance  of  ultramarine  to 336 

Alumina  in  aluminum  sulf  ate 303 

blanc  fixe 310 

boiler  scale 523 

chrome  yellow 216 

Portland  cement 574 

salt 25 

water 518 

— ,  basic,  in  aluminum  sulfate 305 

—  cream,  preparation  of 2,  399 

Aluminum  in  aluminum  alloys 160 

brass  and  bronze 151 

—  alloys,  analysis  of . . . : 160 

—  foil  method  for  nitrates 507 

—  hydroxide  for  clarifying  water 510 

in  satin  white .  .• 332 

—  oxide    (See  Alumina) 

—  sulfate,  analysis  of 303 

Amalgam,  zinc,  analysis  of 163 

Amalgamated  zinc,  preparation  of.  ...    149 

Amalgamation  of  brass 542 

American  Elect.  Ry.  Eng.  Assoc.    tin- 
ning test 166 

—  Pulp  and  Paper  Assoc.  method  for 

wood  pulp  testing 293 

—  Tel.  and  Tel.  Co.  tinning  test 166 

—  test  on  paraffin  wax 279 

—  vermilion,  composition  of 202 

Amido  nitrogen  in  feedstuffs  and  grains.  440 
Amidonaphthalene  acetate  reagent  for 

nitrites 504 

Aminoazotoluene,  separation  of. 392 

Ammonia      (See  a.lso  Ammonium  hy- 
droxide), 


INDEX 


637 


Ammonia,  analysis  of 23 

— ,  aqua,  U.  S.  P 23 

—  in  ammonia  liquors 23 

ammonium  hydroxide 23 

case-hardening  compounds 485 

eggs 387 

fertilizers 525 

lead  arsenate 49 

metal  polishes 490 

organic  materials 68 

soldering  paste 491 

— ,  nesslerization  method  for 501 

— ,  titration  with  methyl  orange 66 

—  liquor,  analysis  of 23 

—  nitrogen  in  sewage 501 

— ,  — ,  albuminoid,  in  water 502 

— ,  — ,  free,  in  water 498 

— ,  — ,  magnesia  method  for 68 

—  water,  analysis  of 23 

—  and  nitric  nitrogen 68 

Ammoniacal  silver  nitrate  solution.  . . .    299 
Ammonium  acetate  reagent 2 

—  carbonate  reagent 2 

—  chloride  reagent 2 

in  soldering  paste 491 

—  citrate  solution,  preparation  of 525 

—  hydroxide,  analysis  of 23 

reagent 2 

—  molybdate  solution  for  phosphorus 

in  steel 113 

P2O5  in  fertilizers 525,  528 

reagent 2 

—  nitrate  reagent 2 

—  oxalate  reagent 2 

—  phosphate  reagent 3 

—  phosphomolybdate,  preparation  of .  .    113 

—  polysulfide  reagent 3 

—  sulf ate  reagent 3 

,  moisture  in 525 

—  sulfide  reagent 3 

—  sulfocyanate,  0. 1  N  solution 11 

Amyl  alcohol    (See  Fuseloil). 

Analytical  factors,  tables  of 608,  615 

Anchovy  oil,  constants  of 232 

Anhydrides,  analysis  of 82 

Aniline  chloride  test  for  invert  sugar.. .   424 

—  dyes,  testing  of 307 

—  method  for  acetic  anhydride 83 

—  sulf  ate  test  for  ground  wood 338 

—  yellow,  separation  of 392 

Animal    and    vegetable    oils    and    fats, 

analysis  of 230 

—  size    (See  Glue). 

Annatto,  separation  of 392 

Antimonious  acid  (See  Antimony  oxide). 
Antimony,  golden  sulfide  of 34 

—  in  Babbitt  metals 157 

brass  and  bronze.  .  .  .    150 


Antimony  in  solder 155 

type  metals 159 

white  metals 155 

— ,  permanganate  method  for 150,  155 

—  oxide  in  antimony  sulfide 35 

—  sulfide,  analysis  of 34 

Anti-tarnish  paper,  testing  of 362 

Apricot  kernel  oil,  constants  of 232 

Aqua  ammonia,  U.  S.  P 23 

—  regia 157 

Arabinose,  Allihn  method  for 408 

Arachidic  acid,  melting  point  of 251 

method  for  peanut  oil 250 

Arachis  oil    (See  Peanut  oil). 

Archil,  dyeing  test  for 390 

Armature  insulating  varnish,  specifica- 
tions for 227 

,  testing  of 227 

Arnold-Kjeldahl-Gunning    method    for 

nitrogen 66 

Arsenate  of  lead   (See  Lead  arsenate) . 
Arsenic,  determination  of  small  amounts 

of 35 

— ,  distillation  method  for     55,  149 

— ,  Gutzeit  (modified)  method  for 37 

—  in  alloys 149 

beer 35,  39 

Bordeaux     mixture     with     lead 

arsenate .  54 

with  Paris  green 53 

brass  and  bronze 149 

chemicals 35,  39 

drugs 35,  39 

foods 35,  40 

lead  arsenate 47 

lead  arsenate  with  Bordeaux  mix- 
ture    54 

paper 40 

Paris  green 55 

Paris  green  with  Bordeaux  mix- 
ture    53 

textiles 40 

wall  papers 40 

— ,  Marsh  test  for 36 

— ,  Sanger-Black-Gutzeit  method  for.  .  37 

— ,  titration  with  iodine 47 

— ,  water-soluble,  in  lead  arsenate 49 

—  bronze,  analysis  of 149 

—  mirrors,  preparation  of  standard ....  37 

—  oxide    (See  also  Arsenic). 

in  lead  arsenate 47 

Arsenious  acid,  0. 1  N  solution  of 11 

—  oxide  in  Paris  green 56 

,  C.  C.  Hedges  method  for 56 

,  C.  M.  Smith  method  for 57 

,  sodium  acetate-soluble,  in  Paris 

green 57 

,  water-soluble,  in  Paris  green... .  57 


638 


INDEX 


Asbestine,  composition  of 201 

—  in  paper. 341 

Asbestos    in     asbestos-magnesia     pipe 

covering 63 

— ,  purification  of. 403,  405 

—  cotton  twine,  analysis  of . . 385 

magnesia    pipe    covering,    analysis 

of 62 

,  composition  of 62 

Ash  of  albumin 94 

asphalt 546 

bituminous  materials 546 

black  sulfate  liquor 295 

butter 428 

carbolineum 535 

casein 315 

cheese 452 

chocolate  and  cocoa 431 

coal 174 

cotton  linters 364 

• glue 320 

• grease 272 

honey 420 

indigo 99 

leather 474 

milk 444 

paper 340 

rope  and  twine 383 

rubber  compounds. " 483 

saccharine  products 413 

,  electrolytic  method  for...  .    414 

sulfonated  oil 264 

sulfur 17 

tallow 270 

textile  fabrics 372 

tobacco 102 

varnish 220 

vinegar 456 

wood-preserving  oils.1 535 

— ,  sulfate  method  for 94,  414 

— ,  sulfated,  of  albumin 94 

Ashes,  coal,  analysis  of 185 

Asphalt  products  in  tar,  test  for 547 

Asphaltic  road  binders,  analysis  of ....    537 

Assaying  of  tin  ores 136 

Association  of  American   Wood    Pulp 
Importers'  method  for  wood  pulp 

testing 293 

Astringency  of  sumac  extract 479 

Atomic  weights,  table  of 584 

—  group  weights,  table  of 586 

Auramine,  separation  of 392 

Auramine  O,  behavior  on  dyeing 390 

Automobile  oil,  testing  of 254 

Available  chlorine  in  bleach 312 

—  organic  nitrogen 69 

Azotometer  method  for  nitrogen  (refer- 
ence)        67 


B.t.u.     (See    British   thermal   units). 

Babbitt  metals,  analysis  of 157,  158 

Babcock  method  for  fat  in   milk   and 

cream 446 

—  test  bottles 446 

Ball  and  ring     method     for     softening 

point 543 

Bardy  and  Riche  test  for  methyl  alcohol  462 

Barium  carbonate  in  blanc  fixe 310 

paper 341 

—  chloride  in  salt 26 

reagent 3 

—  hydroxide  reagent 8 

—  phosphate  in  blanc  fixe 310,  311 

—  sulfate  in  blanc  fixe 311 

—  sulfate  in  paint  pigments 207 

paper 341 

paper  coating 344 

Barytes    (See  also  Barium  sulfate). 

— ,  composition  of 201 

Basicity  of  aluminum  sulfate 305 

Battery  zinc  amalgams,  analysis  of .  .  .  .    163 

Baudouin  test  for  sesame  oil 252 

Baume  and  Brix  comparison  table 411 

—  gravity,     temperature     corrections 

(reference) 255 

and  specific  gravity,  comparison 

table 411 

of  oils,  relation  of 255 

Bear  oil,  constants  of 232 

Beechnut  oil,  constants  of 232 

Beef  fat  in  lard,  Emery  test  for 253 

—  marrow,  constants  of 232 

—  tallow,  analysis  of 268 

,  constants  of 232,  269 

Beer,  arsenic  in 39 

— ,  coal-tar  dyes  in 389 

— ,  sulfur  dioxide  in 396 

Beeswax,  adulterants  of 275,  277 

— ,  analysis  of 275 

— ,  constants  of 232,  277 

—.bleached 275 

— ,  Indian 277 

Beet  products,  sugar  in 401 

Bellier  test  for  peanut  oil. 252 

— . sesame  oil 253 

Ben  oil,  constants  of 232 

Benzene-insoluble   matter  in   carbolin- 
eum     535 

coal-tar  roofing  pitch 536 

wood-preserving  oils 535 

Benzeneazobetanaphthylamine,    separ- 
ation of 392 

Benzine 186 

Benzoic  Acid,  heating  value  of 178 

Benzol    (See  Benzene). 
Bertrand  and  Javillier  method  for  nico- 
tine. ..  .    101 


INDEX 


639 


Beverages,  coal-tar  dyes  in 389 

Bibliography  of  reference  books 627 

Bicarbonate  in  alkalies 20 

Bichloride  of  mercury     (See    Mercuric 
chloride) . 

Bichromate  method  for-  glycerol 89 

metallic  zinc 141 

—  of    potash    (See   Potassium   bichro- 

mate) . 

soda    (See  Sodium  bichromate). 

Bichromates,  volumetric  method  for. .  .  30 

Binder,  asphalt  road,  analysis  of 537 

Birotation  of  honey 421 

— ,  overcoming  of 415 

Bismuthate  method  for  manganese .  1 10,  147 

Bisulfite  liquor,  analysis  of 301 

,  composition  of 301,  302 

Bitumen  in  bituminous  materials 544 

—  insoluble  in  86°  naphtha 546 

—  soluble  in  carbon  bisulfide 544 

Bituminous  road  binders,  analysis  of .  .  537 
Black-Gutzeit-Sanger    method    for    ar- 
senic    37 

Black  insulating  varnish,  analysis  of. . .  .  227 

—  liquor  (sulfate),  analysis  of 295 

—  oil,  testing  of 254 

—  pigments,  classification  of 201 

Blanc  fixe,  analysis  of 308 

,  composition  of 201,  308 

for  photographic  purposes 309 

in  paper 34 1 

paper  coating 344 

.  silver  nitrate  test  of 309 

Bleach,  analysis  of 312 

— ,  Bunsen's  method  for 313 

—  consumption  of  pulp 313 

—  liquor,  analysis  of 314 

Bleaching,  determination  of  excessive. .  368 

—  powder,  analysis  of 312 

Blood  serum  albumin,  analysis  of 93 

Blotting  paper,  absorption  test  of 354 

Blue  pigments,  classification  of 203 

Bluing  in  clay 319 

— ,  turpentine  test  for 319 

Boemer  method  for  unsaponifiable  mat- 
ter in  oils 262 

Boiler  scale,  analysis  of 522 

—  water,  analysis  of 514 

,  grading  of 521 

Boiling  point  of  turpentine 194 

Bomb  calorimeter    (See  Calorimeter). 

Bone  black,  composition  of 201 

—  fat,  constants  of .  .  .  .  : 232 

—  fertilizers,  analysis  of . 524 

—  oil,  constants  of 232 

Books,  reference 627 

Borates,  qualitative  test  for 284 

Borax  in  soap 283 


Bordeaux  mixture,  analysis  of 50 

,  standard 50 

with  lead  arsenate,  analysis  of ...      54 

Paris  green,  analysis  of 52 

Borneo  tallow,  constants  of 132 

Boron    (see  also  Boric  acid  and  Borates). 

Bottlenose  oil,  constants  of 232 

Boughton  method  for  gums  in   varnish 

(reference) 217 

Brandy  drops,  alcohol  in 419 

Brass,  amalgamation  of 542 

— y,  analysis  of 142 

Brazilnut  oil,  constants  of 232 

Breaking  factor  of  paper 347 

—  length  of  paper 346 

Brimstone    (See  Sulfur). 

Briquettes,  cement,  preparation  of ....    569 

— ,  — ,  storage  of 571 

British  gum    (See  Dextrin). 
British  thermal  units  and  calories,  rela- 
tion of 178 

in  coal 176 

coal  ash 185 

liquid  fuels 190 

per  gallon 191 

Brix  and  Baume  gravity  comparison 

table 411 

Brix  hydrometer 410 

,  temperature  corrections  for 413 

Bromine  absorption  of  wood  alcohol. . .    .73 

—  test  for  fish  oils 254 

Bronze,  analysis  of 142 

Brown  pigments,  classification  of.,.  ...    203 

Browne  heating  test  for  tung  oil 199 

Bryan-Fiehe  test  for  invert  sugar 423 

Bunsen's  method  for  chlorine  in  bleach.    313 
Burning  point    (See  Fire  point). 

—  test    (See  Fire  point) . 

Burnt  sienna    (See  Sienna,  burnt). 
Bursting  factor  of  paper .' 349 

—  ratio  of  paper 349 

—  strength  of  paper 349 

textile  fabrics 373 

Butter,  analysis  of 427 

— ,  composition  of 427 

— ,  standard 429 

—  fat,  constants  of 232 

in  butter  substitutes 428 

milk  .chocolate 437 

,  standard 429 

— ,  kokum,  constants  of 234 

— ,  nutmeg,  constants  of 236 

— ,  renovated,  test  for 429 

—  scotch,  fat  in 418 

— ,  shea,  constants  of 238 

—  substitutes,  analysis  of 427 

,  preparation  of 427 

—  yellow,  separation  of 392 


640 


INDEX 


Butterine,  analysis  of 427 

Butyric  acid  in  oils 243 

—  anhydride,  analysis  of 84 

Butyro-refractometer  degrees  to  refract- 
ive index,  conversion  of 240 

—  Zeiss,  use  of 240 

Cacao  butter    (See  Cocoa  butter) 

—  products,  analysis  of 430 

,  artificial  coloring  in 391 

Cadmium,  electrolytic  method  for 141 

—  in  zinc 140 

— ,  sulfate  method  for 140 

Caffein  in  cocoa  and  chocolate 435 

Calcium  acetate,  analysis  of 32 

—  carbide     in     case-hardening     com- 

pounds   486 

,  acetylene  equivalent  of 486 

—  carbonate  in  paper 341 

talc 334 

—  chloride  reagent 3 

—  hydroxide  reagent 3 

in  satin  white 333 

—  hypochlorite    (See  Bleach). 

—  oxide    (See  Lime). 

—  sulfate,  analysis  of 319 

in  antimony  sulfide 35 

talc 335 

,  separation  from  magnesium  sul- 
fate   301 

Calender  oil,  testing  of 254 

Calories  and  B.t.u.,  relation  of .  .  • 178 

Calorimeter,  standardization  of 178 

Calorimetric  analysis  of  coal 176 

liquids 190 

Calophony    (See  Rosin). 

Calophyllum  oil,  constants  of 232 

Cameline  oil,  constants  of 232 

Canari  oil,  constants  of . 232 

Canary  chrome  yellow,  composition  of.  202 

Candies,  analysis  of 409 

— ,  artificial  coloring  in 390 

Candlenut  oil,  constants  of . . , 232 

Canned  goods,  artificial  coloring  in. ...  391 

Capsules  for  calorimetric  work 191 

Carapa  fat,  constants  of 232 

Carbide,  calcium,  acetylene  equivalent 

of. 486 

Carbohydrates      in      feedstuffs       and 

grains 440 

Carbolic  acid  in  soap  (reference) 288 

Carbolincum,  analysis  of 530 

Carbon,  colorimetric  method  for 131 

— ,  combustion  method  for 108 

—  in  coal 182 

iron,  colorimetric  method  for. ...  131 

,   solution-combustion   method 

for...                            130 


Carbon  in  steel 108 

tar 551 

— ,  combined,  in  iron 131 

— ,  — ,  —  steel 110 

— ,  fixed,  in  bituminous  materials 546 

— ,  — ,  —  coal 174 

— ,  free,  in  tar 545,  551 

— ,  graphitic,  in  iron 131 

— ,  — ,  —  paint 207 

— ,  — ,  —  steel 110 

—  bisulfide  extract  of  bituminous  ma- 

terials   544 

spent  oxide 555 

test  of  sulfur 17 

—  black,  composition  of 201 

—  dioxide,  alkalimeter  method  for.  .  .  .  212 

in  alkalies 20,  22 

Bordeaux  mixture 51 

water 515 

white  lead 212 

,  solid,  preparation  of 257 

—  furnace  (Fig.  6) 108 

—  steel    (See  Steel). 

—  tetrachloride,  purification  of 77 

Carbonate  in  alkalies 20 

Carbonates,  titration  of,  with  methyl 

orange 7,  22 

Carbonic  acid    (See  Carbon  dioxide). 

Carnaiiba  wax,  constants  of 232 

Case-hardening    compounds,     analysis 

of 484 

Casein,  analysis  of 315 

— ,  clay-carrying  capacity  of 316 

— ,  "cutting  test"  of 316 

— ,  foreign  and  domestic 316 

— ,  formaldehyde  test  for 344 

—  in  albumin,  qualitative  test  for 94 

butter 428 

milk 444 

milk  chocolate 435 

paper  coating 344 

— ,  muriatic  flakeless 316 

— ,  solubility  of 316 

Cassell  earth    (See  Vandyke  brown) . 

Cassiterite 134 

Cast  iron,  analysis  of 129 

,  sampling  of 106,  129 

Castor  oil,  analysis  of 263 

,  constants  of 232,  363 

Cattle  foods,  analysis  of 438 

Caustic  alkali  in  soap 282 

,  test  for 20 

—  alkalies,  analysis  of 19 

—  potash    (See  Potassium  hydroxide) . 

—  soda    (See  Sodium  hydroxide) . 

—  solutions,  volumetric 8 

Cedar  nut  oil,  constants 232 

Celestron  silk .  380 


INDEX 


641 


Cellulose  for  nitration,  analysis  of 363 

—  in  cotton  linters 365 

wood 289 

— ,  caustic  method  for 365 

— ,  sulfuric  acid  method  for 365 

—  acetate  silk 380 

Cement,  Portland,  chemical  analysis  of .  572 

— ,  — ,  composition  of 572 

— ,  — ,  in  mortar  and  concrete 560 

• — ,  — ,  physical  testing  of 561 

— ,  — ,  sampling  of 563 

— .  — •  specifications  for 5C1,  572 

• —  briquettes,  preparation  of 569 

,  storage  of 571 

—  testing  machine  (Fig.  29) 570 

Cereal  products,  artificial  coloring  in.  .  391 

Ceresin,  constants  of 232 

Chace  method  for  aldehyde  in  extracts  460 

• citral 460 

Chalk,  composition  of 201 

—  in  paper 341 

paper  coating 344 

Charcoal  black,  composition  of 201 

—  iron,  analysis  of 129 

,  sampling  of 106,  129 

Chardonnet  silk 379 

Chaulmoogra  fat,  constants  of 232 

Cheese,  analysis  of 451 

— ,  standard  for 451 

Cherry  kernel  oil,  constants  of 232 

—  laurel  oil,  constants  of 232 

Chicken  fat,  constants  of 232 

China  clay    (See  Kaolin). 

—  wood  oil    (See  also  Tung  oil). 

Chinese  wax,  constant%of 232 

—  wood  oil    (See  also  Tung  oil). 

,  constants  of 198,  234 

Chlorate  in  bleach 312 

—  method  for  manganese 148 

Chlorides    (See  also  Chlorine) . 

—  in  cyanides 32 

paper 343 

soap 285 

sodium  silicate 30 

water  and  sewage 509 

— ,  gravimetric  method  for 27,  81 

— ,  volumetric  method  for 509 

Chlorination  method  for  cellulose 289 

Chlorine    (See  also  Chlorides). 

—  in  bleach 312 

—  - —  boiler  scale 524 

butter 428 

paper 343 

sewage 509 

soldering  paste 492 

water 509 

— ,  available,  in  bleach 312 

— ,  volumetric  method  for 509 


Chloroform  extract  of  rubber 482 

Chlorplatinic  acid,  preparation  of 16 

Chocolate,  analysis  of 430 

— ,  bitter,  standard 430 

— ,  coloring  matter  in 391 

— ,  milk,  standard 430 

— ,  plain,  standard 430 

— ,  sweetened,  standard 430 

—  liquor,  standard 430 

Cholesterol  in  fats -.  .  .    247 

Cholesteryl  acetate,  melting  point  of. . .   249 
Chromate  method  for  lead.  .  .  .47,  208,  212 
Chrome  green,  composition  of 203 

—  leather,  chromium  in 478 

—  liquid,  analysis  of 477 

—  orange,  composition  of 202 

—  oxide  green,  composition  of 203 

—  red,  composition  of 202 

—  salts,  chromium  in 477 

—  steel,  analysis  of 116 

—  tanning  liquors,  chromium  in 477 

vanadium  steel,  analysis  of 116 

• —  yellow,  analysis  of 213 

—  yellows,  composition  of 202 

Chromium  in  chrome  leather 478 

tanning  liquors 477 

yellow 215 

chromium  acetate 477 

salts 477 

steel 122,   125 

— ,  lead  chromate  method  for. . ., .  .  215,  478 

— ,  permanganate  method  for 122 

— ,  peroxide  method  for 208,  215,  477 

— ,  volumetric  method  for 216,  477 

—  ajid  vanadium,  double  titration  of. .    125 

—  steel,  analysis  of 116 

Chrysalis  oil,  constants  of 232 

• ,  Japanese,  constants  of 232 

Cigarette  papers,  composition  of 103 

—  tobacco,  nicotine  in 103 

Cigars,  nicotine  in 103 

Cinders  for  concrete 576 

Citral  in  lemon  extract 461 

orange  extract 461 

— ,  Chace  method  for 460 

— ,  f  uchsin  method  for 460 

— ,  Hiltner  method  for 461 

— ,  metaphenylenediamine  method  for    461 
Citrate-soluble  phosphate 528,  530 

—  solution,  neutral,  preparation  of. ...    525 
Clarifying  reagents  for  sugar  solutions .   398 

Clark's  scale  of  water  hardness 513 

Clay  for  paper  filler,  testing  of 318 

—  in  paper 341 

coating 344 

— ,  composition  of 318 

carrying  capacity  of  casein 316 

— ,  China    (See  also  Kaolin). 


642 


INDEX 


Clerget  formula  for  sucrose 400 

Cleveland  open  cup  flash  tester 255 

Cloth    (See  also  Fabrics,  textile). 

— ,  arsenic  in 40 

— ,  fiber  analysis  of 377 

— ,  structural  analysis  of 372 

Cloud  point    (See  Cloud  test). 

—  test  of  lubricating  oils 256 

Coal,  B.t.u.  in 176 

— ,  "H"  value  of .  .  .-.• 179 

— ,  heating  value  of 176 

— ,  nitrogen  in 183 

— ,  phosphorus  in 184 

— ,  preparation  of  laboratory    sample 

of 170,  172 

— ,  proximate  analysis  of 172 

— ,  sampling  of 167 

— ,  sulfur  in 174 

— ,  ultimate  analysis  of 180 

—  ash,  analysis  of 185 

—  refuse,  analysis  of 185 

—  tar,  crude,  analysis  of 548 

colors  in  foods 389 

products  in  soap  (reference) 288 

roofing  pitch,  analysis  of 536 

,  specifications  for 537 

Coated  paper    (See  Paper,  coated). 

Coating  on  paper,  analysis  of 343 

Cobalt  blue,  composition  of 203 

—  platinum  method  for  color  in  water  497 

Nessler  standards 500 

Cochineal  solution,  preparation  of ....  100 

Cocoa,  analysis  of 430 

— ,  artificial  coloring  matter  in 391 

—  butter,  constants  of 232,  437 

in  cocoa  and  chocolate 433 

Cocoanut  fat,  constants  of 232 

Cod  liver  oil,  elaidin  test  of 267 

,  constants  of 232 

Code  rubber,  analysis  of 480 

Coffee  beans,  artificial  coloring  in 391 

—  berry  oil,  constants  of 232 

Coke,  phosphorus  in 184 

Cold  test  of  lubricating  oils 257 

Cologne  earth  (See  Vandyke  brown). 

—  spirits    (See  Alcohol  ethyl) . 

Color  of  clay 318 

tallow 269 

ultramarine 336 

vanilla  extract 470 

water 497 

— ,  platinum-cobalt  method  for 497 

— ,  artificial,  in  clay 319. 

—  lakes,  separation  of 389 

—  test  of  nicotine 105 

sand  and  gravel 580 

Colorimetric  method  for  carbon  in  iron.  131 
iron..                                               .  513 


Colorimetric  method  for  titanium 128 

Coloring,  artificial,  in  clay 319 

—  matter  in  foods 389 

lemon  and  orange  extracts. .  .  .  463 

milk 448 

,  organic,  in  red  lead 211 

Colors,  coal-tar,  separation  of 389 

Colza  oil    (See  Rape  oil). 

Combustible  matter  in  coal  ash 185 

Combustion   apparatus   for   ultimate 

analysis 180 

—  furnace,  carbon,  (Fig.  6) 108 

,  operation  of 108,  180 

Compressor  oil,  testing  of 254 

Concentration  of  tin  ores 135 

Concrete,  analysis  of 559 

Condensed  milk    (See  Milk,  condensed). 

Confectionery,  analysis  of 409 

— ,  artificial  coloring  in 390 

"Constants"  of  oils,  fats  and  waxes. .  .  232 

Cooper,  Peter,  standard  glues 321 

Copper  as  copper  oxide,   determination 

of 119 

— ,  electrolytic,  determination  of  57, 145, 

152,  404 

—  in  aluminum  alloys 161 

Babbitt  metals 157 

Bordeaux  mixture 52 

with  Paris  green 52 

brass  and  bronze 145 

nickel  silver 152 

Paris  green 57 

solder 157 

steel 119 

— ,  thiosulf ate  method  for 58 

—  method  for  oxycellulose 368 

—  number    (See  Copper  value). 

—  potassium  chloride  solution 130 

—  reduction  methods  for  sugars 402 

—  steel,  analysis  of 116 

—  value  of  cellulose 368 

Cordage,  chemical  tests  of 382 

— ,  fibers  in 383 

— ,  sampling  of 382 

Corn  oil    (See  Maize  oil). 

Corrosive  sublimate  (See  Mercuric  chlo- 
ride). 

Cotton,  copper  value  of 368 

—  for  nitrating,  U.  S.  Navy  Specifica- 

tion for 363 

.joint     powder     specification 

for 363 

—  in  asbestos-cotton  twine 385 

cloth  and  yarns 378 

— ,  regain  of 379 

— ,  sampling  of 364 

— ,  surgical,  copper  value  of 368 

—  asbestos  twine,  analysis  of 385 


INDEX 


643 


Cotton  cellulose  for  nitration,  analysis 

of 363 

—  fibers,  stain  for 337 

—  hull  fiber,  potassium  in 43 

—  linters  for  nitration,  analysis  of ....    363 
wool  mixtures,  analysis  of 378 

—  yarn,  sizes  of 375 

Cottonseed  oil,  constants  of 232 

,  Halphen  test  for 250 

—  stearin,  constants  of 234 

Coumarin  in  vanilla  extract 468 

— ,  Hess  and  Prescott  method  for 468 

Courses  in  hosiery 376 

Cowles  method  for  malic  acid  value. .  .   427 

Crane  oil,  testing  of 254 

Crank  case  oil,  testing  of 254 

Cream,  analysis  of 449 

Creosote,  gypsy  moth,  analysis  of 536 

Croton  oil,  constants  of 234 

Crown  filler  in  paper 340,  341 

,  analysis  of 319 

Crude  fiber 393 

in  cocoa  and  chocolate 432 

Crusher  oil,  testing  of 254 

Cube   method   for  softening  point   of 

bitumens 542 

Cudbear,  dyeing  test  for 390 

Cuprammonium  silk 380 

Cuprous  oxide  method  for  nitrogen 

(reference) 67 

Curcas  oil,  constants  of 234 

Cutting  compounds,  analysis  of 486 

—  oil,  testing  of 254 

"Cutting  test"  of  casein 316 

Cyanide,  determination  of 31 

—  in  case-hardening  compounds 486 

—  method  for  formaldehyde 80 

•  nickel  in  steel 119 

—  —  —  tin  ore  assaying 136 

—  of  potash    (See  Potassium  cyanide). 

soda    (See  Sodium  cyanide). 

Cyanides,  analysis  of 31 

Cyanogen,  determination  of 31 

Cylinder  oil,  testing  of 254 

Dairy  salt,  analysis  of 24 

,  U.  S.  standard  for 24 

Dark  lubricating  oil,  testing  of 254 

Dead  oil  of  coal  tar,  analysis  of 530 

Defren-O'Sullivan  method  for  reducing 

sugars 405 

Degras,  analysis  of 274 

— ,  composition  of 274 

— ,  constants  of 234 

— ,  French 274 

Dehydration  of  tar 551 

Denaturant,  methyl  alcohol,  analysis  of  71 

— ,  nicotine,  analysis  of 103 


Denaturant,    special    No.    4,    analysis 

of ..  ... 103 

Denier  system  of  silk  numbering 375 

Density    (See  Specific  gravity). 

Dextrin,  analysis  of 91 

—  in  albumin,  detection  of 94 

honey 422 

textile  fabrics 372 

— ,  removal  of,  by  diastafor 372 

Dextrose,  Allihn  method  for 407 

—  in  dextrin 92 

honey 422 

leather 475 

— ,  Munson  and  Walker  method  for. .  .  403 
Diastafor  method   for   dextrin,    starch, 

etc 372 

Diastase  in  honey 424 

—  method  for  starch 433 

Dielectric  test  of  insulating  varnish .  .  .  229 

Dika  fat,  constants  of 234 

Dimethylglyoxime  method  for  nickel .  . 

121,  153,  162 
Dimethylparaphenylenediamine  test  for 

ground  wood 339 

Dimethylsulfate  test  for  petroleum    or 

asphalt  products  in  tar 547 

Dimethylsulfide  in  oil  of  peppermint .  .  .  465 

Disc  method  for  pulp  sampling 291 

Displacement      method      for      specific 

gravity 539,  549 

Distillation  of  carbolineum 531 

coal-tar,  crude 551 

creosote,  gypsy  moth 536 

gasoline 187 

nicotine  solution 103 

road  binders 546 

turpentine 193,  196 

water-gas  tar,  crude 551 

wood-preserving  oils 531 

Dogfish  oil,  constants  of 234 

Dolomitic  lime 324 

Dolphin  oil,  constants  of 234 

Dram  system  of  silk  numbering 375 

Dress  goods,  arsenic  in 40 

Dried  milk    (See  Milk,  dried). 
Drier,  Japan    (See  Japan  drier). 
Driers    (See  also  Drying  salts). 

—  in  paint  vehicles 206 

varnish 218,  220 

Drop  .black,  composition  of 201 

Drugs,  arsenic  in 39 

Drying  salts  in  Japan  drier 221 

—  test  for  insulating  varnish 228 

Japan  drier 223 

linseed  oil 198 

oil  varnish 220 

Ductility  test  of  bituminous  materials .  546 

Dudley  viscosity  pipette 92,  323 


644 


INDEX 


Dyeing  tests  for  artificial  colors 390 

on  paper,  comparative 307 

Dyes  for  paper  making,  testing  of 307 

—  in  foods 389 

. red  lead 211 

— ,  acid,  behavior  of 390 

— ,  aniline,  testing  of 307 

• — ,  basic,  behavior  of 390 

— ,  coal-tar,  separation  of 389 

— ,  oil-soluble,  test  for 391 

Dynamo  oil,  testing  of 254 

Egg  albumin,  analysis  of •  •  •  •  93 

—  oil,  constants  of 234 

Eggs,  analysis  of 387 

Elaidin  test  on  oils 266 

Elazy  oil,  constants  of 234 

Elderberry  oil,  constants  of 234 

Electrolytic    determination    of    ash    in 

saccharine  products 414 

cadmium 141 

copper 57,  145,  152,  404 

lead 137,  145 

zinc 146,  153,  162 

Elliott  evolution  method  for  sulfur. . .  .  132 
Elongation    (See  also  Stretch). 

Emery  test  for  beef  fat  in  lard 253 

Emulsions,  overcoming  of 261 

Enamel  paints,  analysis  of 200 

Engine  oil,  testing  of 254 

Engler  flask 187,  552 

English  scale  of  water  hardness 513 

„ —  test  on  paraffin  wax 279 

—  vermilion,  composition  of 202 

Eschka  method  for  sulfur 174 

—  mixture 175 

Esparto  fibers,  stain  for 337 

Ester  value  of  beeswax 276 

rosin 328 

Esters  in  ethyl  alcohol 74 

vinegar 457 

wood  alcohol 73 

Ether,  acid-free,  preparation  of 330 

— ,  anhydrous,  preparation  of 440 

—  extract    (See  also  Fat  and  Oil). 

of  butter 428 

cheese 453 

chocolate  and  cocoa 433 

confectionery 417 

cotton  linters '.  365 

feeds  and  grains 440 

Ethyl  acetate  in  ethyl  alcohol 74 

vinegar 457 

—  alcohol    (See  Alcohol,  ethyl). 
Evaporated  cream 449 

—  milk    (See  Milk,  evaporated) . 
Evaporation  test    (See  also  Volatility). 
of  coal-tar  roofing  pitch 537 


Evolution  method  for  sulfur 115,  132 

Expansion  coefficient  of  normal  solu- 
tions    87 

Extract,  lemon,  analysis  of 458 

— ,  orange,  analysis  of 458 

— ,  peppermint,  analysis  of 467 

— ,  spearmint,  analysis  of 467 

— ,  sumac,  analysis  of 479 

— ,  tobacco,  analysis  of 100 

— ,  wintergreen,  analysis  of 467 

— ,  vanilla,  analysis  of 468 

Extractor,  rubber  (Fig.  25) 481 

Extracts,  flavoring,  coal-tar  dyes  in ...  389 

Fabrics,  textile,  arsenic  in 40 

,  fastness  to  ironing 376 

— ,  — , light 375 

— ,  — ,  —  • —  mud  spots 376 

— ,  — , perspiration 376 

— ,  — , washing 376 

— ,  — ,  fiber  analysis  of 377 

— ,  — ,  folding  endurance  of 374 

— ,  — ,  moisture  in 377 

— ,  — ,  picks  per  inch 374 

— ,  — ,  sizing  materials  in 372,  377 

— ,  — ,  strength  of 373 

— ,  — ,  stretch  of 373 

— ,  — ,  structural  analysis  of 372 

— ,  — ,  thread  count  of 374 

— ,  — ,  weight  of 375 

— ,  — ,  weighting  in 372 

Fabris  and  Villavecchia  tests  for  sesame 

oil 252 

"Factor"  of  volumetric  solutions 6 

Factors,  gravimetric,  table  of 608 

— ,  volumetric,  table  of 615 

Fastness  tests  on  fabrics 375 

,  ultraviolet  light 375 

Fat  in  butter 428 

butter  scotch 418 

cheese 453 

• cocoa  and  chocolate 433 

condensed  or  evaporated  milk .  .  .  450 

confectionery 417 

cream 449 

cylinder  oils 259 

eggs 389 

feedstuffs 440 

grains 440 

greases 273 

leather 474 

milk 445,  446 

soap 281 

— ,  Adams  method  for 450 

— ,  Babcock  method  for 446 

— ,  Roese-Gottlieb  method  for 418,  445 

— ,  bone,  constants  of 232 

— ,  butter,  constants  of 232 


INDEX 


645 


Fat,  carapa,  constants  of 232 

— ,  chaulmoogra,  constants  of 232 

— ,  chicken,  constants  of 232 

— ,  cocoanut,  constants  of 232 

— ,  dika,  constants  of 234 

— ,  goose,  constants  of 234 

— ,  hare,  constants  of 234 

— ,  horse,  constants  of 234 

— ,  human,  constants  of 234 

— ,  lard,  constants  of 234 

— ,  laurel,  constants  of 234 

— ,  macassar,  constants  of 236 

— ,  nux  vomica,  constants  of 236 

— ,  rabbit,  constants  of 236 

— ,  sawarri,  constants  of 238 

— ,  ucuhuba,  constants  of 238 

Fats,  animal  and  vegetable,  analysis  of  230 

— ,  constants  of  (table) 232 

Fatty  acids,  constants  of  (table) 233 

,  free,  in  cutting  compounds 488 

,  — ,  —  grease 272 

,  — ,  —  soap 281 

,  Hehner  number 243 

,  insoluble,  in  oils 243 

,  — ,  volatile,  in  oils 244 

,  Polenske  number 244 

,  Reichert-Meissl  number 243 

,  soluble,  in  oils 242 

,  — ,  —  soap  (reference) 282 

,  — ,  volatile,  in  oils 243 

,  titer  test  of 246 

,  total,  in  oils 242 

,  — ,  —  soap 281 

Fatty  matter  in  soap 281 

Fatty  oil  in  sulfonated  oil 265 

Feder  aniline  chloride  test  for  invert 

sugar 424 

Feedstuffs,  analysis  of 438 

Fehling's    solutions    (Allihn    modifica- 
tion)   3,  407 

(Soxhlet  modification) 3,  403 

Ferric  chloride  reagent 3 

—  nitrate  indicator 12 

—  oxide    (See  Iron  oxide). 
Ferrocyanide,  Knublauch  method  for. .   557 
— ,  titration  of,  with  ZnSO4 557 

—  sizing  test  for  paper 354 

Ferrous    sulfate-zinc-soda    method    for 

nitrate  nitrogen 69 

Fertilizers,  analysis  of 524 

• — ,  available  organic  nitrogen  in 70 

Fiber,  crude 393 

—  (total)  in  rope  and  twines 383 

• —  analysis  of  paper 337 

• ,  standard  papers  for 339 

—  stain  for  paper  analysis .  .  .  .  • 337 

Fibers  in  cloth  and  yarns 377 

paper 337 


Fibers  in  rope  and  cordage 383 

Fiehe-Bryan  test  for  invert  sugar 423 

Filler  in  paper 340 

—  • ,  retention  of 342 

Fincke  method  for  formic  acid 457 

Fineness  test  of  clay 318 

Portland  cement. 564 

sand  and  gravel 577 

Fir-seed  oil,  constants  of 234 

Fire  point  of  carbolineum 531 

lubricating  oils 255 

wood  preserving  oils 531 

Fireproof  metal  polishes 488 

Fish,  smoked,  artificial  coloring  in 391 

—  oils  in  vegetable  oils,  test  for 254 

,  bromide  test  for 254 

Fixed  weight  system  of  yarn  sizes 374 

Flash  point  of  carbolineum 530 

lubricating  oils 255 

turpentine 218 

varnish 218 

wood  preserving  oils 530 

test    (See  Flash  point). 

tester,  Cleveland 255 

Flashing  point    (See  Flash  point). 
Flask,  distillation,  for  nicotine  analysis 

(Fig.  5) 103 

— ,  Engler 187,  552 

Flavoring  extracts,  coal-tar  dyes  in. ...  389 

Flax  fiber,  New  Zealand 384 

—  wax,  constants  of 234 

Flexibility  test  for  insulating  varnish.  .  228 

Float  test  of  bituminous  materials.  ...  541 

Flotation  test  for  grit  in  clay 318 

Foam  test  for  butter 429 

Folding  factor  of  paper 348 

—  machine,  Schopper    (Fig.  17) 348 

—  test  of  paper 347 

textile  fabrics 374 

Folio  size  of  paper 352 

Foods,  arsenic  in 35,  39 

— ,  coloring  matters  in 389 

— ,  pigments  in 389 

— ,  cattle,  analysis  of 438 

Foodstuffs,  analysis  of 387 

Formaldehyde,  cyanide  method  for. ...  80 

— ,  Hehner  test  for 78 

— ,  hydrogen  peroxide  method  for 79 

— ,  Leach  test  for 78 

— ,  morphine  sulf ate  test  for 78 

—  solutions,  analysis  of 79 

—  test  for  casein 344 

sesame  oil 253 

Formic  acid,  analysis  of 81 

in  vinegar 457 

,  Fincke  method  for 457 

,  permanganate  method  for 81 

Fractionation    (See  Distillation). 


646 


INDEX 


Freezing  mixtures 257 

French  degrees  of  water  hardness 513 

Froth  oil,  testing  of 254 

Fruit  juices,  coal-tar  dyes  in 389 

Fruits,  canned,  coal-tar  dyes  in 391 

— ,  preserved,  coal-tar  dyes  in 391 

Fuchsin  method  for  aldehydes 75 

— . citral 460 

—  nitrite  standards.  .  . 505 

Fuels,  liquid,  analysis  of 190 

Fuller's    earth    as    a    water     turbidity 

standard 494 

Fuming  nitric  acid     (See  Nitric  acid, 
red  fuming). 

—  sulf uric  acid    (See  Oleum) . 

Furfural  in  ethyl  alcohol 76 

— ,  phloroglucid  method  for 366 

—  test  for  sesame  oil 252 

—  value  of  cellulose 366 

• cotton  linters 366 

Furnace,  combustion  carbon 108,  180 

Fusel  oil  in  ethyl  alcohol 77 

,  permanganate  method  for 77 

Galactan  in  feedstuffs  and  grain  (refer- 
ence)    442 

Galactose,  Allihn  method  for 408 

Gallon,  grains  per  U.  S 515 

Galvanizing  on  iron  and  steel 163 

—  test,  Preece  method 164 

Garden  cress  oil,  constants  of 234 

—  rocket  oil,  constants  of 234 

Gas  black,  composition  of 201 

—  engine  oil,  testing  of 254 

Gasoline  in  soap 286 

— ,  analysis  of 185 

— ,  desirable  properties  of 185 

— ,  types  of 186 

—  test  on  cylinder  oils 260 

Gauze,  corrosive  sublimate  in 62 

Gear  grease 271 

Gelatin  in  albumin,  qualitative  test  for .  94 
milk,  qualitative  test  for 448 

—  silk 380 

German  degrees  of  water  hardness.  .  . .  513 

—  silver    (See  Nickel  silver) . 
Ghedda  wax    (See  Indian  beeswax). 
Gillmore    needles    for    cement    testing 

(Fig.  28b) 568 

Glucose  by  polarization  at  87°  C 416 

—  in  honey 423 

leather 475 

• saccharine  products 416 

• syrups 416 

— ,  qualitative  test  for 423 

Glue,  analysis  of 320 

—  in  albumen,  qualitative  test  for ....      94 

344,  355,  356 


Glue,   in  the   presence  of  starch,  test 

for 356 

— ,  Peter  Cooper  standard 321 

— ,  qualitative  test  for 94,   355 

— ,  tannin  test  for 94,  355 

Glycerine    (See  also  Glycerol). 

— ,  analysis  of 85 

—  jacketed  drying  oven 173 

—  soap 286 

Glycerol,  acetin  method  for 85 

— ,  bichromate  method  for 89,   285 

— ,  determination  of 85 

—  in  lemon  extract 459 

orange  extract 459 

the  presence  of  sugar 285 

soap 285 

lyes 85 

vanilla  extract '. 473 

vinegar  (reference) 454 

potash  saponification 247 

Glyoxime  method  for  nickel.  .121,   153,  162 
Golden  ochre,  composition  of 203 

—  sulfide  of  antimony 34 

Goose  fat,  constants  of 234 

Gottlieb-Roese  method  for  fat.  .  .  .418,  445 

Governor  oil,  testing  of 254 

"Grab  method"  for  tensile  strength...  .    37 

Grain  alcohol    (See  Alcohol  ethyl). 

Grains,  mixed,  analysis  of 438 

—  per  U.  S.  gallon 515 

U.  S.  gallon  to  pounds  per  10,000 

gallons 515 

Grams  per  square  inches  to  ounces  per 

square  yard,  factor  for 375 

Grapeseed  oil,  constants  of 234 

Graphite,  composition  of 201 

—  in  greases 273 

—  grease • 271 

Graphitic  carbon  in  iron 131 

steel 110 

Gravel,  color  test  of 580 

— ,  mechanical  testing  of 576 

— ,  organic  matter  in 580 

—  for  concrete 576 

—  in  mortar  and  concrete 559 

Gravimetric  factors,  table  of 608 

Gravity    (See  also  Specific  gravity). 

—  of  oils 230,  254 

—  Baum6  and  specific  gravity,  relation 

of 255 

Gray  acetate    (See  Calcium  acetate). 

Grease  in  glue 323 

Greases,  analysis'  of 270 

— ,  types  of 270 

Green  pigments,  classification  of 203 

—  pole  painj,  analysis  of 207 

Grinding  mill  for  feedstuffs 438 

Grit  in  clay  or  kaolin 318 


INDEX 


647. 


Grit  in  talc 335 

— ,  flotation  test  for 318 

— ,  sieve  test  for 318 

Ground  wood,  qualitative  tests  for.  .  .  .    338 

pulp  fibers,  stain  for 337 

Gums  in  albumin,  detection  of 93 

varnish 219 

— ,  Boughton  method  for  (reference) .  .    217 

Gunning  method  for  nitrogen 65 

,  modified  for  nitrates 67 

Gutzeit-Sanger-Black   method    for    ar- 
senic        37 

Gypsum  in  talc 335 

— ,  analysis  of 319 

— ,  composition  of 201 

— ,  burnt,  composition  of 201 

Gypsy  moth  creosote,  analysis  of 536 

"  H  "  value  of  coal 179 

Haddock  oil,  constants  of 234 

Halphen  test  for  cottonseed  oil 250 

Harder  and  Abrams  color  test  for  sand .    580 

Hardness  of  water 510 

— ,  Clark's  scale 513 

— ,  English  degrees 513 

— ,  French  degrees 513 

,  German  degrees 513 

— ,  permanent 511 

,  soap  method  for 511 

,  temporary 511 

Hare  fat,  constants  of 234 

Hazelnut  oil,  constants  of 234 

Heating  test  of  tung  oil 199 

—  value  of  benzole  acid 178 

coal 176 

—  liquid  fuels 190 

—  naphthalene 178 

Hedges'  method  for  arsenious  oxide .  .  .     .56 
Hehner  number  of  oils 243 

—  test  for  formaldehyde 78 

—  value    (See  Hehner  number). 

Hemp  fibers,  stain  for 337 

Hempel  column  (Fig.  11) 193 

Hempseed  oil,  constants  of 234 

,  elaidin  test  of 267 

Herle's  solution  for  clarifying 399 

Herring  oil,  constants  of 234 

Herzfeld  formula  for  sucrose  and   rafn- 

nose 401 

Hess  and  Prescott  method  for  coumar- 

in  and  vanillin 468 

Hide  substance  in  leather 475 

Hiltner  method  for  citral 461 

Honey,  analysis  of 420 

— ,  artificial 424 

- — ,  mineral  adulterants  in 414 

Home  method  for  clarifying  sugar  solu- 
tions     399 


Horse  fat,  constants  of 234 

—  marrow,  constants  of 234 

—  oil,  constants  of 234 

Horsefoot  oil,  constants  of 234 

Hortvet  and  West  method  for  methyl 

salicylate  in  wintergreen  extract.  .  .  .  468 

Hosiery,  testing  of 376 

Howard  method  for  essential  oil  in  mint 

and  wintergreen  extracts 467 

Hubbard  pycnometer  method  for 

specific  gravity 538,  550 

Human  fat,  constants  of 234 

Hydrocarbons,  non-volatile,  in  soap .  .  .  287 

— ,  volatile,  in  soap 286 

Hydrocellulose,  caustic  method  for ....  365 

—  in  cellulose 365 

cotton  linters 365 

Hydrochloric  acid  (See  also  Chlorides) . 

in  formic  acid 81 

reagent 3 

,  volumetric  solutions  of 7,  8 

Hydrocyanic  acid    (See  also  Cyanides). 

Hydrogen  in  coal 182 

—  peroxide    (See  also  Peroxide). 

method  for  formaldehyde 79 

Hydrometer  method  for  specific  gravity 

410,  538 

Hydrosulfite    (See  also  Sodium  hydro- 
sulfite) 

—  method  for  indigotin 97 

Hydroxide,  qualitative  test  for 20 

Hypochlorite  of  lime    (See  Bleach). 
Hyposulfite    (See  Thiosulf ate) . 

Ignition  loss  of  cement 572 

lime 325 

—  talc 334 

Incrusting  solids  in  water 520 

Index    of   refraction      (See    Refractive 

index) . 
Indian  beeswax 277 

—  red,  composition  of 202 

Indicators,  preparation  of 12 

Indigo,  analysis  of 97 

— ,  natural,  impurities  in 97 

— ,  sulfonation  of 98 

— ,  synthetic 97 

—  carmine  solution,  preparation  of ....      96 

Indigotin  in  indigo 97 

— ,  hydrosulfite  method  for 97 

Ink,  standard  iron  tannate 354 

—  sizing  test  of  papers 354,  358 

Insoluble  residue  in  cement 573 

Insulating  compound,  rubber  (See  Rub- 
ber). 

—  varnish     (See  Varnish,  insulating) . 
Insulation,  asbestos-magnesia,  analysis  of  62 
Inversion  of  sugar  solutions 400 


648 


INDEX 


Invert  sugar    (See  Sugar,  invert). 

Iodides    (See  also  Iodine) . 

Iodine,  0.1  N  solution  of 10 

—  jelly  test  of  tung  oil 199 

—  number  of  oils 241 

rosin 225 

shellac 225 

,  Wijs  method  for 225,  241 

—  value    (See  Iodine  number). 
Iron    (See  also  Iron  oxide). 

— ,  analysis  of 129 

—  in  alkalies , 22 

aluminum  alloys 162 

sulf ate 304 

brass  and  bronze 148 

water 513,517 

zinc 139 

— ,  Jones  reductor  method  for 148 

— ,  sampling  of 106,   129 

— ,   sulfocyanate    colorimetric    method 

for 513 

— ,  cast,  analysis  of 129 

— ,  charcoal,  analysis  of 129 

— ,  galvanized,  testing  of 163 

— ,  pig,  analysis  of 129 

— ,  sheradized,  testing  of 163 

— ,  tinned,  testing  of 166 

—  oxide  in  aluminum  sulf  ate 304 

blanc  fixe.. 310 

boiler  scale 523 

chrome  yellow 215 

green  pole  paint 209 

Portland  cement 574 

presence  of  phosphates 25 

salt 25 

talc 334 

water 517 

and  alumina  in  lime 325 

Ironing  test  on  textile  fabrics 376 

Istle  fiber    (See  Tampico). 

Ivory  black,  composition  of .  , 201 

Jamba  oil,  constants  of 234 

Jams,  analysis  of 409 

— ,  artificial  coloring  in 390 

Japan  drier,  analysis  of 221 

,  P.  &  R.  R.  R.  specifications  for.  222 

,  U.  S.  Navy  specifications  for.  .  .  222 

—  wax,  constants  of 234 

Japanese  wood  oil  (See  also  Tung  oil) . 

,  constants  of 234 

Javillier  and  Bertrand  method  for  nico- 
tine   101 

Jean  method  for  free  acid  in  leather ....  476 

Jelly,  analysis  of 409 

— ,  artificial  coloring  in 390 

—  test'of  glue 321 

tung  oil 199 


Jones  reductor,  use  of 148 

Journal  grease,  analysis  of 270 

—  oil,  testing  of 254 

Juices,  fruit,  coal-tar  dyes  in 389 

Jute  fibers,  stain  for 337 

Kainite,  potash  in 41 

Kaolin,  composition  of 201 

—  for  paper  filler,  testing  of 318 

Kapok  oil,  constants  of 234 

Kennedy  method  for  crude  fiber 394 

Ketones  in  crude  wood  alcohol  (refer- 
ence)    371 

Kissling  method  for  nicotine 100 

Kjeldahl  method  for  nitrogen 64 

— ,  modified  for  nitrates 67 

Gunning- Arnold  method  for  nitro- 
gen   66 

Knublauch  method  for  ferrocyanide. .  .  .  557 

Koeme  oil,  constants  of 234 

Koettstorfer  number 241 

—  value    (See  Koettstorfer  number). 

Kokum  butter,  constants  of 234 

Kraft  pulp    (See  Sulf  ate  pulp). 

Lactic  acid  in  cheese 452 

Lactose  in  cocoa  and  chocolate. . .  .403,  434 

condensed  or  evaporated  milk .  .  .  450 

milk 445 

— ,  Defren-O'Sullivan  method  for 405 

— ,  Munsen  and  Walker  method  for ...  408 

Lakes,  composition  of 202 

—  in  foods 389 

Lallamantia  oil,  constants  of 234 

Lampblack,  composition  of 201 

Lard,  Emery  test  for  beef  fat  in 253 

—  fat,  constants  of 234 

—  oil,  analysis  of 265 

,  constants  of 234 

,  grades  of 265 

Laurel  fat,  constants  of 234 

Leach  method  for  coloring  matter  in 

milk 448 

—  test  for  formaldehyde 78 

Lead  in  aluminum  alloys 161 

Babbitt  metals 157 

blanc  fixe,  qualitative  test  for .  .  .    309 

Bordeaux  mixture  and  lead  arsen- 

ate 54 

brass  and  bronze 145 

chrome  yellow 215 

greases 272 

green  paint 208 

Japan  drier 221 

nickel  silver 153 

red  lead 210 

solder 156 

type  metals 159 


INDEX 


649 


Lead  in  white  lead. 
metals .  .  . 


212 

156 

zinc 137 

— ,  chromate  method  for 47,  208,  212 

— ,  electrolytic  method  for 137,  145 

— ,  lead  acid  method  for 138 

— ,  sulfate  method  for.  .  .  138,  145,  156,  214 

— ,  red,  analysis  of 210 

,  composition  of 202 

— ,  white,  analysis  of 211 

,  composition  of 201,  211 

—  acetate  in  white  lead 213 

,  dry  basic,  as  clarifier 399 

reagent 4,  399 

solution,  basic 4,  90,  399 

—  acid,  preparation  of 138 

method  for  lead 138 

—  arsenate,  analysis  of 46 

,  composition  of 46 

with  Bordeaux  mixture,  analysis 

of 54 

—  carbonate,  basic   (See  White  lead) . 

—  chromate  in  chrome  yellow 215 

green  paint 208 

,  scarlet,  composition  of 202 

—  nitrate  solution,  basic 399 

—  number  of  maple  products 426 

vanilla  extract 470 

,  Winton  method  for. 426 

—  oxide    (See  also  Lead). 

in  Bordeaux   mixture  with  lead 

arsenate 54 

lead  arsenate 47 

red  lead 210 

,  water  soluble,  in  lead  arsenate .  .  49 

—  precipitate  test  for  vinegar 455 

—  soap  in  greases 272 

—  sulfate  in  blanc  fixe 310 

Leather,  analysis  of 474 

— ,  chromium  in 477 

Lehner  silk 379 

Lemon  chrome  yellow,  composition  of. .  202 

—  extract,  analysis  of 458 

—  oil,  analysis  of 464 

in  lemon  extract 460 

—  peel  color,  Albrech  test  for 463 

Levol  method  for  tin  ore  assaying 136 

Levulose  in  honey 422 

— ,  Allihn  method  for 408 

Lichen  colors,  behavior  on  wool 390 

Liebermann-Storch  test  for  rosin.  .219,  356 

Light,  fastness  of  fabrics  to 375 

Lime    (See  also  Calcium  oxide) 

— ,  analysis  of 324 

— ,  classification  of 324 

—  in  aluminum  sulfate 305 

blanc  fixe 310 

boiler  scale.  ..                                  .  523 


Lime  in  concrete 560 

lime 325 

lime-sulfur  solution 61 

mortar 560 

Portland  cement 575 

salt 26 

satin  white 333 

sulfite  acid 301 

water 518 

— ,  specifications  for 324 

— ,  volumetric    permanganate    method 

for 326,  518 

— ,  acetate  of    (See  Calcium  acetate). 

— ,  dolomitic 324 

— ,  hydrated,  grades  of 324 

— ,  — ,  specifications  for 324 

sulfur  solution,  analysis  of 59 

—  water  reagent 3 

—  and  magnesia,  sulfate  method  for .  .    301 

Limestone,  analysis  of 327 

Limonite,  composition  of 202 

Lindo-Gladding  method  for  potassium      41 
Linen  fibers,  stain  for 337 

—  yarn,  sizes  of 375 

Linotype  metals,  analysis  of 158 

Linseed  oil,  analysis  of 197 

,  constants  of 197,  234 

,  drying  test  of 198 

,  elaidin  test  of 266 

,  boiled 197 

,  raw 197 

Linters,  cotton,  analysis  of 363 

Liquors,  distilled,  coal-tar  dyes  in 389 

Litharge    (See  Lead  oxide). 

Lithopone,  composition  of 201 

Litmus,  dyeing  test  for 390 

Loading  in  paper    (See  Filler). 

Loew's  reagent  for  silk 381 

Loewenthal-Proctor  method  for  tannin 

95,  479 

" Long  oil"  varnish 220 

Loom  oil,  testing  of 254 

Lubricating  oils,  testing  of 254 

Lustron  silk : 380 

Macassar  fat,  constants  of 236 

Machine  oil,  testing  of 254 

Machinery  oil,  testing  of 254 

Madia  oil,  constants  of 236 

Mafura  tallow,  constants  of 236 

Magnesia  in  asbestos-magnesia    cover- 
ing   62 

blanc  fixe 310 

boiler  scale 523 

lime 324,  326 

mortar  and  concrete 560 

paper  ash 341 

Portland  cement .  .                          .  575 


650 


INDEX 


Magnesia  in  salt 26 

sulfite  acid 301 

water 518 

—  and  lime,  sulfate  method  for 301 

—  asbestos  pipe  covering,  analysis  of .  .  62 
,  composition  of 62 

—  lime 324 

—  method  for  ammoniacal  nitrogen ...  68 

—  mixture  for  phosphates  in  fertilizers .  526 
reagent 4 

—  wash  solution 4,  518 

Magnesium  in  aluminum  alloys 162 

—  ammonium  chloride  solution      (See 

Magnesia  mixture). 

—  carbonate  in  asbestos,  magnesia  cov- 

ering    63 

—  oxide    (See  Magnesia) . 

—  sulfate,  separation  from  calcium  sul- 
fate   301 

Maize  oil,  constants  of 236 

Malabar  tallow,  constants  of 236 

Malic  acid  in  vinegar. 456 

value  of  maple  products,  Cowles 

method 427 

Malt  extract,  preparation  of 433 

Maltose,  Munson  and  Walker  method 

for 408 

Manganese,    bismuthate    method     for 

110,  147,  161 

— ,  chlorate  method  for 148 

—  in  alloy  steel 116 

aluminum  alloys 161 

brass  and  bronze 147 

high  chrome  steels 116 

iron 131 

Japan  drier 222 

steel 110 

Manihot  oil,  constants  of 236 

Manila  fibers,  stain  for 337,  383 

,  Swett  test  for 383 

—  and  sisal  fibers,  distinction  between .  383 
Maple  cream,  analysis  of 425 

—  products,  analysis  of 424 

—  sugar,  analysis  of 425 

—  syrup,  analysis  of 424 

Margarine 427 

Marine  animal  oils,  bromine  test  for. .  .  254 

Marrow,  beef,  constants  of 232 

— ,  horse,  constants  of 234 

Marsh  reagent  for  testing  vanilla 471 

—  test  for  arsenic 36 

Massecuites,  analysis  of 409 

Maumene  test  on  oils 267 

Mechanical  moisture  in  crown  filler ....  319 

—  testing  of  sand  and  gravel  for  con- 

crete   576 

Melting  point   (See  also  Softening  point) . 
,  closed  capillary  tube  method  for.  245 


Melting  point,  drop  method  for 276 

of  beeswax 276 

—  fats  and  oils 245 

greases 271 

paraffin  wax 278 

tallow 269 

,  open  tube  method  for 271,  278 

,  titer  test 246 

,  Wiley  method  for  (reference)  ...  246 

Menhaden  oil,  constants  of 236 

Menthol  in  oil  of  peppermint 465 

— ,  structure  of 466 

Menthyl  acetate  in  oil  of  peppermint.  .  465 

Mercuric  bromide  paper  for  arsenic  test.  37 

—  chloride  in  gauze 62 

reagent 4 

Alercury  in  zinc  amalgam 163 

— ,  sulfide  method  for 62 

Messinger  method  for  acetone 72 

Metal  polishes,  analysis  of 488 

Metals,  type,  analysis  of 158 

— ,  white,  analysis  of 154 

Methyl  acetate  in  wood  alcohol 73 

—  alcohol  (denaturant) ,  analysis  of  ...  71 

in  grain  alcohol 78 

lemon  extract 462 

orange  extract 462 

wood  distillate  (reference) ....  370 

,  methyl  violet  test  for 462 

,  qualitative  tests  for 78,  462 

,  Riche  and  Bardy  test  for 462 

—  orange  indicator 12 

—  red  indicator 12 

—  salicylate  in  wintergreen  extract. .  .  .  468 

—  violet  test  for  methyl  alcohol 462 

Milk,  analysis  of .* 443 

— ,  composition  of 443 

— ,  standard 443 

—  chocolate,  analysis  of 430 

— ,  condensed,  analysis  of 449 

— ,  — ,  standard 449 

— ,  evaporated,  analysis  of 449 

—  fat  in  milk  chocolate 437 

— ,  skimmed,  standard 443 

—  solids,  composition  of 438,  443 

in  condensed  milk 451 

• milk  chocolate 437 

—  sugar    (See  Lactose) . 

"  Mill  test"  of  sulfite  acid 302 

'Mineral  acid  in  oils 260 

,  free,  in  leather 475 

—  matter    (See  also  Ash). 

in  greases 273,  274 

—  oil  in  creosote,  etc.    (See  Sulfonation 

residue). 

fatty  oil  mixtures 261 

grease 274 

paint  vehicle .  206 


INDEX 


651 


Mineral  oil  in  sulfonated  oils 264 

—  weighting  of  textile  fabrics .  372 

Mitchell  method  for  lemon  and  orange 

oils 460 

Mohr's  alkalimeter  for  carbon  dioxide .  .  212 
Moisture  by  drying  in  vacuo    without 

heat 224 

upon  asbestos 452 

pumice  stone 409 

quartz  sand 410,  425 

—  in  acetate  of  lime 32 

albumin 94 

alkalies 20 

ammonium  sulfate 525 

asbestos  cotton  twine 386 

asphalt  road  binders 538 

bicarbonates 20 

bituminous  road  binders 538 

blanc  fixe 309 

Bordeaux  mixture 50 

butter 428 

calcium  sulfate,  hydrated 319 

case-hardening-compounds 484 

casein 315 

cheese 452 

chocolate  and  cocoa 430 

clay 318 

coal 172,  173 

coal  ashes 185 

condensed  or  evaporated  milk .  .  .  450 

cotton  linters 364 

—  crown  filler 319 

cutting  compounds 486 

dextrin 91 

feedstuff s  and  grains 438 

fertilizers • 525 

glue 320 

greases 271 

—  honey 420 

indigo 97 

lead  arsenate 47 

leather 474 

maple  sugar  and  syrup 425 

massecuites 409 

molasses 409 

Paris  green 55 

—  potash  salts 525 

potassium  carbonate 20 

pulp 293 

road  binders 538 

rope  and  twine 382 

rosin  size : 330 

—  saccharine  products 409 

satin  white 333 

shellac 224 

soap 280 

soda  ash 20 

sodium  bicarbonate.  ..  20 


Moisture  in  sodium  nitrate 525 

silicate 29 

spent  oxide 555 

sugar 409 

sulfonated  oils 264 

sulfur 17 

syrups .- 409 

—  tallow,  qualitative  test  for 270 

tar 550 

textile  fabrics 377 

water  glass 29 

wood  pulp 293 

— ,  xylol  method  for 27f 

Molasses,  analysis  of 409 

— ,  mineral  adulterants  of 414 

Molecular  weights,  table  of 586 

Molybdate  method  for  phosphates.525,  528 
; phosphorus 112,  114,  143 

—  solution     (See  Ammonium  molyb- 

date  solution). 

Molybdenum  in  steel 127 

— ,  lead  molybdate  method  for 127 

— ,  qualitative  test  for 127 

—  steel,  analysis  of 116 

Monotype  metal,  analysis  of 158 

Morphine  sulfate  test  for  formaldehyde  78 

Mortar,  analysis  of 559 

— ,  cement,  preparation  of 565 

— ,  standard  1:3 567 

Mowrah  seed  oil,  constants  of 236 

Mud  spot  test  of  textile  fabrics 376 

Mullen  test  of  paper      (See  Bursting 

strength) . 

—  tester  for  paper,  Perkins  (Fig.  18) .  .  349 
Munson  and  Walker  method  for  reduc- 
ing sugars 403 

Mustard  oil,  constants  of 236 

Mutton  tallow,  analysis  of 268 

-,  constants  of 236,  269 

Myrtle  wax,  constants  of 236 

Naphtha,  crude 186 

—  in  soap 286 

metal  polishes 488 

Naphthalene,  heating  value  of 178 

Naphthol  green  B,  behavior  on  dyeing.  390 

a-Naphthol  test  for  sucrose 417 

a-Naphthylamine  acetate    reagent    for 

nitrites 504 

Neatsfoot  oil,  constants  of 236 

Needle,  standard  Roberts,  for  penetra- 
tion test 539 

Nessler  standards,  platinum-cobalt. . .  .  500 

Nessler's  reagent '.  .  .  .  388,  499 

Nesslerization  method  for  ammonia .  .  .  501 

New  York- Liverpool  test  of  alkalies.  .  .  21 

New  Zealand  flax  fiber 383,  384 

Newcastle  test  of  alkalies .  .  21 


652 


INDEX 


Nickel,  cyanide  method  for 119 

— ,  dimethylglyoxime       method         for 

121,  153,  162 

— ,  hydroxide  method  for 151 

—  in  aluminum  alloys 162 

brass  and  bronze 151 

nickel  silver 153 

steel 119 

—  silver,  analysis  of 152 

—  steel,  analysis  of 116 

Nicotine,  Bertrand  and  Javillier  method 

for 101 

'• —  in  tobacco  and  extracts 100 

— ,  Kissling  method  for 100 

— ,  silicotungstate  method  for 101 

—  flask  (Fig.  5) 104 

—  solution  (denaturant),  analysis  of 103 

Niger  seed  oil,  constants  of 236 

Nitrates,  absolute  (CuO)    method  for 

(reference) 67 

• — ,  ferrous  sulfate-zinc-soda  method  for  69 

— ,  Gunning  method  for 67 

—  in  ethyl  alcohol 79 

fertilizers 525 

sewage 507 

water,  phenolsulfonic  acid  meth- 
od for 505 

,  reduction  method  for 507 

— ,  Kjeldahl  method  for 67 

— ,  nitrogen  in 69 

— ,  phenolsulfonic  acid  test  for 79 

— ,  qualitative  test  for 525 

— ,  Ulsch-Street  method  for 68 

— ,  zinc-iron  method  for 68 

Nitration,  analysis  of  cotton  for 363 

Nitric  acid  reagent 4 

,  red  fuming 4 

test  for  ground  wood 339 

Nitrite  of  soda    (See  Sodium  nitrite). 

Nitrites,  fuchsin  standards  for 505 

—  in  water  and  sewage 504 

— ,  titration  of 28 

Nitrogen,  absolute  method  for   (refer- 
ence)    67 

— ,  azotometer  method  for  (reference) . .  67 

— ,  cuprous  oxide  method  for  (refer- 
ence)    67 

— ,  ferrous  sulfate-zinc-soda  method 

for ?...  69 

— ,  Gunning  method  for 65 

—  in  case-hardening  compounds 485 

coal 183 

f eedstuffs  and  grains 439 

fertilizers 64,  70,  525 

leather 475 

nitrate  salts 68,  69 

organic  matter 64 

sewage 498 


Nitrogen  in  water 498 

— ,  Kjeldahl  method  for 64 

Gunning- Arnold  method  for 66 

— ,  magnesia  method  for 68 

— ,  Ulsch-Street  method  for 68 

— ,  zinc-iron  method  for 68 

— ,  albuminoid 439,  502 

— ,  — ,  in  feeds 439 

— ,  — ,  —  water 502 

— ,  —  ammoniacal  in  water 502 

— ,  amido 440 

— ,  ammoniacal,  in  sewage 501 

— ,  — ,  —  water 498 

— ,  — ,  magnesia  method  for 68 

— ,  —  and  nitric 68 

— ,  nitrate,  in  sewage  and  water 505 

— ,  nitric  and  ammoniacal 68 

— ,  —  and  organic 67 

— ,  nitrite,  in  sewage  and  water 504 

— ,  organic 64,  69 

— ,  — ,  available 69 

— ,  — ,  total,  in  sewage  and  water  ....  503 

— ,  —  and  nitric 67 

— ,  — ,  total 67 

Normal  consistency  of  cement 566 

—  solutions,    temperature    corrections 

for 13 

,  —  expansion  coefficient  of 87 

Nut  oil    (See  Tung  oil). 

Nutmeg  butter,  constants  of 236 

Nux  vomica  fat,  constants  of 236 

Ocher,  golden,  composition  of 203 

Ochers,  composition  of 202 

Odor  of  water 493 

Oil  in  boiler  scale 522 

cotton  linters 365 

cutting  compounds 487 

leather 474 

paints 204,  206 

paraffin  wax 279 

rope  and  twine 382 

sulf onated  oil 264 

white  lead 211 

— ,  unsaponifiable  matter  in 261 

— ,  acorn,  constants  of 232 

— ,  air  compressor,  testing  of 254 

— ,  almond,  constants  of 232 

— ,  anchovy,  constants  of 232 

— ,  apricot  kernel,  constants  of 232 

— ,  arachis    (See  Peanut  oil). 

— ,  automobile,  testing  of 254 

• — ,  bear,  constants  of 232 

— ,  beechnut,  constants  of 232 

— ,  ben,  constants  of 232 

— ,  black,  testing  of 254 

— ,  bone,  constants  of 232 

— ,  bottlenose,  constants  of 232 


INDEX 


653 


Oil,  Brazilnut,  constants  of 232 

— ,  calender,  testing  of 254 

— ,  calophyllum,  constants  of "232 

— ,  cameline,  constants  of 232 

— ,  canari,  constants  of 232 

— ,  candlenut,  constants  of 232 

— ,  carbolineum,  analysis  of 530 

— ,  castor,  analysis  of 263 

— ,  — ,  constants  of 232,  263 

— ,  cedar  nut,  constants  of 232 

— ,  cherry  kernel,  constants  of 232 

— ,  —  laurel,  constants  of 232 

— ,  China  wood    (See  Tung  oil). 

— ,  chrysalis,  constants  of 232 

— ,  — ,  Japanese,  constants  of 232 

— ,  codliver,  constants  of 232 

— ,  — ,  elaidin  test  of 267 

— ,  coffee  berry,  constants  of 232 

— ,  colza    (See  Rape  oil). 

— ,  compressor,  testing  of 254 

• — ,  corn    (See  Maize  oil). 

— ,  cottonseed,  constants  of 232 

— ,  — ,  Halphen  test  for 250 

— ,  crane,  testing  of 254 

— ,  crank  case,  testing  of 254 

— ,  creosote,  analysis  of 536 

— ,  croton,  constants  of 234 

— ,  crusher,  testing  of 254 

— ,  curcas,  constants  of 234 

— ,  cutting,  testing  of 254 

— ,  cylinder,  testing  of 254 

— ,  dark  lubricating,  testing  of 254 

— ,  dogfish,  constants  of 234 

— ,  dolphin,  constants  of 234 

— ,  dynamo,  testing  of .  254 

— ,  egg,  constants  of 234 

— ,  elderberry,  constants  of 234 

— ,  elazy,  constants  of 234 

• — ,  engine,  testing  of 254 

— ,  firseed,  constants  of 234 

— ,  fish,  test  for 254 

— ,  froth,  testing  of 254 

— ,  fusel,  in  ethyl  alcohol 77 

— ,  garden  cress,  constants  of 234 

— ,  —  rocket,  constants  of 234 

— ,  gas  engine,  testing  of 254 

— ,  governor,  testing  of 254 

— ,  grapeseed,  constants  of 234 

— ,  haddock,  constants  of 234 

— ,  hazelnut,  constants  of 234 

• — ,  hempseed,  constants  of 234 

— ,  — ,  elaidin  test  of 267 

— ,  herring,  constants  of 234 

— ,  horse,  constants  of 234 

— ,  horsefoot,  constants  of 234 

— ,  jamba,  constants  of 234 

— ,  Japanese  wood  (See  also  Tung  oil) . 

— , ,  constants  of 234 


Oil,  journal,  testing  of 254 

— ,  kapok,  constants  of 234 

— •,  koeme,  constants  of 234 

— ,  lallamantia,  constants  of 234 

— ,  lard,  analysis 265 

— ,  — ,  constants  of 234 

— ,  — ,  grades  of 265 

— ,  lemon,  analysis  of 464 

— ,  — ,  in  lemon  extract 460 

— ,  linseed,  analysis  of 197 

— ,  — ,  constants  of 197,  234 

— ,  — ,  drying  test  of 198 

— ,  — ,  elaidin  test  of 267 

• — ,  loom,  testing  of 254 

— ,  lubricating,  testing  of 254 

— ,  machine,  testing  of 254 

— ,  madia,  constants  of 236 

— ,  maize,  constants  of 236 

— ,  manihot,  constants  of 236 

— ,  menhaden,  constants  of 236 

— ,  mineral,  in  creosote,  etc.    (See  Sul- 
f  onation  residue) . 

— ,  — ,  —  fatty  oil  mixtures 261 

— ,  — ,  —  grease 274 

— ,  — ,  —  sulf onated  oil 264 

— ,  mowrah  seed,  constants  of 236 

— ,  mustard,  constants  of 236 

— ,  neatsf oot,  constants  of 236 

— ,  niger  seed,  constants  of 236 

— ,  nut    (See  Tung  oil). 

— ,  olive,  analysis  of 266 

— ,  — ,  constants  of 236,  266 

— .  — ,  elaidin  test  of, 267 

— ,  —  kernel,  constants  of 236 

— -,  orange,  analysis  of 464 

— ,  — ,  in  orange  extract 464 

— ,  ostrich,  constants  of 236 

— ,  owala,  constants  of 236 

— ,  palm,  constants  of .  236 

• — ,  —  nut,  constants  of 236 

— ,  peach  kernel,  constants  of 236 

— ,  peanut,  constants  of 232 

— ,  — ,  elaidin  test  of 267 

— ,  — ,  tests  for 250 

— ,  peppermint,  analysis  of 464 

— ,  — ,  in  peppermint  extract 467 

— ,  perilla,  constants  of 236 

— ,  persimmon  seed,  constants  of 236 

• — ,  pistachio  nut,  constants  of 236 

— ,  plum  kernel,  constants  of 236 

— ,  poppy  seed,  constants  of 236 

— ,  porpoise,  constants  of 236 

— ,  porpoise  jaw,  constants  of 236 

— ,  pumpkin  seed,  constants  of 236 

— ,  quince,  constants  of 236 

— ,  radish  seed,  constants  of 236 

— ,  rape,  constants  of 238 

— ,  — ,  elaidin  test  of 267 


654 


INDEX 


Oil,  rape,  Maumene  test  of 268 

— ,  ravison,  constants  of 238 

— ,  red,  constants  of 238 

— ,  rice,  constants  of 238 

— ,  rosin,  constants  of 238 

— ,  — ,  test  for 249 

— ,  saffron,  constants  of 238 

—.salad 266 

— ,  salmon,  constants  of 238 

— ,  sanguinella,  constants  of 238 

— ,  sardine,  constants  of 238 

— ,  seal,  constants  of 238 

— ,  senega  root,  constants  of 238 

±—t  sesame,  constants  of 238 

— ,  — ,  elaidin  test  of 267 

— ,  — ,  tests  for 252 

— ,  shafting,  testing  of 254 

— ,  shark,  constants  of 238 

— ,  sheepsfoot,  constants  of 238 

— ,  — ,  elaidin  test 267 

— ,  skunk,  constants  of 238 

— ,  sod    (See  also  Degras). 

— ,  soja  bean,  constants  of 238 

— ,  spearmint,  in  spearmint  extract .  .  .  467 

— ,  sperm,  constants  of 238 

— ,  — ,  testing  of 254 

— ,  spermaceti,  constants  of 238 

— ,  spindle,  testing  of 254 

— ,  sterculia,  constants  of 238 

— ,  sturgeon,  constants  of 238 

— ,  sulfonated,  analysis  of 263 

— ,  sunflower,  constants  of 238 

— ,  table :..  266 

— ,  tallow,  constants  of 238 

— ,  tallowseed,  constants  of 238 

— ,  tea  seed,  constants  of 238 

— ,  tobacco  seed,  constants  of 238 

— ,  transformer,  testing  of 254 

— ,  tung,  analysis  of 198 

— ,  — ,  constants  of 232 

— ,  turbine,  testing  of 254 

— ,  turkey  red,  analysis  of 263 

— , ,  constants  of 238 

— ,  turtle,  constants  of 238 

— ,  tsubaki,  constants  of 238 

— ,  ungnadia,  constants  of 238 

— ,  unsaponifiable,     in     cutting     com- 
pounds    487 

— ,  — ,  —  greases 274 

— ,  — ,  —  sulfonated  oil 264 

— ,  valve,  testing  of 254 

— ,  virgin 266 

— ,  walnut,  constants  of 238 

— ,  whale,  constants  of 238 

— ,  — ,  elaidin  test  of 267 

— ,  — ,  testing  of 254 

— ,  wheat,  constants  of 238 

— ,  wintergreen,  in  wintergreen  extract  467 


Oil,  wood    (See  Tung  oil). 

— ,  wool,  constants  of 238 

resisting    test    for    insulating    var- 
nish     229 

soluble  dyes  in  foods 391 

.separation  of 391 

—  varnish    (See  also  Varnish). 

,  analysis  of 217 

Oils,  constants  of  (table) 232 

— ,  heating  value  of 190 

— ,  sulfur  in 191 

— ,  unsaponifiable  matter  in 261 

— ,  animal  and  vegetable,  analysis  of.  .    230 

— ,  fish,  bromine  test  for 254 

— ,  lubricating,  testing  of 254 

— ,  marine  animal,  bromine  test  for.  .  .    254 

— ,  mineral,  testing  of 254 

— ,  wood  preserving,  analysis  of 391 

Oleic  acid,  constants  of 236 

in  oils 242 

Oleomargarine,  analysis  of .  . 427 

— ,  constants  of 236 

—  in  butter 420 

Oleum,  analysis  of 17 

Olive  kernel  oil,  constants  of 236 

—  oil,  adulterants  of 268 

—  — ,  analysis  of 266 

,  constants  of 236,  266 

,  elaidin  test  of 267 

,  Manmene  test  of 267 

Orange  extract,  analysis  of 458 

—  mineral,  analysis  of 210 

,  composition  of 202 

—  oil,  analysis  of 464 

in  orange  extract 460 

—  peel  color,  Albrech  test  for 463 

Ore,  tin,  analysis  of 134 

Organic  coloring  matter  in  red  lead.  .  .    211 

—  matter  in  blanc  fixe,  qualitative  test 

^  for ' 309 

sand  and  gravel . 580 

—  ultimate  analysis 180 

Ostrich  oil,  constants  of 236 

Ottawa    sand       (See    Sand,    standard 

Ottawa). 
Ounces  per  square  yard  from  grams  per 

square  inch,  factor  for 375 

Oven  for  moisture  in  coal 173 

Owala  oil,  constants  of 236 

Oxalic  acid,  0. 1  N  solution  of 8 

Oxide,  spent,  analysis  of 554 

Oxycellulose,  caustic  method  for 365 

— ,  copper  method  for 368 

—  in  cellulose 365 

—  —  cotton  linters : .  .    365 

Oxygen  in  coal 184 

—  absorbed    (See  Oxygen  consumed). 

—  consumed  in  sewage 507,   509 


INDEX 


655 


Oxygen  consumed  in  waters 

—  required    (See  Oxygen  consumed). 


507 


Paint,    green    graphite  pole,     analysis 

of 207 

—  pigments,  classification  of 201 

Paints,  mixed,  analysis  of 200 

Palm  nut  oil,  constants  of 236 

—  oil,  constants  of 236 

Panning  of  tin  ores 135 

Paper,  arsenic  in 40 

— ,  breaking  factor  of 347 

— ,  —  length  of 346 

— ,  bursting  factor  of 349 

— ,  —  ratio  of 349 

— ,  —  strength  of 349 

— ,  chemical  analysis  of 339 

— ,  cross  direction  of 345 

— ,  fiber  analysis  of 337 

—.filler  in 340 

— ,  folding  factor  of 348 

— ,  —  test  of 347 

— ,  glue  in 355,  356 

— ,  machine  direction  of 345 

— ,  microscopic  analysis  of 337 

— ,  Mullen  test  of 349 

— ,  physical  testing  of 345 

— ,  ream  weight  of 350 

— ,  retention  of  filler  in 342 

— ,  rosin  in 356 

— ,  sizing  in 355 

— , ,  detection  of  faulty 358 

— ,  —  (penetration)  tests  of 354 

— ,  starch  in 356,  357 

— ,  strength  factor  of 349 

— ,  —  ratio  of 349 

— ,  —  tests  of 346 

— ,  stretch  test  of 347 

— ,  substance  number  of 352 

— ,  sulfur  in 362 

— ,  —  dioxide  in 342 

— ,  tarnishing  test  of 362 

— ,  tensile  factor  of 347 

— ,  —  strength  of 346 

— ,  thickness  test  of 349 

• — ,  anti-tarnish,  testing  of 362 

— ,  blotting,  absorption  test  of 354 

— ,  cigarette,  composition  of 103 

— ,  coated,  analysis  of 343 

— ,  parchment,  copper  value  of 368 

— ,  wall,  arsenic  in 40 

— ,  writing,  sizing  tests  of 354,  358 

—  testing  machines  347,  348,  349,  350,  352 
Papers,  standard  fiber,  preparation  of.  330 
Para  red  lakes,  composition  of 202 

—  rubber,  20%  compound,  analysis  of.  480 
Paraffin  in  beeswax 278 

—  —  confectionery 419 


Paraffin  scale  in  bituminous  materials 

(reference) 547 

—  wax,  analysis  of 278 

,  constants  of 236 

Parchment  paper,  copper  value  of.  ...    368 

Paris  green,  analysis  of 54 

,  composition  of 54 

with  Bordeaux  mixture,  analysis 

of 52 

—  white,  composition  of 201 

Paste  pigments,  analysis  of 200 

Pat  test  on  hydrated  lime 324 

Pauly  silk 380 

Peach  kernel  oil,  constants  of 236 

Peanut  oil,  arachidic  acid  test  for 250 

,  Bellier  test  for 252 

,  constants  of 232 

,  elaidin  test  of 267 

,  Renard  test  for 250 

Penetration  test  of  bituminous  mater- 
ials     539 

paper 354,  358 

Pentosans  in  cellulose 366 

cotton  linters 366 

feeds  and  grains 442 

Peppermint  extract,  analysis  of 467 

—  oil,  analysis  of 464 

Perilla  oil,  constants  of 236 

Perkins'    Mullen     (bursting    strength) 

tester  (Fig.  18) 349 

Permanganate      (See    also    Potassium 
permanganate) . 

—  method  for  antimony 150,   155 

calcium 326,  518 

chromium  in  steel 122 

formic  acid 81 

nitrites 28 

sumac  extract 479 

tannins 479 

vanadium  in  steel 123 

Peroxide    method   for    chromium    208, 

215,  477 

formaldehyde 79 

sulfur 59,  482 

titanium 128 

Persimmon  seed  oil,  constants  of 236 

Perspiration  test  on  textile  fabrics 376 

Peter  Cooper  standard  glues 321 

Petroleum  hydrocarbons  in  soap 287 

—  products  in  tar,  test  for 547 

Phenacetolin  indicator  solution 100 

Phenol    (See  also  Carbolic  acid). 

Phenolphthalein  indicator 12 

Phenolsulfonic  acid,  preparation  of. ...    505 

method  for  nitrates 505 

m-Phenylenediamine  method  for  citral     461 

Phloroglucid  method  for  furfural 366 

pentosans 366 


656 


INDEX 


Phloroglucinol,  purification  of 366 

—  test  for  ground  wood 338 

Phosphate  method  for  zinc.  .  .147,  216,  304 
Phosphates   (See  also  Phosphoric  acid). 
Phosphoric  acid    (See  also  Phosphoric 
anhydride). 

in  fertilizers 525,  528 

vinegar 456 

.molybdate    method    for,    gravi- 
metric     525 

, ,  volumetric 528 

,  citrate-insoluble 527,  530 

,  —  -soluble 528,  530 

§  water-soluble 527,  529 

•• — anhydride      (See   also      Phosphoric 
acid). 

in  blanc  fixe 311 

salt 25 

Phosphorus  (See  also  Phosphoric  anhy- 
dride). 

—  in  alloy  steel . 118 

brass  and  bronze 143 

coal  and  coke 184 

iron 132 

limestone 327 

steel 112 

— ,  gravimetric  molybdate  method  for     114 

— ,  reduction  method  for 25 

— ,  volumetric  molybdate  method  for 

112,   143 

Phytosterol  in  fats 247 

Phytosteryl  acetate,  melting  point  of .  .    249 

Picric  acid  test  for  gelatin 448 

"Picking"  test  of  coated  papers 343 

Picks  per  inch  in  textile  fabrics 374 

Pig  iron,  analysis  of 129 

,  sampling  of 106,   129 

Pigment  in  greases 273 

mixed  paints . 204 

Pigmented  greases 270 

Pigments,  composition  of 201 

—  in  foods,  classification  of 389 

oil,  analysis  of 200 

— ,  black,  classification  of 201 

— ,  blue,  classification  of 203 

— ,  brown,  classification  of 203 

— ,  green,  classification  of 203 

— ,  red,  classification  of 202 

— ,  white,  classification  of 201 

— ,  yellow,  classification  of 202 

Pipe     covering,     asbestos     magnesia, 

analysis  of 62 

, ,  composition  of 62 

Pistachio  nut  oil,  constants  of 236 

Pitch,  asphaltic,  analysis  of 537 

— ,  coal-tar  roofing,  analysis  of 536 

Plant  ashes,  potassium  in 41 


Platinum,  care  of 14 

—  chloride  solution,  preparation  of 16 

—  cobalt  method  for  color  of  water 497 

Nessler  standards 500 

—  residues,  recovery  of 16 

• —  wire  method  for  turbidity  of  water.    495 

Plum  kernel  oil,  constants  of 236 

Plumbago    (See  Graphite). 

Ply  yarn,  sizes  of 374 

Polarizarion  of  animal  and    vegetable 

oils 250 

honey 421 

maple  products 425 

rosin  oil 249 

sugars. 397 

vinegar .  . . 455 

Pole  paint,  green  graphite,  analysis  of . .  207 
Polenske  number  of  oils 244 

—  value    (See  Polenske  number). 
Polishes,  metal  and  brass,  analysis  of . .     488 

— , ,  composition  of 488 

Polymerization  test  of  turpentine 196 

Polysulfide  sulfur  in  lime  sulfur  solu- 
tion       60 

Poppy  seed  oil,  constants  of 236 

Porpoise  oil,  constants  of 236 

—  jaw  oil,  constants  of 236 

Portland  cement     (See  Cement,  Port- 
land). 

Potash   (See  also  Potassium  and  Potas- 
sium hydroxide). 

— ,  alcoholic,  0 . 5  N  solution  of 1 

— ,  caustic,  analysis  of 21 

— ,  water-soluble,  in  ashes 43 

—  salts,  moisture  in 525 

,  potassium  in 41 

Potassium  in  fertilizers 41 

kainite 41 

plant  ashes 41 

potash  salts 41 

rocks 44 

soils , 44 

— ,  Lindo-Gladding  method  for 41 

— ,  J.  Lawrence  Smith  method  for.  ...      44 
— ,  qualitative  test  for 281 

—  bicarbonate,  analysis  of 19,  22 

in  alkalies 20,  22 

—  bichromate,  analysis  of 30 

,0.1  N  solution 10 

reagent 4 

—  carbonate,  analysis  of 19,  22 

in  alkalies 20,  22 

—  chromate  indicator 12 

—  cyanide,  analysis  of 31 

—  f erricyanide  reagent 4 

—  f errocyanide  in  spent  oxide 557 

—  • — ,  Knublauch  method  for 557 

reagent 4 


INDEX 


657 


Potassium  fluoride  method  for  testing 

aluminum  sulfate .105 

—  hydroxide,  analysis  of 19,  21 

—  —  in  potassium  carbonate 22 

,0.1  N  solution  of 8 

—  permanganate,  0. 1  N  solution  of . .  .        8 

—  sulfocyanate,  0. 1  N  solution  of. ...      11 
reagent 4 

—  thiocyanate     (See  Potassium  sulfo- 
cyanate). 

Pounds  from  grains  per  gallon,  calcula- 
tion of 521 

Pour  test  of  lubricating  oils 25G 

Preece  test  for  galvanizing 164 

Prescott  and  Hess  method  for   couma- 

rin  and  vanillin 468 

Preservatives  in  milk  (reference) 448 

Preserves,  artificial  coloring  in 391 

Proctor-Loewenthal  method  for  tannins 

95,  479 

—  and  Searle  method  for  free  acid  in 

leather 476 

Proof  of  alcoholic  liquids 74 

Protein  in  f eedstuffs  and  grains 439 

milk 444 

Proximate  analysis  of  coal 172 

Prussian  blue,  composition  of 209 

,  extraction  of,  from  spent  oxide. . .    557 

in  green  paint 209 

Pulp    (See  also  Wood  pulp). 

— ,  bleach  consumption  of 313 

— ,  sulfite,  copper  value  of 368 

Pumice  stone  method  for  moisture.  .  .  .    409 

Pumpkin  seed  oil,  constants  of 236 

Pycnometer  method  for  specific  gravity.  230 

—  — ,  Hubbard,  for  specific  gravity.  538,  550 

Pyroligneous  liquor,  analysis  of 368 

Pyrox,  composition  of 52 

Pyroxylin  silk 379 

Quartering  method  of  sampling 167 

Quartz  sand  method  for  moisture . . .  410,  425 

Quicklime,  specifications  for  grades  of.  324 

Quince  oil,  constants  of 236 

Rabbit  fat,  constants  of 236 

"Radiator"  in  water  analysis 498 

Radish  seed  oil,  constants  of 236 

Raffinose  in  beet  products 401 

Rag  in  paper,  detection  of 338 

—  fibers,  stain  for 337 

soda  standard  papers 339 

—  -sulfite  standard  papers 339 

Rape  oil,  constants  of 238 

,  elaidin  test  of 267 

,  Maumen6  test  of 268 

Ratio  number  of  beeswax 276 

Ravison  oil,  constants  of 238 


Reagents,  preparation  of 1 

Ream  weight  of  paper. 350 

scales,  Fairbanks  (Fig.  20) 352 

substance  number  table 353 

Red  lead,  analysis  of 210 

,  composition  of 202 

—  oil,  constants  of 238 

—  pigments,  classification  of 202 

Reducing  substances  in  vinegar 455 

—  sugars,  determination  of 396 

in  vinegar 455 

Reduction  method  for  nitrates 507 

phosphorus 25 

Reductor,  Jones  (See  Jones  reductor). 

Reference  books 627 

Refractive  index  of  oils  and  fats 231 

with  Abbe  refractometer 231 

butyro-refractometer 240 

,  temperature  correction  for 240 

Refractometer,  Abbe,  use  of 231 

— ,  Zeiss  butyro-,  use  of 240 

Refuse  (coal  ash),  analysis  of 185 

Regain  of  silk,  wool  and  cotton 379 

Reichert-Meissl  number  of  butter  fat . .   429 

cocoa  butter 437 

fats 243 

value    (See  Reichert-Meissl  num- 
ber). 

Renard  test  for  peanut  oil 250 

Resazurin  indicator. 103,  105 

Residue    on    evaporation       (See    also 

Solids). 

of  water 497 

Resorcinol  test  for  invert  sugar 423 

Retention  of  filler  in  paper 342 

Rice  oil,  constants  of 238 

Riche  and  Bardy  method    for    methyl 

alcohol 462 

Ring   and   ball   method   for   softening 

point 543 

Road  binder,  bituminous  and  asphaltic, 

analysis  of 537 

—  tars,  analysis  of 554 

Roasting  of  tin  ores 135 

Roberts  needle  for  penetration 539 

Rocks,  potassium  in 44 

Roese-Gottlieb  method  for  fat 418,  445 

Roofing  pitch,  coal-tar,  analysis  of.  ...    536 

Rope  fibers,  classes  of 383 

,  microscopic  examination  of 384 

Ropes,  chemical  tests  of 382 

— ,  fibers  in 383 

— ,  sampling  of 382 

Rosin,  analysis  of 327 

— ,  constants  of • 232 

— ,  grades  of 327 

—  in  beeswax,  test  for 277 

— <•  —  paper 356 


658 


INDEX 


Rosin  in  rosin  size  ...............  329,  330 

--  shellac  .......................    224 

---  varnish  ....................    227 


--  soap 


287 


varnish,  qualitative  test  for  .....  219 

—  ,  iodine  number  of  ................  225 

—  ,  Liebermann-Storch  test  for  ----  219,  356 

—  ,  sizing  tests  of  ...................  328 

—  ,  Twichell  method  for  .............  287 

—  i  yaryan  .......................  •  .  327 

—  anhydride  .....................  .  .  331 

—  oil,  constants  of  ..................  238 

--  ,  polarization  of  ................  249 

--  ,  qualitative  test  for  ............  249 

--  grease  ........................  270 

—  size,  analysis  of  ..................  329 

--  ,  preparation  of,  from  rosin  ......  329 

--  milk,  analysis  of  ...............  332 

Rotation,  optical,  of  lemon  and  orange 

oils  ...........................  464 

—  ,  specific,  of  peppermint  oil  ........  464 

Rubber,  code,  analysis  of  ............  480 

—  extraction  apparatus  (Fig.  25)  ......  481 

—  insulation  compound,  Underwriters' 

Laboratory  method  for  an- 

alysis of  .................  480 

---  ,  20%  para,  analysis  of  ........  480 

Saccharimeter  ......................  397 

—  ,  Ventzke,  angular  degrees  from  .....  465 

Saccharine  products,  analysis  of  ......  408 

Sachsse  method  for  starch  ............  442 

Saffron  oil,  constants  of  .............  238 

Salad  oil  ...........................  266 

Salicylate,     methyl          (See      Methyl 

salicylate). 

Saliva  method  for  starch  in  paper  ......  357 

Salmon  oil,  constants  of  ..............  238 

Salt    (See  also  Sodium  chloride). 

—  in  butter  and  substitutes  .........  428 

--  cheese  ........................  452 

--  soap  ............  .............  285 

—  ,  U.  S.  Standard  for  ...............  24 

—  ,  dairy,  analysis  of  ................  24 

—  ,  table,  analysis  of  ................  24 

Sampling  butter  ....................  427 

—  cheese  .....................  .  ____  451 

—  coal  ............................  167 

—  cotton  (linters)  ...............  .'  .  .  364 

—  fertilizers  .......................  524 

—  iron  .........................  106,  129 

—  lime  ............................  324 

—  Portland  cement  .................  563 

—  rope  and  twine  .........  .........  382 

—  rubber  .....  •.  ...................  480 

—  shellac  ...........................  223 

—  soap  ............................  279 

—  steel  ........................  106,  107 


Sampling  tar 548 

—  white  metals 154 

—  wood  pulp,  A.  P.  and  P.  A.  and  A.  A. 

W.  P.  I.  method 293 

,  Little  method 290 

—  zinc 137 

— ,  alternate  shovel  method  of 167 

— ,  quartering  method  of 167 

Sand,  color  test  for 580 

—  for  concrete 576 

—  in  mortar  and  concrete 559 

— ,  mechanical  testing  of 576 

— ,  organic  matter  in 580 

— ,  standard  Ottawa 571 

—  method  for  moisture 410,  425 

Sanger-Black-Gutzeit    method    for    ar- 
senic   37 

Sanguinella  oil,  constants  of 238 

Sanitary  analysis  of  water  and  sewage .  .  492 

Saponifiable  oil  in  mixed  oils 259 

Saponification  of  wool  grease 275 

—  under  pressure 260 

—  with  aid  of  benzene 259 

—  number  of  oils 241,  259 

rosin 328 

wool  grease 259 

—  value    (See  Saponification  number). 

Sardine  oil,  constants  of 238 

Satin  white,  analysis  of 332 

,  composition  of 332 

in  paper  coating 344 

Sausage,  artificial  coloring  in 391 

Sawarri  fat,  constants  of 238 

Saybolt  universal  viscosimeter 258 

Scale,  boiler,  analysis  of 522 

forming  solids  in  water 520 

Scarlet  lead  chromate,  composition  of .  202 

Schlippe's  salt 34 

Schopper      paper      testing      machines 

(Figs.  16,  17) 347,  348 

Schweitzer's  reagent  for  silk 381 

Screening  test    (See  Sieve  test). 

Screens  for  sand  and  gravel 577 

Seal  oil,  constants  of .• 238 

Searle  and  Proctor  method  for  free  acid 

in  leather 476 

Sediment  in  water 493 

Senega  root  oil,  constants  of 238 

Sesame  oil,  Baudouin  test  for 252 

,  Bellisr  test  for 253 

,  constants  of 238 

,  elaidin  test  of 267 

—  — ,  formaldehyde  test  for 253 

,  furfural  test  for 252 

,  sugar  test  for 252 

,  Villavecchia  and  Fabris  test  for  252 

Setting  test  of  Portland  cement 568 

tung  oil 199 


INDEX 


659 


Sewage,  analysis  of 402 

Shafting  oil,  testing  of 254 

Shark  oil,  constants  of 238 

Shea  butter,  constants  of .    238 

Sheepsfoot  oil,  constants  of 238 

,  elaidin  test  of 267 

Shellac,  analysis  of 223 

— ,  iodine  number  of 225 

— ,  sampling  of 223 

— ,  bleached,  analysis  of 224 

— ,  — ,  forms  of 223 

— ,  orange,  analysis  of 224 

—  varnish,  analysis  of 226 

,  preparation  of 223 

Sheradizing  on  iron  and  steel 164 

— ,  testing  of 163 

"Short  oil"  varnish 220 

Sienna,  burnt,  composition  of 203 

— ,  raw,  composition  of 203 

Sieve  test  of  bone  and  tankage 524 

clay  or  kaolin 318 

gravel  and  sand 577 

Portland  cement 564 

Sieves,  specifications  for 565,  579 

Silex,  composition  of 201 

Silica  in  barium  sulfate,  qualitative  test 

for 309 

black  sulfate  liquor 295 

boiler  scale 523 

green  pole  paint 209 

Portland  cement 574 

sodium  silicate 29 

water 517 

white  sulfate  liquor 298 

—  dishes  for  evaporation  of  vinegar . .  .    484 

—  standard  for  turbidity  of  water ....    494 
Silicate  of  soda    (See  Sodium  silicate) . 

Silicious  matter  in  boiler  scale 523 

Silicon  in  aluminum  alloys 160 

iron 132 

steel 114 

tungsten  steel 126 

—  mixture 115 

Silicotungstate  method  for  nictotine. .      101 
Silk,  basic  zinc  chloride  method  for.  .  .    377 

—  in  cloth  and  yarns 377 

— ,  numbering  of 375 

— ,  regain  of 379 

— ,  acetate 380 

— ,  artificial,  varieties  of 379 

— ,  —    and     natural,    distinction    be- 
tween     379 

— ,  celestron . 380 

— ,  cellulose  acetate 380 

— ,  Chardonnet 379 

— ,  cuprammonium 380 

— ,  gelatin 380 

— ,  Lehner 379 


Silk,  lustron 380 

— ,  Pauly 380 

— ,  pyroxylin 379 

— ,  raw,  sizes  of 375 

— ,  spun,  sizes  of 375 

— ,  viscose 380 

Silver  carbonate,  preparation  of 89 

—  nitrate,  0. 1  N  solution  of 11 

reagent 4 

solution,  ammoniacal 299 

test  for  aldehyde  in  alcohol 75 

blanc  fixe 309 

Sirup    (See  Syrup). 

Sisal    and     Manila    fibers,    distinction 

between 383 

Size  of  yarn,  determination  of 374 

— ,  animal    (See  Glue). 

— ,  rosin,  analysis  of . .  .  329 

— ,  — ,  preparation  of 329 

Sizing  in  paper,  faulty,  detection  of ...  358 

—  materials  in  cloth  and  yarns. . .  .  372,  377 
paper 355 

—  test  of  paper .354,  358 

rosin 328 

Skunk  oil,  constants  of 238 

Slag  for  concrete 576 

Smith    (C.    M.)    method   for   arsenious 

oxide 57 

—  (J.  Lawrence)  method  for  potassium  44 

Soap,  analysis  of 279 

— ,  glycerine 286 

—  in  cutting  compounds 487 

greases 272 

metal  polishes 489 

tallow 270 

— ,  transparent 286 

—  lyes,  glycerol  in 85 

—  method  for  hardness  of  water 511 

—  solution,  standard 511 

thickened  mineral  oil  grease 270 

Sod  oil    (See  Degras). 

Soda    (See  also  Sodium  oxide). 

—  ash    (See  also  Sodium  carbonate) . 

,  analysis  of 20 

lime  for  carbon  dioxide  absorption  : .  109 

—  pulp  fibers,  stain  for 337 

rag  standard  papers 339 

Sodium  in  water 518 

— ,  qualitative  test  for 280 

— ,  total,  in  black  sulfate  liquor 296 

—  arsenite,    0.1    N    solution    of    (See 

Arsenious  acid.) 

—  biborate    (See  Borax). 

—  bicarbonate,  analysis  of 19,  22 

,  conversion  to  carbonate 7 

in  alkalies 20,  22 

—  bichromate,  analysis  of 30 

—  carbonate,  analysis  of 19,  22 


662 


INDEX 


Sucrose     in    lemon    and    orange    ex- 
tracts     462 

• maple  products 426 

saccharine  products 415 

vanilla  extract 471 

• — ,  optical  methods  for 397 

—  solutions,  specific  gravity  of 410 

Sudan  G,  separation  of 392 

—  I,  separation  of 392 

—  II,  separation  of 392 

• —  III,  separation  of 392 

—  IV,  separation  of 392 

Sugar    (See  also  Sucrose). 

— ,  a-naphthol  test  for 417 

• — ,  determination  of 396 

—  in  albumin,  detection  of 94 

soap 286 

— ,  polarization  of 397 

— ,  invert,  determination  of 406,  408 

— ,  — ,  Feder  aniline  chloride  test  for. .  .    424 

— ,  — ,  Fiehe-Bryan  test  for 423 

— ,  — ,  in  honey 423 

— ,  — ,  — maple  products 425 

• — ,  — •-,  resorcinol  test  for 423 

— ,  — ,  volumetric  method  for 406 

• — ,  maple,  analysis  of 424 

• — ,  raw,  analysis  of 396 

• — ,  reducing,  Allihn  method  for 407 

• — ,  • — ,  by  copper  reduction 402 

— , — ,  Defren-O' Sullivan  method  for..   405 
• — ,  — ,  determination  of 402 

• — ,  • — ,  in  cattle  foods 441 

• — ,  — ,  —  vinegar 455 

— ,  — ,  Munson  and  Walker  method  for.  403 
— ,  total,  in  cattle  foods 440 

—  test  for  sesame  oil 252 

Sugars  in  vinegar 455 

Sulfate  of  alumina   (See  Aluminum  sul- 

fate). 

—  ash  of  albumin 94 

• —  process  for  wood  pulp . 294 

—  pulp  cook  liquor,  analysis  of 294 

Sulfates    (See  also  Sulfur  trioxide). 

—  in  alkalies 22 

lime  sulfur  solution 61 

sodium  silicate 30 

Sulfide  in  sodium  sulfide 28 

• —  of  antimony  (See  Antimony  sulfide). 

—  sulfur  in  lime  sulfur  solution 60 

—  test  of  tinned  iron  and  steel. 166 

Sulfides    (See  also  Hydrogen  sulfide). 

— ,  sulfites,   and  thiosulfates,  determi- 
nation of 299 

Sulfite  acid,  analysis  of 301 

,  composition  of 301,  302 

—  fuchsin  method  for  aldehydes. .  .75,  460 

—  pulp,  copper  value  of 368 

fibers,  stain  for 338 


Sulfite-rag  standard  papers 339 

Sulfites    (See  also  Sulfur  dioxide). 

Sulfocyanate,  0. 1  N  solution  of 11 

Sulf onated  oil,  analysis  of 263 

,  preparation  of 263 

Sulf  onation  of  indigo 98 

—  residue  in  carbolineum 533 

dead  oil  of  coal  tar 533 

,  Western  Elec.  Co.  method  for.. .  533 

Sulfur    (See  also  Sulfur  trioxide). 

—  as  polysulfide 60 

— ,  analysis  of 17 

— ,  calorimetric  method  for 191 

— ,  Elliott  method  for 132 

— ,  Escha  method  for 174 

— ,  evolution  method  for 115 

—  in  alcohol 79,  191 

alloy  steel 118 

antimony  sulfide 34 

coal 174 

foods 395 

fuel  oil 190 

gasoline 190 

glue 321 

iron 132 

lime  sulfur  solution 59 

liquid  fuels 191 

paper 362 

rubber  compounds 482 

spent  oxide 555 

steel 115 

— ,  sodium  peroxide  method  for ....  59,  482 

— ,  active,  in  glue 321 

— ,  — ,  —  paper 362 

— ,  free,  in  antimony  sulfide 34 

• — ,  — ,  —  rubber  compounds 483 

— ,  total,  in  rubber  compounds 482 

—  compounds  in  alcohol 79 

,  hydrogen  peroxide  test  for 69 

—  dioxide,  distillation  method  for ....  395 

• in  bisulfites 301 

foods 395 

glue 321 

paper 342 

— . sulfite  acid 301 

—  trioxide    (See  also  Sulf  uric  acid). 

in  aluminum  sulfate 304 

boiler  scale 523 

— chrome  yellow 216 

oleum 17 

Portland  cement 573 

salt 26 

satin  white 333 

sodium  silicate 30 

sulfonated  oils 264 

water 519 

Sulfuretted  antimony    (See     Antimony 
sulfide). 


INDEX 


663 


Sulfuric  acid  in  aluminum  sulfate 304 

formic  acid 81 

glue 321 

leather 475 

sulfite  acid 301 

,  free,  in  aluminum  sulfate 305 

,  — ,  —  leather 475 

,  fuming    (See  Oleum). 

reagent 5 

,  38  normal 197 

"  Sulfuring  "  of  foods 395 

Sulfurous    acid     (See    also    Sulfur    di- 
oxide). 

in  glue 321 

paper 342 

sulfite  acid 301 

Sumac  extract,  analysis  of 479 

Sunflower  oil,  constants  of 238 

Surgical  dressings,  mercuric  chloride  in.     62 

Suspended  matter  in  water. , 493,  516 

Sweeney  method  for  crude  fiber 394 

Swett  test  for  Manila  fiber 383 

Syrup,  coal-tar  dyes  in 389 

— ,  mineral  adulterants  in 414 

— ,  maple,  analysis  of 424 

— ,  sugar,  analysis  of 409 

Table  oil,  ordinary 266 

—  salt    (See  Salt). 

Talc,  analysis  of  (for  paper  filler) 334 

— ,  composition  of 334 

—  in  paper 341 

Tallow,  analysis  of 268 

— ,  beef,  constants  of 232 

— ,  — ,  in  lard,  Emery  test  for 253 

— ,  Borneo,  constants  of 232 

— ,  Mafura,  constants  of 236 

— ,  Malabar,  constants  of 236 

— ,  mutton,  constants  of 236,  269 

— ,  vegetable,  constants  of 238 

—  grease 270 

—  oil  in  cylinder  oil 259 

,  constants  of 238 

—  seed  oil,  constants  of 238 

Tampico  fiber 384 

Tankage,  analysis  of 524 

Tannate  solution  for  color  test  of  sand . .  581 
Tannic  acid    (See  also  Tannin). 

,  analysis  of 95 

in  tannins 96 

Tannin  in  sumac  extract 479 

— ,  Loewenthal-Proctor  method  for .  95,  479 
— ,  permanganate  method  for 95,  479 

—  test  for  glue 94,  355 

Tanning  liquor,  chrome,  CroOs  in 477 

Tannins  in  tannic  acid 95 

Tar,  asphalt  products  in 547 

—  in  cylinder  oils 260 


Tar  in  pyroligneous  liquor 369 

spent  oxide 556 

wood  distillate 369 

— ,  petroleum  products  in 547 

— ,  sampling  of 548 

— ,  coal,  analysis  of 548 

— ,  — ,  in  soap  (reference) 288 

— ,  road,  analysis  of 537 

— ,  water-gas,  analysis  of. .  548 

—  acids  in  carbolineum 534 

crude  tar 554 

gypsy  moth  creosote 536 

wood  preserving  oils 534 

,  Western  Elec.  Co.  method  for  . .  534 

Tarnishing  test  for  paper 362 

Tea  seed  oil,  constants  of 238 

Temperature  coefficient  of  normal  solu- 
tions   87 

—  corrections  for  Brix  gravities 413 

normal  solutions 13 

refractive  index  of  oils  and  fats.  240 

specific  gravity  of  oils  and  fats .  231 

Tensile  factor  of  paper 347 

—  machine,  Schopper  (Fig.  16) 347 

,  cement  (Fig.  29) 570 

—  strength  of  paper 346 

Portland  cement 569 

sand  and  gravel 579 

textile  fabrics 373 

Terra  alba    (See  also  Gypsum). 

,  analysis  of 319 

,  composition  of 201 

Textiles    (See  also  Fabrics,  textile). 

— ,  arsenic  in 40 

— ,  fibers  in 377 

— ,  structural  analysis  of 372 

Theobromine  in  cocoa  and  chocolate .  .  435 

Thermometer  for  gasoline  distillation.  189 

tar  distillation 552 

titer  test 246 

—  stem  correction 194 

Thickness  of  paper 349 

—  gauge  for  paper  (Fig.  19) 350 

"Thief"  for  tar  sampling 549 

Thinner  of  paints,  separation  of 205 

Thinners  in  Japan  drier 221 

varnishes 218 

"  Thio  "    (See  Sodium  thiosulf ate) . 
Thiosulfate    (See  also  Sodium  thiosulf  ate) . 

—  in  lime  sulfur  solution 61 

—  method  for  copper 58 

— ,  sulfite  and  sulfide,  determination  of .  299 

Thread,  twists  per  inch  in 374 

—  count  of  textile  fabrics 374 

—  number 374 

—  size 374 

Tin  in  aluminum  alloys 161 

Babbitt  metals l.r>7,  158 


664 


INDEX 


Tin  in  brass  and  bronze 144 

solder 154 

—  in  tin  ores 134 

type  metals 158 

white  metals 154 

— ,  gravimetric  method  for 144,  154 

— ,  iodine  volumetric  method  for 155 

—  ores,  assay  of 134 

—  oxide,   natural 134 

,  purification  of 144,  154 

,   test  for 134 

—  -stone 134 

Tinning    test,    Am.    Elect.    Ry.    Eng. 

Assoc.  method  for 166 

,  Am.  Tel.  and  Tel.  Co.  method  for  166 

Titanium,  colorimetric  method  for 128 

—  in  steel 128 

— ,  peroxide  method  for 128 

— ,  qualitative  test  for 123,  128 

—  steel,  analysis  of 116 

—  sulfate,  preparation  of  standard..  .  .  129 

Titer  test  of  fatty  acids 246 

Tobacco,  analysis  of 100 

— ,  nicotine  in 103 

—  extract,  analysis  of 100 

—  seed  oil,  constants  of 238 

Toluene-benzene  method  for  free  car- 
bon   551 

Transformer  oil,  testing  of 254 

Tsubaki  oil,  constants  of 238 

Tung  oil,  analysis  of 198 

,  constants  of 198,  232 

Tungsten  in  steel 126 

—  steel,  analysis  of 116 

Turbidity  of  water 494 

— ,  platinum  wire  method  for 495 

— ,  standard  of 494 

Turbine  oil,  testing  of 254 

Turkey  red  oil  (See  also  Sulf  onated  oil) . 

,  constants  of 238 

Turmeric,  dyeing  test  for 390 

—  in  lemon  extract,  test  for 463 

orange  extract,  test  for 463 

Turpentine,  analysis   of,  electric    rail- 
way specifications 196 

— , ,  Forest  Products  Laboratory 

method 193 

—  in  paints 206 

varnish 218 

— ,  temperature  expansion  coefficient  of  194 

—  test  for  artificial  color  in  clay 319 

Turtle  oil,  constants  of 238 

Tuscan  red,  composition  of 202 

Twichell  method  for  rosin 287 

Twine,  asbestos  cotton,  analysis  of. ...  385 

Twines,  chemical  tests  of 382 

— ,  fibers  in 377,  383 

— .sampling  of 382 


Twist  in  thread 374 

Type  metals,  analysis  of 158 

Ucuhuba  fat,  constants  of 238 

Ulsch-Street    method    for    nitric    and 

ammoniacal  nitrogen 68 

Ultimate  analysis  of  coal 180 

Ultramarine,  composition  of 203 

—  in  paper 340 

— ,  resistance  to  alum 336 

— ,  testing  of 336 

Ultraviolet  light  test  for  fabrics 375 

Umber,  burnt,  composition  of 203 

— ,  raw,  composition  of 203 

Underwriters'   Laboratory  method  for 

analysis  of  rubber  compound 480 

Ungnadia  oil,  constants  of 238 

Unsaponifiable  matter  in  oils 261 

rosin :  .  328 

soap 286 

sulf onated  oils 264 

—  oil  in  greases 274 

Unsaponified  oil  in  greases 273 

Uranium  acetate  test  for  sodium 280 

Vacuum  moisture  method 224,  438 

Valve  oil,  testing  of 254 

Vanadium  in  steel 123,  125 

— ,  permanganate  method  for 123 

— ,  qualitative  test  for 123 

—  and  chromium,  double  titration  of. .  125 

—  steel,  analysis  of 116 

Vandyke  brown,  composition  of 203 

Vanilla  extract,  analysis  of 468 

,  U.  S.  standard  for 473 

—  resins,  tests  of 472 

Vanillin  in  vanilla  extract 468 

— ,  Hess  and  Prescott  method  for 468 

Varnish,  black  insulating,  analysis  of.  .  227 

— , ,  specifications  for 227 

— ,  interior,  U.  S.  Navy  specifications  for.  220 

— ,  oil,  analysis  of 217 

— ,  — ,  composition  of 218 

— ,  — ,  physical  tests  of 220 

— ,  — ,  short  or  long  oil  test  of 220 

— ,  shellac,  analysis  of 226 

—  gums 218 

Vegetable  oils  and  fats,  analysis  of ....  230 
,  constants  of  (table) 232 

—  tallow,  constants  of .  238 

Vegetables,  canned,  coal-tar  dyes  in. . .  391 

Vehicle  of  paints,  analysis  of 204 

,  separation  of 204 

—  in  white  lead  paste 211 

Venetian  red,  composition  of 202 

Ventzke  saccharimeter,  angular  degrees 

from 465 

,  polarization  with , 397 


INDEX 


665 


Vermilion,  American,  composition  of .  .  202 

— ,  English,  composition  of 202 

Vicat  apparatus     for     cement     testing 

(Fig.  27) 566 

Villavecchia   and   Fabris  tests  for  ses- 
ame oil 252 

Vinegar,  analysis  of 454 

— ,  coal-tar  dyes  in 389 

• — ,  standards  for 458 

— ,  light,  analysis  of 370 

Virgin  oil 266 

Viscose  silk 380 

Viscosimeter,  Saybolt  universal,  opera- 
tion of 258 

Viscosity  of  dextrin  solutions 92 

glue  solutions 323 

lubricating  oils 258 

varnish 218 

—  with  Dudley  pipette 92,  323 

Volatile  acids  in  glue 320 

vinegar 457 

—  matter  in  coal 173 

• —  thinners  in  Japan  drier 221 

—  • —  —  oil  varnish 218 

Volatility  (See  also  Evaporation  test). 

—  of  bituminous  materials 540 

Volumetric  solutions,  preparation  of . . .  6 

,  standardization  of 6 

,  table  of  equivalents  of 615 

,  temperature  corrections  for ....  13 

Wales  in  hosiery 376 

Wall  paper,  arsenic  in 40 

Walnut  oil,  constants  of 238 

Washing  test  on  textile  fabrics 376 

Water    (See  also  Moisture). 
— ,  clarification  of,  by  aluminum  hy- 
droxide    510 

— ,  mineral  analysis  of 514 

— ,  sanitary  analysis  of 492 

— ,  weight  per  gallon  of 191,  515 

— ,  boiler,  analysis  of 514 

— ,  — ,  grading  of 521 

• — ,  industrial,  analysis  of 514 

— :,  manufacturing,  analysis  of 514 

—  equivalent    of    calorimeter,    deter- 

mination of 178 

—  extract    (See  Water-soluble  matter). 
gas  tar,  analysis  of 548 

—  glass    (See  Sodium  silicate). 

soluble  matter    in    case    hardening 

compounds 485 

lead  arsenate 48 

leather 474 

ropes  and  twines 382 

Wax,  carnauba,  constants  of 232 

— ,  Ghedda    (See  Ghedda  wax). 

— ,  flax,  constants  of 234 


Wax,  Japan,  constants  of 234 

— ,  myrtle,  constants  of .  . 236 

— ,  paraffin    (See  Paraffin  wax). 

Waxes,  constants  of  (table) 232 

Weight  of  textile  fabrics 375 

— ,  ream,  of  paper 350 

Weighting  in  textile  fabrics 372 

Western  Electric  Co.  method  for  car- 

bolineum 530 

Westphal  balance,  use  of 230,  255,  549 

Whale  oil,  constants  of 238 

,  elaidin  test  of 267 

,  testing  of 254 

Wheat  oil,  constants  of 238 

White  lead,  analysis  of 211 

—  • — ,  basic  carbonate,    composition  of 

201,  211 
,  —  sulfate,  composition  of 201 

—  liquor  (sulfate),  analysis  of 298 

—  metals,  analysis  of 154 

—  pigments,  classification  of 201 

Whiting  in  paper 341 

— ,  alba    (See  Alba  whiting). 

— ,  composition  of 201 

Wijs  method  for  iodine  number 241 

—  solution,  preparation  of 5,  242 

,  special  for  shellac  analysis 225 

Wiley  method  for  melting  point  (refer- 
ence)      246 

Wine,  coal-tar  dyes  in 389 

— ,  sulfur  dioxide  in 396 

Wintergreen  extract,  analysis  of 467 

—  oil  in  wintergreen  extract 467 

Winton  method  for  lead  number 426 

Wire,  galvanized,  testing  of 163 

— ,  tinned  steel,  testing  of 166 

Wood,  cellulose  in 289 

—  acid,  crude,  analysis  of 370 

—  alcohol    (See  also  Methyl  alcohol). 

,  analysis  of 71 

in  crude  wood  liquor 369 

pyroligneous  liquor 369 

—  distillate  products,  analysis  of 368 

—  liquor,  crude,  analysis  of 368 

—  oil    (See  Tung  oil). 

—  preserving  oils,  analysis  of 530 

—  pulp,  bleach  consumption  of 313 

,  copper  value  of 368 

in  bales,  sampling  of 291 

rolls,  sampling  of 291 

laps,  sampling  of 291 

,  sampling  of,  disc  method 291 

, .official   method   of   A.    P. 

and  P.  A.  and  A.  A.  W. 

P.  1 293 

, ,  strip  method 291 

,  —  and  testing  of,  Little  method.  291 

1  ground  (See  Ground  wood  pulp). 


666 


INDEX 


Wood  pulp,  mechanical    (See    Ground 

wood  pulp). 

• fibers,  stain  for 337 

—  spirit  in  ethyl  alcohol 78 

Wool  in  cloth  and  yarns 378 

— ,  regain  of 379 

cotton  mixtures,  analysis  of 378 

—  dyeing  test  for  colors  in  foods 389 

—  grease  in  cylinder  oil ,  .  .  259 

,  crude    (See  Degras) . 

,  saponification  of 275 

—  oil,  constants  of 238 

Woolen  yarn,  sizes  of 375 

Worsted  yarn,  sizes  of 375 

Writing  papers,  sizing  tests  of 354,  358 

Wuensch  method  for  free  acid  in  leather 

(reference) 477 

Wuerster's  reagent  for  ground  wood. .  .  .  339 

Xylene  method  for  specific  gravity ....  335 
Xylol    (See  also  Xylene). 

—  method  for  water 271 

Xylose,  Allihn  method  for 408 


Yarn,  count  number  of . . . 


374 

374 

—  fibers,  microscopic  examination  of.  .  384 

—  number 374 

Yarns,  fibers  in ,.  377 


Yaryan  rosin 327 

Yellow  ochers,  composition  of 202 

—  pigments,  classification  of 202 

Zeiss  butyro-refractometer,  use  of 240 

Zinc,  analysis  of 137 

— ,  electrolytic   determination    of    146, 

153,  162 

— ,  grades  of 137 

—  in  aluminum  alloys 162 

sulfate 304 

—  —  Babbitt  metals . 157 

—  • —  brass  and  bronze 146,  151 

Japan  drier 222 

nickel  silver 153 

—  —  solder 157 

soldering  paste 491 

—  —  zinc  dust 141 

— ,  phosphate  method  for.  147,  216,  304,  491 

— ,  sampling  of 137 

— ,  amalgamated,  preparation  of 149 

— ,  available,  in  zinc  dust 141 

—  amalgam,  analysis  of 163 

—  chloride  solution,  basic 377 

iodine  fiber  stain 337 

—  dust,  analysis  of 141 

,  bichromate  method  for 141 

iron  method  for  nitrogen 68 

—  oxide  in  chrome  yellow 216 

—  white,  composition  of 201 


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